text
string | predicted_class
string | confidence
float16 |
|---|---|---|
Complete demographic and histologic details of the TS and ESR patients can be seen in Table 1. Median age of the patients in the TS and ESR populations were both 68.0 years. There was a female predominance to both populations (50.4%—TS and 55.1%—ESR). The three largest ethnic groups in the TS were White, Black, and Hispanic, and they represented 78.6, 9.2, and 5.0% of the population, respectively. Likewise, the ESR population’s three largest ethnic groups were White (79.6%), Black (8.4%), and Hispanic (4.6%). A similar proportion of patients presented with a low median family income (<$50,000) and was noted to be 29.8 and 28.7% in the TS and ESR populations, respectively. The majority of patients were married, 57.3% (TS) and 56.2% (ESR). 87.4% (TS) and 88.3% (ESR) patients were insured. Adenocarcinoma was the predominant histology (61.7%—TS and 67.1%—ESR).
|
study
| 100.0 |
Table 2 contains the demographic, histologic, and treatment details for the TS population for the nine different ethnic groups and used the White population as the reference group. Blacks presented with a younger age, less stage I tumors, less grade I tumors, lower income, higher percentage of adenocarcinomas, less nodes examined, and were less likely to be insured, but their number of nodes positive, nodal density, OS, and LCSS was the same. Their 30 and 90-day mortality did not differ as compared to Whites. Hispanic patients presented with younger age, higher median household income, lower rates of insurance, higher percentage of females, lower percentage of Stage I, more grade 1 tumors, higher percentage of adenocarcinomas, and had less nodes examined, but they had a similar number of nodes positive, nodal density, OS and LCSS. Hispanics had a similar 90-day mortality, but their 30-day mortality was higher than Whites (mean 1.8 vs 1.1%). Of all the ethnic groups, the Japanese presented with a highest mean age (70.9), the highest female predominance (62.3%), and the highest rates of insurance (98.0%), but there was a similar OS and LCSS to Whites. Blacks (58.3%) and Hispanics (59.2%) presented with a lower proportion of patients with Stage I NSCLC as compared to Whites (63.2%), but similar rates were noted in all other ethnic groups. The Other Asian group presented with the highest percentage of adenocarcinomas (78.5%), while American/Alaskan Natives presented with the highest percentage of squamous cell carcinomas (35.6%). The Chinese had the highest proportion of patients receiving a (bi)lobectomy at 86.1%, but the least receiving a pneumonectomy (2.5%) as well as a wedge resection (8.8%). Likewise, the Chinese were least likely to undergo a sub-lobar resection for tumors greater than 2 cm with only 5.0% receiving such treatment. Blacks (8.2), Hispanics (8.5), and Other Asians (8.3) were found to have less mean nodes examined than Whites (9.0), and a higher proportion of patients with positive nodes was noted in the Other Asian group (26 vs 21.8%), but none of the other ethnic groups differed from Whites in terms of the median number of nodes explored or number of nodes positive. The only ethnic group that differed from Whites in regards to nodal density was the Other Asian group, 0.10-Other Asians vs 0.07-Whites. The 30-day mortality was higher in the Hispanic patients, but lower in the Other Race and Japanese ethnic groups. The 90-day survival was significantly higher in the Other Race and Other Asian groups. As compared to Whites, OS and LCSS was significantly greater in the Chinese, South Asian, Other Asian, and the Other Race groups. Unadjusted OS by ethnic group can be found in the Kaplan–Meier survival in Figure 1A.
|
study
| 99.94 |
95% confident intervals are given in parentheses. W is used as reference population. All characteristics differing from the W are in bold-print and have brown colored backgrounds. Otherwise, green and blue depict individual rows are different colors for ease of visualization.
|
other
| 99.9 |
Multivariable analysis (MVA) for OS for TS population can be seen in Table 3. Age (p < 0.0001, HR = 1.029) and male sex (p < 0.0001, HR = 1.453) were significantly associated with OS. OS was significantly better than Whites (HR = 0.693–0.843) in all groups except for AI/ANs, Japanese, Blacks, and Hispanics who had a similar OS. MVA-adjusted OS by ethic group can be seen in Figure 1B. As compared to Connecticut, worse survival was noted in California, Greater Georgia, Iowa, Kentucky, Louisiana, and Utah. OS was not income dependent. Insured patients had a better OS than those on Medicaid (p < 0.0001, HR = 1.286). Married patients had a better OS than divorced (p < 0.0001, HR = 1.191), widowed (p < 0.0001, HR = 1.229), and single patients (p < 0.0001, HR = 1.1215). As compared to Stage I, Stages II–IV were associated with a worse OS with a progressively increasing HR (all p < 0.0001, HR = 1.702–3.273). As compared to patients with adenocarcinoma, all histologies were associated with a worse OS (p < 0.0001 to <0.0008, HR = 1.119–1.564). Using well-differentiated tumors as a reference, all other tumor grades were associated with a worse OS (all p < 0.0001, HR = 1.665–3.273). Segmentectomies and (bi)lobectomies were associated with a better OS than pneumonectomies, p = 0.0011, HR = 0.80; p < 0.0001, HR = 0.72, respectively. Patients who received radiation (p < 0.0001, HR = 1.162) experienced worse OS. Number of nodes examined was associated with better OS (p < 0.0001, HR = 0.988), but number of nodes positive (p < 0.0001, HR = 1.04) and lymph node density (p < 0.0001, HR = 1.429) were associated with worse OS. Compared to year 2007, those patients diagnosed in 2010–2012 had significantly better OS with progressively decreasing hazard ratios. OS by insurance status can be seen in Figure 2.
|
study
| 99.94 |
Multivariable analysis for OS for ESR population can be seen in Table 4. Age (p < 0.0001, HR = 1.034), and male sex (p < 0.0001, HR = 1.506) were significantly associated with OS. OS was significantly better than Whites in the Other Race (p = 0.0051, HR = 0.555) and Other Asian groups (p = 0.012, HR = 0.736), but it was similar in all other ethnic groups. As compared to Connecticut, worse survival was noted in California, Greater Georgia, Kentucky, Louisiana, and Utah. OS was not income dependent. Insured patients had a better OS than those on Medicaid (p < 0.0001, HR = 1.385). Married patients had a better OS than divorced (p < 0.0001, HR = 1.301), widowed (p < 0.0001, HR = 1.292), and single patients (p = 0.0015, HR = 1.121). Increasing tumor size (p < 0.0001, HR = 1.016) and T2 vs T1 (p < 0.0129, HR = 1.107) had a worse OS. Only the right lower lobe location was associated with survival (p < 0.0089, HR = 1.132). In comparison to patients with adenocarcinoma, large cell carcinoma, NSCLC-NOS, and squamous cell carcinoma were associated with a worse OS (p < 0.0011 to <0.0001, HR = 1.15–1.381). Using well-differentiated tumors as a reference, all other tumor grades were associated with a worse OS (HR = 1.572–1.846). Segmentectomies (p < 0.0090, HR = 1.235), pneumonectomies (p < 0.0001, HR = 1.782), and wedge resections (p < 0.0001, HR = 1.301) were associated with a worse OS than (bi)lobectomies. Patients who received radiation (p < 0.0001, HR = 1.36) experienced worse OS. Number of nodes examined was associated with better OS (p < 0.0001, HR = 0.984). Compared to year 2007, those patients diagnosed in 2010 and 2012 had significantly better OS.
|
study
| 99.94 |
Multivariate analysis for LCSS for ESR population can be seen in Table 5. Age (p < 0.0001, HR = 1.023) and male sex (p < 0.0001, HR = 1.393) were significantly associated with LCSS. LCSS was not significantly associated with race or income. As compared to Connecticut, worse LCSS was noted in Greater Georgia, Kentucky, and Louisiana. Insured patients had a better LCSS than those on Medicaid (p < 0.0001, HR = 1.445). Married patients had a better LCSS than divorced (p < 0.0004, HR = 1.301) and widowed (p < 0.0036, HR = 1.200). Increasing tumor size (p < 0.0001, HR = 1.020) and T2 vs T1 (p = 0.0003, HR = 1.213) were associated with a worse LCCS. Only the right middle lobe location was associated with LCSS (p < 0.0469, HR = 0.803). As compared to patients with adenocarcinoma, NSCLC-NOS (p < 0.002, HR = 1.382) and large cell carcinoma (p = 0.0003, HR = 1.543) were correlated with a worse LCSS. Using well-differentiated tumors as a reference, all other tumor grades were associated with a worse LCSS (HR = 1.693–2.171). Segmentectomies (p < 0.0065, HR = 1.329), pneumonectomies (p = 0.0027, HR = 1.781), and wedge resections (p < 0.0001, HR = 1.353) were associated with a worse LCSS than (bi)lobectomies. Patients who received radiation (p < 0.0001, HR = 1.556) experienced worse LCSS. Number of nodes examined was associated with better LCSS (p < 0.0001, HR = 0.978). Compared to year 2007, those patients diagnosed in all other years, except for 2011 had a significantly better LCSS. OS and LCSS by marital status can be seen in Figures 3A,B.
|
study
| 99.94 |
Multivariate analysis for 90-day OS for TS population can be seen in Table 6. Age (p < 0.0001, HR = 1.045) and male sex (p < 0.0001, HR = 1.547) were significantly associated with 90-day OS. 90-day mortality was the same in all ethnic groups. Higher median income (>$75,000) was associated with a better survival. As compared to Connecticut, worse survival was noted in Louisiana and Utah. Insured patients had a better 90-day OS than those on Medicaid (p = 0.0005, HR = 1.359) and those with unknown insurance (p = 0.0003, HR = 2.774). Married patients had a better OS than single (p = 0.0188, HR = 1.239) and unmarried/domestic partner patients (p = 0.0310, HR = 3.523). Right bronchus (p = 0.0001, HR = 2.652), bronchus unknown (p = 0.0012, HR = 6.926), and right lower lobe (p < 0.0001, HR = 1.386) were associated with worse 90-day mortality than the right upper lobe location. As compared to Stage I, Stages II–IV were associated with a worse OS with a progressively increasing HRs (all p < 0.0001, HR = 1.607–4.381). As compared to patients with adenocarcinoma, NSCLC-NOS (p < 0.0034, HR = 1.460), other (p < 0.0001, HR = 2.334), and squamous cell carcinoma (p < 0.0001, HR = 1.436) had a higher risk of 90-day mortality. Using well-differentiated tumors as a reference, 90-day mortality was higher in patients having poorly differentiated, undifferentiated, and unknown differentiated tumors. Pneumonectomies were associated with a significantly higher 90-day mortality than all other resection types (p = 0.0281 to <0.0001, HR = 0.418–0.775), except for sub-lobar, NOS which had a higher mortality (p = 0.0012, HR = 1.885). Patients who received radiation experienced a significantly lower 90-day mortality (p < 0.0001, HR = 0.217). Number of nodes examined was associated with better OS (p = 0.0001, HR = 0.984), but number of nodes positive and lymph node density were associated with worse OS. Similar 90-day mortality was noted to 2007 for years 2008–2012.
|
study
| 99.94 |
In Table 7, a multivariate analysis was performed for the risk of having nodal positivity in patients undergoing a definitive surgical procedure with a T1–T2 tumor <2 cm and at least one lymph node examined. The results were adjusted for type of surgical resection. Age (p < 0.0001, HR = 1.036) and male sex (p < 0.0001, HR = 1.386) were significantly associated with positive nodes. Positive nodes were not associated with any ethnic or income group. As compared to Connecticut, a greater risk of positive nodes was found in Greater Georgia, Hawaii, and Utah. T2 tumor had a higher risk of positive nodes than T1 tumors (p = 0.0004, HR = 1.289). Patients without a married partner (p < 0.0033, HR = 1.376) or without insurance (p < 0.0003, HR = 1.376) were more likely to have positive nodes. Right lower lobe location (p < 0.0353, HR = 1.185) was associated with a higher likelihood of positive nodes than the right upper lobe location. As compared to patients with adenocarcinoma, adenosquamous cell (p < 0.0316, HR = 1.416), large cell (p < 0.0252, HR = 1.426), and squamous cell carcinomas (p = 0.0437, HR = 1.149) had a higher risk of having positive nodes. Using well-differentiated tumors as a reference, nodal positivity was higher in patients having poorly differentiated (p < 0.0001, HR = 2.157), moderately differentiated (p < 0.0001, HR = 1.784), and unknown differentiated tumors (p < 0.0001, HR = 1.802). Number of nodes examined was not associated with nodal positivity. Nodal positivity was less likely in years 2010–2012 (p = 0.0427–0.0027), with a progressively decreased HR (0.821–0.0027).
|
study
| 99.94 |
The purpose of our investigation was to assess difference in outcomes (OS and 30/90 day mortality), presentation, and treatment in nine different ethnic groups who underwent surgical resection of NSCLC. As compared to Whites, the unadjusted OS and LCSS was significantly greater in the Chinese, South Asian, Other Asian, and the Other Race groups. After multivariable adjustment, OS was significantly better than Whites in all groups except for AI/ANs, Japanese, Blacks, and Hispanics who had a similar OS. Despite presenting with higher stage tumors, lower median incomes, lower rates of insurance, less nodes examined, less grade 1 tumors, and lower marriage rates, the OS and LCSS of the Black group were not significantly different than that of the Whites. In comparison to the White group, Hispanics had a similar LCSS, but had an improved OS despite having a higher unadjusted 30-day mortality. Although Hispanics presented with a lower percentage of Stage I patients, lower marriage rates, less nodes examined, and lower rates of insurance, they presented with many better prognostic features compared to the Whites including higher income, lower tumor grades, younger age, higher percentage of female patients, and a higher percentage of adenocarcinomas. The Chinese and Other Asian groups were more likely to receive a (bi)lobectomy than the Whites, but the other ethnic groups largely did not differ in the type of surgical procedure. The reason for the higher 30-day mortality (unadjusted) in the Hispanic population is currently unknown, but the all other populations had a similar or better (Japanese or Other Race) 30-day survival to the White population. Although the unadjusted 90-day mortality was lower in the Other Asian and Other Race populations, there was no difference between the other ethnic groups and the Whites. However, the MVA demonstrated that there was no significant difference between the ethnic groups as compared to Whites. It should be noted that we included stage IV patients in this analysis of patients undergoing a definitive surgical procedure because a satellite nodule in a different lobe of the ipsilateral lung was classified by the AJCC staging as metastatic until 2010 when the new AJCC seventh edition classified this situation as T4 (11). The percentage of each ethnic group undergoing a definitive surgical procedure for Stage IV disease varied from 4.5 to 9.8%. Only the Hispanic group had significantly different percentage of Stage IV patients than the White patients (9.8% of Hispanics vs 6.9% of Whites). Two thousand five hundred sixty three patients with Stage IV tumors underwent a definitive surgical procedure. One thousand six hundred twenty-seven patients were classified as having tumors nodules in different ipsilateral lobes during the years 2007–2009. One thousand one hundred twenty-nine underwent a sub-lobar resection (966 wedge, 92 segmentectomy, and 71 sub-lobar, NOS). Although some patients may have undergone a diagnostic wedge procedure, we assume that most of the remaining patients who did not have tumor nodules in different ipsilateral lobes (N = 936) may have been found to have metastatic disease shortly after their surgical procedure. However, the performance of staging investigations and their timing in relation to surgical procedures is not available in SEER. Nevertheless, after removing the patients who would now be re-classified as having Stage III NSCLC, the numbers were too small for further characterization of these patients by ethnicity.
|
study
| 99.94 |
It is interesting to note that the multivariable analyses for OS in the TS and ESR, and LCSS in the ESR populations yielded similar results to the multivariable analyses for OS in our companion manuscript containing two different lung cancer populations (all patients presenting with NSCLC and those presenting with Stage IV disease). In all four lung cancer populations in both manuscripts, well-established risk factors (12, 13) for OS and LCSS were noted in all multivariable analyses including tumor size, stage, differentiation, gender, age, and t-stage. After adjustment for histolopathologic, gender, age, treatment, and marital variables, all ethnicities in all analyses had similar or significantly better OS and LCSS (ESR group only) compared to the White group. Adenocarcinoma was uniformly associated with a better OS. A consistently lower OS and LCSS were noted for all four lung cancer populations in Greater Georgia, Louisiana, and Kentucky. Similarly, patients in California and Iowa had poorer outcomes except for OS in the Stage IV population in California and OS in the ESR group in Iowa. The reason for the consistently poor outcomes across all stages and presentations in these registries is currently not known, but we believe that the number physician per 100,000 may be a factor because all five states rank in the bottom half of states in terms of the density of total active physicians as well as primary care physicians (14). Of interest, the highly significantly survival decrement (p < 0.0001) for tumor location in the mainstem bronchi in the companion manuscript was less significant in the surgical patients where only the right mainstem (p = 0.01) remained significant for OS in the TS group. There was no OS or LCSS decrement noted in the ESR population for the mainstem bronchi location. However, there was only a small number of tumors associated with the mainstem bronchi (N = 30) in the ESR group. We hypothesize that surgery neutralizes the effects of mainstem bronchi locations because this modality effectively eradicates a location that can cause obstructive pneumonias in a compromised patient group. Interestingly, although the companion paper noted that both lower lobe locations were noted to be associated with decreased OS, only the right lower lobe location was noted to be associated with worse OS in the surgical patients. The association of the lower lobes with worse outcomes has been noted in other investigations (15, 16). Our analysis demonstrates that the worse OS survival in patients having tumor located in the right lower lobe may be due to an increased risk of nodal involvement. Prognosis in all lung cancer populations was improved by being married, not having Medicaid, and being insured, but unlike the previous analysis, income was not correlated with LCSS and OS in the surgical patients in this investigation with the exception of borderline worse of OS in the TS population for those individuals with a median household income of <$50,000 (p = 0.0457). In addition, all lung cancer populations were noted to have a general improvement in OS during the years of this study. The improvement in the surgical populations may have been due to variables that are not contained within SEER such as improved staging, increased use of chemotherapy, and better post-operative care. However, the improved OS in the ESR group would argue against the increased use of adjuvant therapy because chemotherapy would be less likely to be used in this group (17, 18). Likewise, it may be argued that better post-operative care did not contribute to the better OS of the TS population because the 90-day mortality did not improve during the years of this study.
|
study
| 99.94 |
This manuscript was able to assess some treatment-related factors because SEER-18 does contain some variables related to radiation and surgery. Patients receiving pre-operative radiation were excluded because it was felt that this treatment could obscure/improve histolopathologic variables. Because SEER-18 does not contain information pertaining to chemotherapeutic treatment, we deliberately decided to separately assess a surgical sub-group of patients with tumors 4 cm or less without nodal involvement because these patients would be unlikely to receive chemotherapy (17, 18). Furthermore, we decided to investigate LCSS as well in this group of early-stage patients because of their relatively high likelihood of surviving lung cancer and possibly succumbing to other smoking-related causes. Worse OS and LCSS were consistently noted after a pneumonectomy despite multivariable analyses that accounted for histopathologic, patient, and tumor location variables. The adverse survival of patients undergoing a pneumonectomy was identified in recent retrospective study that demonstrated that that the lower survival may be due to an increased risk of distal metastases (19). Although the immune effects of a larger lung cancer procedures such as pneumonectomy as compared to (bi)lobectomy and sub-lobar resections is not known, it has been shown that transthoracic surgery for esophageal cancer as compared to smaller and less invasive surgical procedures (gastrectomy for cancer and cholecystomy for benign gallstones) has been associated with a transient immunosuppression (increased T-cell apoptosis and decreased T-cell cytokine production) during post-operative days 1–3 (20). Interestingly, a different research group noted that both transhiatal and transthoracic esophagectomies were associated with reduced TH1-type cytokine production on post-operative day 1, but depression of Th2-type cytokine was more profound with the latter procedure (21). In both surgical populations, the number of nodes examined was strongly correlated with OS and LCSS and was similarly noted in a past SEER analysis (22). The better outcomes associated with an increasing number of nodes examined may be due to the removal of microscopic disease that may or may not be recognized (especially in the ESR group) by routine pathologic methods (23), but because there is no OS with mediastinal lympadenectomy as compared to nodal sampling (24), one might infer that the beneficial effects of lymph node examination may be due to upstaging cancers that would otherwise be classified as node negative. Post-operative radiation was associated with poorer OS and LCSS. Although past retrospective analyses have demonstrated a possible survival benefit for radiation therapy in patients with N2 disease (25, 26), others have not (27). However, there has been general agreement that post-operative radiation results in a survival decrement in patients with N0 and N1 disease (25, 26). A recent retrospective investigation demonstrated that there was an OS benefit for post-operative radiation therapy for patients who experience a positive resection margin for all nodal stages (28). We would assume that the patients who receive post-operative radiation therapy for nodal stages N0–N1 during the years of our study had a positive margin, but SEER does not have information concerning margin status, and our results show a strongly negative effect of radiation on OS and LCSS in the surgical patients. Although there may be negative selection factors (i.e., positive margin, lymphatic, and/or vascular invasion) in the patients receiving radiation, it may be that radiation therapy has no efficacy and could possibly only have deleterious effects in the post-operative setting, especially in those with N0–N1 disease.
|
study
| 99.9 |
The MVA for 90-day OS revealed that mortality was not related to ethnicity, but was significantly correlated with single/unmarried partner status, Medicaid or unknown insurance, and income. Nevertheless, several known histopathologic and patient prognostic factors associated with aggressive disease/poor outcomes predicted 90-day mortality included increasing patient age, male sex, tumor differentiation, stage, and non-adenocarcinoma histology and suggest that aggressive tumor spread and/or understaging at the time of resection may be the reasons for poor early survival. However, because financial and partnership variables did affect 90-day mortality, one may conclude that patients may be able to improve their short-term survival by better economic and emotional support. Of interest, even after accounting for histopathologic characteristics, tumor locations in the right mainstem bronchus and right lower lobe were associated with a decrement in OS. We hypothesize that operative complications associated with these locations may be a reason why these sites adversely affect OS in the TS and ESR populations. Treatment-related factors related to an increased mortality included the performance of a pneumonectomy and less nodes examined. We decided to include radiation in this analysis because we felt that radiation could possible result in an increased early mortality. Interestingly, radiation was strongly associated with an improved 90-day survival which may be due to patient selection factors which are not acknowledged by SEER including a better ECOG performance status, less co-morbidities, and lower risk of immediate post-operative infections. Early mortality did not improve during the years of our investigation suggesting that post-operative care was not associated with the improved outcomes in surgical patients.
|
study
| 99.94 |
The decision to assess tumors generally considered eligible for a sub-lobar resection (T1–T2 tumors <2 cm in size) was made in order to assess which patients would benefit from a lymphadenectomy. Not surprisingly, nodal positivity was associated with known prognostic factors including advanced age, male sex, t-stage, aggressive histologies (adenosquamous, large cell, and squamous carcinomas), and tumor differentiation. Importantly, it should be noted that ethnicity was not associated with an increased risk of having positive nodes. Although income was not associated with nodal positivity, not being insured and not being married were both strongly associated with having node involvement. Because this analysis revealed that the right lower lobe location was associated with positive nodes, we believe that this may be a reason why this location is associated with a lower OS in both the TS and ESR populations.
|
study
| 100.0 |
We originally performed this analysis to assess the effects of the presentation and outcome differences by ethnicity as compared to Whites in patients undergoing surgical resection for lung cancer. In comparison to White patients, OS, LCSS, and 90-day mortality were similar or better in all ethnic groups for all three analyses. Median household income was largely not associated with OS or LCSS in the TS and ESR patients, but was strongly associated with 90-day mortality. Because this variable was assigned to patients based upon the median county income, we assume this variable may have adversely affected 90-day survival due to the hospital care received in more wealthy and less affluent areas. Of importance, Medicaid insurance and not being married were associated with lower OS and LCSS as well as an increased risk of 90-day mortality. We feel that not Medicaid insurance is more likely to represent an individual’s economic status and demonstrates the importance of having insurance. However, of great interest, is that having Medicaid and not being married are factors that were also associated with an increased risk of nodal involvement. This suggests that economic and psychological factors can possibly be associated with lung cancer biology. Lower socioeconomic status may affect tumor biology through poor nutrition (29). Recently, it was noted that unmarried lung cancer patients had a greater incidence of depression, less social support, and a survival decrement (30), and that the survival decrement noted in patients with new-onset or persistent depression may be more so in early-stage (Stages I–II) than in patients with more advanced stages (31). We feel that our results suggest that the economic effects of not having insurance and not being married are associated with real changes in tumor biology and aggressiveness.
|
study
| 99.94 |
It should be noted that the SEER database lacks may variables that would have been useful for our analysis including smoking history, body mass index, ECOG performance status, lymphatic and/or vascular invasion, patient co-morbidities, chemotherapy administration, type of surgical procedure (i.e., VATS, robotic surgery, and traditional thoracotomy), radiation dose, and radiation field arrangement. However, we have no reasons to think that any of these variables would have influenced our outcomes because we could account for median household income, type of insurance, and most major histopathologic variables.
|
study
| 99.94 |
In summary, the main purpose of our investigation was to assess difference in outcomes (OS and 30/90 day mortality), presentation, and treatment in nine different ethnic groups who underwent surgical resection of NSCLC. As a secondary aim, we also wanted to assess whether tumor biology (nodal involvement) varied by ethnicity. Even in the analyses that were not adjusted for treatment, histopathologic, patient, and marital factors; Blacks and Hispanics had the same OS and LCSS as the White group. We did not find disparities due to ethnicity in patients undergoing surgical resection for NSCLC, but noted that the disparities may be due to having Medicaid insurance and not being married. Because having Medicaid insurance and not being married were associated with lower OS, LCSS and 90-day OS as well as nodal positivity, we feel that economic and psychosocial variables may play a role in the biological aggressiveness of early-stage lung cancer patients undergoing resection in addition to standard histopathologic and treatment variables. Although marriage was equally as important as socioeconomic factors in our assessment, a study from an earlier time period (1989–2003) suggested that lower socioeconomic status was an independent prognostic factor, but marriage was note (32). However, this past investigation by Ou et al. also noted that race was not a prognostic factor in multivariate modeling.
|
study
| 99.94 |
In TS and ESR populations, OS was not different in the two largest ethnic groups (Black, Hispanic) as compared to Whites, but was related to single/divorced status, medicaid insurance, and income (TS population only). Nodal positivity was associated with patients who did not have a married partner or insurance suggesting that these factors may impact disease biology. Economic and psychosocial variables may play a role in survival of early-stage lung cancer in addition to standard histopathologic and treatment variables.
|
study
| 99.94 |
Understanding spoken or written language in real time is essential to our daily life. The ubiquitous presence of long distance linguistic dependencies (e.g., subject—verb dependencies across a relative clause as, for example, in “The director who embarrassed the actor apologized”) indicates that some type of memory representation is needed for successful integration of the dependent items. Although, there has been a long history of investigation into the role of working memory (WM) in sentence comprehension, controversy remains regarding the kind of memory system that is critical for online sentence parsing.
|
other
| 99.7 |
Most studies of the role of WM in sentence processing have focused on capacity demands involved in maintaining constituents prior to integration or maintaining predictions of upcoming syntactic structure (Daneman and Carpenter, 1980; King and Just, 1991; Just and Carpenter, 1992; Gibson, 1998, 2000; Gordon et al., 2001, 2002, 2004; Warren and Gibson, 2002; Fedorenko et al., 2006, 2007; Daneman and Hannon, 2007). For example, capacity-based accounts attribute the standard advantage in speed and accuracy for processing subject relative clauses (SRCs, as in 1a) compared to object relative clauses (ORCs, as in 1b) to increased WM demands imposed by ORC constructions (Gibson, 1998, 2000; Warren and Gibson, 2002).
|
study
| 56.75 |
Sentences like (1a) could be interpreted in a largely incremental fashion. The attachment of the gap in subject position of the RC to “reporter” happens immediately as the verb “attacked” is parsed. However, according to the WM capacity account, comprehenders have to hold “reporter” in sentence (1b) across some new discourse referents (e.g., the object referent “senator”) before attaching it to “attacked” as an object. Thus, the activation of “reporter” decays more in the ORC structure due to more discourse referents being processed and fewer resources being available for maintaining syntactic representations, as there is assumed to be a trade-off between processing and maintenance in most capacity models.
|
other
| 99.7 |
A more recent body of work has focused on interference as an explanation for these effects. These studies emphasize the content of memory representations, rather than the quantity of information that can be actively maintained in memory (Gordon et al., 2001, 2004, 2006; Van Dyke and Lewis, 2003; Lewis et al., 2006; Van Dyke and McElree, 2006, 2011; Van Dyke, 2007). For instance, Gordon et al. (2001, 2004) demonstrated that the standard disadvantage for ORCs compared to SRCs was substantially reduced when the two noun phrases (NPs) prior to the verb had dissimilar referential properties—that is, when the embedded clause NP (e.g., “the senator” in 1a and 1b) was replaced by a pronoun (e.g., “you”) or proper name (e.g., “Joe”). They concluded that their results favored a similarity-based interference account in which memory retrieval was hampered by similarity in the referential properties of the constituent NPs. These findings were not compatible with a pure memory capacity-based account, since the WM loads were the same across noun distinctiveness conditions. Importantly, however, Van Dyke and Lewis (2003) and Van Dyke (2007) have demonstrated that the same nouns may cause more or less interference in sentence comprehension depending on their syntactic roles in the sentence. For example, for sentences (2a and 2b) below, longer processing times at the main verb “was complaining” and greater comprehension errors were observed for sentences like (2b), where the noun phrase (i.e., “warehouse”) was a syntactic subject than when it was the object of a prepositional phrase (as in 2a), although the distances between “was complaining” and its subject “resident” were the same.
|
study
| 99.75 |
Van Dyke and colleagues (Van Dyke and Lewis, 2003; Van Dyke, 2007) attributed this effect to the fact that comprehenders need to retrieve the main clause subject in order to integrate it with the main verb (“was complaining”). The fact that “warehouse” is a syntactic subject in (2b) causes more interference in locating the appropriate subject (“worker”) than when “warehouse” is a prepositional object as in (2a). Relatedly, greater difficulty is observed when the intervening noun phrase has semantic properties that make it more plausible as the subject of the main clause verb. For example, longer reading times and more errors to comprehension questions are observed for sentences like (2c) than (2b), due to “neighbor” being a more plausible subject of “was complaining” than “warehouse.” Thus, these studies demonstrated both syntactic and semantic interference effects during sentence processing.
|
study
| 99.94 |
To explain these and other interference effects, Lewis et al. have advocated a cue-based parsing approach to sentence comprehension (McElree, 2000; McElree et al., 2003; Van Dyke and Lewis, 2003; Lewis et al., 2006; Van Dyke and McElree, 2006, 2011; Van Dyke, 2007). According to this approach, sentence parsing is accomplished through a series of efficient cue-based memory retrievals. The retrieval cues are a subset of the features of the item to be retrieved, and they are derived from the incoming word, context, and grammatical knowledge. Using evidence from both empirical studies and computational modeling, these researchers have suggested that sentence processing is constrained by the degree of interference from non-target constituents, instead of storage demands. Importantly, Lewis and colleagues found that the degree of interference as predicted by the cue-based parsing theory could successfully account for effects observed in previous studies that had been attributed to storage demands, such as longer reading times (RTs) in ORC vs. SRC structures (Van Dyke and Lewis, 2003; Lewis and Vasishth, 2005; Lewis et al., 2006). In addition to the assumption of an extra retrieval in linking the object gap to the relative pronoun in ORCs, this approach suggests difficulty for ORCs due to interference from “reporter” while binding “senator” as the subject of the embedded verb in sentence 1. That is, in the ORC, when processing “attacked,” comprehenders need to retrieve a syntactic subject that is semantically plausible as its agent (Van Dyke, 2007). “Reporter” fits both of these requirements. In contrast, in the SRC, there is no other preceding noun phrase to provide interference.
|
study
| 99.94 |
As the cue-based retrieval approach focuses on interference as the source of difficulty in sentence processing, there is less need to resort to memory capacity as an explanatory factor per se. The move away from capacity accounts is consistent with recent embedded processes accounts of WM, which define WM as the activated portion of long-term memory, together with a very small number of these activated items (e.g., from one to four) within the focus of attention (Lewis, 1996; Cowan, 1999, 2000; Oberauer, 2002; McElree, 2006; Öztekin et al., 2010). In the embedded processes view, information outside the focus is accessed via cue-based retrieval. Consonant with this WM approach, the cue-based parsing model of sentence processing assumes that skilled sentence processing depends on the maintenance of as few as 1–2 chunks of information in WM. Information outside the focus is retrieved through a match of retrieval cues to stored representations. These hypotheses have been supported through a computational implementation (Lewis and Vasishth, 2005; Lewis et al., 2006), and behavioral studies, using a range of methodologies, including self-paced reading, eye-tracking, and speed-accuracy tradeoff techniques (McElree and Dosher, 1989; McElree, 2000, 2006; Van Dyke and Lewis, 2003; Van Dyke and McElree, 2006, 2011; Van Dyke, 2007; Van Dyke and Johns, 2012). The claims from the cue-based parsing approach challenge research pointing to individual differences in WM capacity as a source of sentence processing difficulty (Daneman and Carpenter, 1980; Fedorenko et al., 2006, 2007; Daneman and Hannon, 2007; Unsworth and Engle, 2007). If skilled sentence processing requires at most 1–2 chunks of active memory, this renders moot the claim that poor sentence comprehension is due to low WM capacity.
|
review
| 99.8 |
However, despite the substantial evidence in favor of such a highly limited WM capacity, some criticisms have been raised (Cowan, 2011; Caplan and Waters, 2013). Even among memory researchers who endorse an embedded processes account of WM, there is an ongoing debate about the storage limits of the focus of attention. For example, while McElree and colleagues (e.g., McElree and Dosher, 1989; Öztekin et al., 2010) have estimated the capacity of the focus of attention to be only one chunk of information based on behavioral and neuroimaging results, Cowan (2011) has critiqued these claims and argued for a multi-item focus of attention with a limit of about 3 or 4 chunks. With a larger capacity for the focus of attention, the possibility remains of meaningful individual differences in this capacity. In fact, Unsworth et al. (2014) and Shipstead et al. (2014) have argued, based on a confirmatory factor analytic approach, that a contributing factor to variation in working memory capacity is the capacity of the focus of attention. Therefore, it remains important to examine whether measures of working memory capacity predict comprehension performance, once other relevant factors have been controlled for.
|
review
| 99.75 |
Historically, a substantial body of research has shown a relation between WM capacity measures and the ability to process complex sentences (Daneman and Carpenter, 1980; King and Just, 1991; Just and Carpenter, 1992; Gibson, 1998; Fedorenko et al., 2006, 2007; Daneman and Hannon, 2007; see Long et al., 2006, for a review). Most commonly, these studies have used complex span measures, such as reading span and operation span to index WM capacity (Daneman and Carpenter, 1980; Turner and Engle, 1989). These measures involve both processing and storage components, in that individuals carry out some processing task (e.g., sentence verification in the reading span task or arithmetic computations in the operation span task) while simultaneously maintaining a secondary verbal load (e.g., words or letters). The claim has thus been that these measures reflect a single capacity that can be flexibly allocated to either processing or storage (Just and Carpenter, 1992). In the sentence comprehension domain, storage could involve maintenance of, for instance, lexical items or conceptual representations, and processing could involve, for instance, accessing these representations or assigning thematic roles.
|
review
| 99.9 |
The importance of using WM measures that combine both processing and storage has been emphasized, as other indices of WM capacity such as standard digit or word span, which mainly reflect storage of phonological representations (Baddeley et al., 1998) have typically shown little relation with the ability to process syntactically complex sentences (Waters et al., 1991; Martin and Romani, 1994; Daneman and Merikle, 1996; Caplan and Waters, 1999; Hanten and Martin, 2000; Friedmann and Gvion, 2003; Daneman and Hannon, 2007; Caplan et al., 2013; Kush et al., 2015). Some recent studies, however, have provided some support for a role for phonological storage in complex sentence comprehension (Acheson and MacDonald, 2011; Pettigrew and Hillis, 2014), suggesting that the issue may warrant further attention.
|
review
| 99.6 |
Even though complex span measures have more consistently shown a relation to sentence processing, the source of the WM-language relationship remains unclear, as WM capacity might relate to various aspects of comprehension. For example, Caplan and Waters (1999) showed that many of the findings relating complex span measures to online comprehension ability failed to replicate or did not support the conclusions that had been drawn. In their own work, they found that neither simple span (e.g., digit span) nor complex span measures related to online measures of syntactic processing ability—that is, measures related to the processing of each word as the sentence unfolds. However, these measures did relate to offline processing ability, which involves using the products of comprehension to carry out some task such as matching a sentence to a picture. The implication is that the WM tapped by span tasks is involved in reviewing or checking the results of comprehension rather than the initial interpretation of a sentence. Thus, Caplan and Waters (1999) concluded that for online sentence processing, a WM system specialized for language interpretation is involved. More recent work by Caplan and colleagues (Caplan et al., 2013; Evans et al., 2015) has supported these conclusions.
|
review
| 99.9 |
In contrast to the inconsistent results for complex span measures and simple span measures tapping phonological storage, one measure which has been consistently related to argument integration during sentence processing is the category probe task, an index of semantic short-term memory (STM) in which participants are presented with a word list and asked to judge whether a probe word is in the same semantic category as any list word (Martin and Romani, 1994; Martin et al., 1994; Hanten and Martin, 2000; Martin and He, 2004; Martin, 2005; Harris et al., 2013). Martin et al. (1994); Martin and He (2004) reported a double dissociation between aphasic patients with semantic STM deficits and patients with phonological STM deficits, with the two types of STM deficits having different consequences for sentence comprehension. Aphasic patients with impaired semantic STM but relatively spared phonological retention had difficulty in understanding sentences in which the integration of semantic information of words was delayed rather than immediate. For example, when detecting the anomaly in sentences in which one to three nouns appeared before a verb (e.g., “Rugs cracked during the move”; “Rugs, vases, and mirrors cracked during the move”) relative to sentences in which the nouns followed the verb (e.g., “The movers cracked the rugs”; “The movers cracked the mirrors, vases, and rugs”), performance was equivalent and at a high level when there was only one noun preceding or following the verb, but declined substantially with increasing numbers of nouns before the verb, but remained at the same high level with increasing numbers of nouns after the verb. Similar results were obtained for sentences with varying numbers of adjectives before a noun (“The rusty old red swimsuit”…) vs. after a noun (e.g., “The swimsuit was old, red, and rusty…). In contrast, patients with a phonological STM deficit showed a normal pattern of effects of the delayed vs. immediate integration conditions but had difficulty with sentence repetition (Hanten and Martin, 2000; Martin and He, 2004). Interestingly, the patients with semantic STM deficits performed at a high level and showed no effect of distance on a grammaticality judgment task that varied the distance between words signaling a grammatical error in ten different types of sentence structures (e.g., for verb phrase deletion: “The hopeful young contestants didn't win and neither *was their rather aggressive competitor” vs. “Susan didn't leave despite many hints from her tired hosts and neither *was Mary”). In contrast, one patient who had little deficit in either semantic or phonological STM demonstrated a detrimental effect of distance in this grammaticality judgment task (Martin and Romani, 1994; Martin and He, 2004). Thus, Martin and colleagues put forward a multiple-component model within the language processing domain, with separate capacities for the retention of phonological, semantic, and syntactic information (Martin and Romani, 1994; Martin and Saffran, 1997; Martin and Freedman, 2001; Martin et al., 2003; Martin and He, 2004; Hamilton et al., 2009). According to this model, semantic and syntactic STM capacities, but not phonological STM, are critical for maintaining unintegrated word meanings and syntactic structures during sentence comprehension, respectively.
|
study
| 60.1 |
However, as discussed earlier, the cue-based parsing approach challenges the long-standing assumption that individual differences in WM capacity are a source of the variation in sentence processing ability, and provides an alternative explanation of the prior neuropsychological results. According to the cue-based parsing approach, comprehension difficulty may arise either from variation in the quality of to-be-retrieved representations, or variation in the ability to efficiently use retrieval cues to activate target information and inhibit irrelevant information (Van Dyke et al., 2014). These two accounts point to language experience and executive control ability as playing important roles for determining comprehension ability. Thus, the relation between semantic STM and sentence comprehension might actually reflect underlying deficits in semantic knowledge representations, which resulted in less rich encoding of semantic features during sentence processing. This assumption is partially supported by the finding that even though the patients with semantic STM deficits in Martin et al.'s studies performed well in terms of accuracy on single word semantic tasks, they did show some deficits in latencies on certain timed semantic tasks (Martin and Romani, 1994; Martin and He, 2004). Thus, these patients may have had some mild degree of semantic deficit per se that affected their comprehension. Another possibility is that these patients have a deficit in the mechanism employed for interference resolution. There are findings suggesting that the left inferior frontal region damaged in the patients with semantic STM deficits is crucial for aspects of executive function (Hamilton and Martin, 2005, 2007), i.e., “semantic control” according to Lambon Ralph and colleagues (Jefferies et al., 2007; Whitney et al., 2011) and “selection from competitors” according to Thompson-Schill and colleagues (Novick et al., 2009; Barde et al., 2010), both of which might be involved in interference resolution during sentence comprehension. Thus, to evaluate the multiple capacities hypothesis, it would be important to show that semantic capacity predicts semantic interference resolution, even after taking into account variations in semantic knowledge and executive control.
|
study
| 98.1 |
Thus, far there has been only a single study to investigate individual differences in sensitivity to interference during sentence processing which takes into account variation in language knowledge. Van Dyke et al. (2014) utilized a dual-task paradigm to assess participants' ability to suppress proactive interference from distractors that appeared in a 3-word memory list (e.g., TABLE, SINK, TRUCK) prior to reading the critical sentence. The critical contrast was between the sentences where the verb was manipulated as follows: It was boat that the guy who drank coffee FIXED/SAILED for 2 sunny days. A previous study (Van Dyke and McElree, 2006) with university-level participants demonstrated that when the verb appeared as fixed, participants experienced retrieval interference from the items in the memory list (which are all fixable items). The Van Dyke et al. (2014) study sampled from a broader range of ability levels and administered a comprehensive battery of 24 individual differences measures. After partialling out the variance that each measure shared with a composite measure of IQ (combining the vocabulary and matrix reasoning subtests of the Weschler Abbreviated Scale of Intelligence; Psychological Corp.; Wechsler, 1994/1999), they observed that WM capacity no longer interacted with individuals' sensitivity to interference whereas a receptive vocabulary measure (Peabody Picture Vocabulary Test-Revised; Dunn and Dunn, 1997) did, such that the comprehension for individuals with low vocabulary was more affected by interference. Van Dyke et al. interpreted this result as most consistent with the view that the quality of to-be-retrieved representations (assumed to be reflected in the receptive vocabulary measure) is a critical determinant of sensitivity to interference. In addition, Van Dyke et al. also observed a significant interaction of IQ with sensitivity to interference, which mirrored the effect found with vocabulary: individuals with lower IQ were more affected by interference. This interaction with IQ is difficult to fully interpret in light of the findings suggesting that IQ shares significant variance with WMC and that this shared variance is itself multi-faceted (Engle et al., 1999a,b; Kane and Engle, 2002; Hambrick et al., 2005; Kane et al., 2007; Shipstead et al., 2014; Harrison et al., 2015). Due to the collinearity of fluid intelligence and WM, we included the WAIS vocabulary measure (Wechsler, 1997; WAIS-III, 2002) as a control variable, because this task is generally viewed as a measure of crystallized intelligence, which has less shared variance with WM capacity (Kane et al., 2007). The inclusion of this task provides a means of assessing the role of WM capacity independent of lexical processing ability.
|
study
| 99.94 |
For the executive control hypothesis, several prior studies have supported a role for general executive control (e.g., as measured by the verbal Stroop task) in comprehending garden-path sentences (Novick et al., 2005, 2014; Vuong and Martin, 2014; Hsu and Novick, 2016). Nevertheless, a potential problem with these findings is that the use of garden path constructions, where correct comprehension requires overriding preferred interpretations of words or syntactic structures, may engage resolution processes differently than in unambiguous sentences (i.e., they may be consciously engaged.) Thus, an important contribution of the current study is to provide data on how executive function becomes involved when parsing unambiguous sentences more like those routinely encountered in everyday conversation.
|
study
| 100.0 |
The current study is the first to examine individual differences in resolving syntactic and semantic interference from distractors embedded within a sentence during online processing. Motivated by the studies summarized above, we examined whether interference resolution depends on general WM capacity, STM capacity (phonological or semantic), executive control abilities, and/or aspects of representational quality. Given the ongoing debates about the nature of the WM-sentence comprehension relation, we aimed to test specific hypotheses about the relation between these various tasks and language processing as predicted by different theories. We summarize these predictions in Table 1 with reference to the specific tasks we use to represent each cognitive construct (see Section Methods for task descriptions).
|
study
| 99.94 |
A specific link between syntactic STM capacity and syntactic interference resolution, but not semantic resolution, should also be expected. However, at present there is no appropriate measurement for syntactic STM. Thus, the predictions from the multiple capacities approach focus on the relation between semantic interference and semantic STM capacity.
|
other
| 99.8 |
While the above accounts entail a range of predictions, some differences between them are critical for the present study. The general WM account implies that WM measures will be related to both semantic and syntactic interference, potentially both in online and offline measures. Thus, numerous interactions between WM and sentence effects are predicted. In contrast, the multiple capacities approach predicts that only specific relations will be obtained—for instance, between a measure of semantic capacity and semantic interference resolution but not syntactic interference resolution. Thus, fewer interactions are predicted which follow specific patterns. The language-specific WM approach predicts no relations between WM measures and sentence processing measures, at least in online processing. The cue-based parsing approach predicts that language knowledge and executive function should interact with interference effects. Interactions with capacity measures are generally not expected. However, based on the findings of Van Dyke et al. (2014)—assuming they hold for cases where distractors are embedded within the sentence—interactions with the portion of WM capacity variance related to IQ may occur. This could be predicted for semantic interference, which is the only type of interference examined in the Van Dyke et al. study.
|
study
| 99.94 |
One hundred and twenty undergraduate students (79 females) from Rice University were recruited for this experiment. Each subject participated in two 1.5 h sessions. All subjects were native English speakers without a diagnosed reading or learning disability and normal or corrected-to-normal vision. Informed consent was obtained from each subject in accordance with the guidelines and approval of the Rice University Institutional Review Board. Subjects received credit toward experiment participation requirements for their courses. Eight subjects were excluded from the analysis due to low accuracy in the sentence comprehension task (< 75%).
|
study
| 100.0 |
We used modified versions of the sentences in Van Dyke's (2007) study. There were eighty sets of sentences with four different types of sentences in each set crossing two levels of syntactic interference with two levels of semantic interference (see examples in Table 2 or see Appendix A in Supplementary Material for complete list.) To increase readability, we refer to the low and high syntactic interference conditions as LoSyn and HiSyn, respectively, while the low and high semantic interference conditions are referred to as LoSem and HiSem. The four sentences in a set began with the same introduction region and differed in the intervening region, in which semantic and syntactic interference were manipulated. To avoid potential problems associated with local coherence effects (Tabor et al., 2004), an adverbial phrase was inserted after the intervening region in order to increase the separation between the interfering noun and the main clause verb. Difficulty with local coherence might have arisen particularly in the low syntactic interference conditions as the interfering NP would have appeared immediately before the main clause verb without the adverbial phrase. The main verb for the long-distance dependency was identified as the critical region, as this is the point at which comprehenders would attempt to retrieve the subject NP. The phrase following the main verb is termed the spillover region, because it is often the case that effects in one region spill over to the next region in self-paced reading (Just et al., 1982).
|
study
| 100.0 |
Eighty sets of four sentences were constructed containing the four types of intervening clauses (see Appendix A in Supplementary Material). The mean length of the experimental sentences was 15.7 words (SD = 1.3 words). To avoid repetition of the verbs and sentence content within one subject, the four items in each set were assigned to four lists and each subject received only one list containing one item per set in a list. Two pseudo-randomized sequences were created for each stimulus list, resulting in a total of eight lists. Each subject saw 20 target sentences in each of the four conditions. Additionally, 80 filler items were added to each list consisting of 36 sentences with a relative clause structure (16 with ORC) and 44 non-RC sentences with right-branching structures. The ORC sentences were included in order to distract subjects from detecting the target sentences. In all, each subject saw 160 sentences during the experiment.
|
study
| 100.0 |
Stimuli were presented in a phrase-by-phrase, non-cumulative, self-paced fashion (Just et al., 1982). Ten practice sentences were presented prior to the experimental sentences, consisting of 4 sentences in the same format as experimental sentences and 6 fillers. Participants were instructed to read each sentence for comprehension silently at a natural pace and told that there would be a comprehension question after each sentence. All trials began with a fixation point appearing in the center of the screen for 1,000 ms, followed by the first phrase. Participants pressed a button with their index finger to bring up the phrases in each sentence, and a period was presented together with the last phrase. The reading time (RT) was recorded as the time between stimulus onset and button press for each phrase. After each sentence, a comprehension question was presented. For the experimental sentences, the phrase probed the critical subject-verb integration (e.g., for the example sentences, “Who will visit?”). For the filler sentences, the comprehension questions probed other noun phrases in the sentence (e.g., for the filler sentence “The artist who feared that the publicist would cancel the exhibit quit on his own,” the comprehension question was “What might be canceled?”). Subjects were required to provide a spoken response, and speed for answering the question was measured through a voice key trigger as the time between question onset and the time when subjects start producing vocal response. The next sentence started after an inter-trial interval of 1,000 ms.
|
study
| 100.0 |
The category probe task (Martin et al., 1994) was included to tap subjects' semantic STM. In this task, subjects were presented with an auditory word list. After a short pause, they heard a probe word and had to judge whether this word was in the same category as any of the words in the list (all of the words in a list were drawn from different categories). Before testing, subjects were shown a list of all nine categories (e.g., animals, clothing, fruits, etc.) that would be presented in the experiment as well as all the words belonging to each category. The number of words in each list ranged from 4 to 7 and there were 24 lists at each list length. The dependent measure was overall accuracy for each subject.
|
study
| 100.0 |
The digit span task from Wechsler Adult Intelligence Scale-third edition (Wechsler, 1997) was included to tap subjects' phonological STM. Participants heard a list of digits and they were required to repeat the numbers aloud in order at the end of each list. The number of digits in each list ranged from 3 to 9, and there were 2 trials at each level. Each subject completed all 14 trials. Overall accuracy was calculated for each subject.
|
study
| 99.94 |
The automated version of Operation Span (Unsworth et al., 2005) was used to measure WM capacity. Subjects were instructed to solve a math operation [e.g., (1 * 2) + 1 = ?] as quickly as possible and then remember a single letter. During this task, a math operation was presented on the screen first. After subjects solved it and clicked the mouse, a digit appeared and subjects judged whether it was the correct answer. After a mouse click response, a letter to be recalled was shown on the screen for 800 ms. This to-be-remembered letter was followed by either another math operation-letter combination or the recall screen, which showed up at the end of each set of operation-letter pairs. At recall, subjects clicked a box next to the appropriate letters in the current set in the order presented. The experimental trials contain three trials at each set size, with set sizes ranging from 3 to 7 items, resulting in a total of 75 trials. The order of set sizes was random for each participant. We evaluated subjects' operation span by the total number of letters recalled in the correct serial position regardless of whether the entire trial was recalled correctly.
|
study
| 100.0 |
We used the automated version of reading span (Unsworth et al., 2005) modified from Daneman and Carpenter's (1980) original version. The task is very similar to the operation span task, but instead of solving math operations, subjects are instructed to judge whether a presented sentence makes sense or not (e.g., Andy was stopped by the policeman because he crossed the yellow heaven.). After pushing a button to indicate whether the sentence makes sense, a to-be-remembered letter is shown on the screen for 800 ms, which is followed by either another sentence-letter combination or the final recall screen. Set sizes ranged from 3 to 7 items. At the end of each set of sentences, subjects recalled all the letters in the current set in order by clicking boxes next to letters. This results in a total of 75 trials; the order of set sizes was random for each participant. We evaluated subjects' performance with the same scoring procedure as operation span.
|
study
| 100.0 |
The standard verbal Stroop task (Stroop, 1935) was adopted in the current experiment to measure subjects' resistance to interference. Subjects were required to name the ink color in all conditions. In the congruent condition, a color word appeared in the congruent color (e.g., the word “blue” in blue ink) while in the incongruent condition, a color word was presented in a different ink color (e.g., the word “blue” in red ink). In the neutral condition, a series of colored asterisks was presented. There were 65 incongruent trials, 77 neutral trials, and 12 congruent trials. Response naming latencies were recorded from the onset of the stimulus through a voice key response. The Stroop interference score for each subject was calculated by subtracting the mean correct RT in the neutral condition from that in the incongruent condition.
|
study
| 100.0 |
The vocabulary subtest of the WAIS-III (Wechsler, 1997) was administered as a measure of verbal knowledge. The test requires subjects to provide word definitions (e.g., Tell me what confide means). We began the vocabulary test from the 12th item in this subtest because the words before the 12th were not discriminating enough for our undergraduate students. Twenty-two words were presented. The test was scored based on the standard scoring criteria in the WAIS-III manual. Each definition received either 0, 1, or 2 points.
|
study
| 99.5 |
Testing was carried out in two sessions, each lasting ~1.5 h for a total of 3 h. A button box with millisecond accuracy was used for the computerized tasks and a voice key was attached to the button box to record verbal responses. The sentence reading, category probe, digit span, and Stroop tasks were conducted on a Macintosh with PsyScope (Cohen et al., 1993). The reading span and operation span tasks were run using E-Prime (Schneider et al., 2002). The task administration order was fixed for all participants: sentence comprehension task first, followed by digit span, Stroop, vocabulary, category probe, reading span, and operation span.
|
study
| 99.94 |
The sentence comprehension experiment produced four dependent variables: reading times (RT) from self-paced reading in the critical region (main verb) and spillover region (the phrase following the main verb), and speed and accuracy for answering comprehension questions. For all RT analyses (i.e., self-paced reading and question answering speed), only data from accurate trials were included. Outliers were calculated by condition for each subject and reading times >2.5 standard deviations away from the mean for each condition were removed from the analyses. The trimming removed 4% of the data in the critical region, 4% of the data in the spillover region, and 5% of the data in the question answering times.
|
study
| 100.0 |
Because some researchers have claimed that variations in processing speed account for the correlations between WM capacity and performance on complex cognitive tasks (Fry and Hale, 1996; Salthouse et al., 2003), a logarithmic transformation was performed on the RT data in order to remove the effects of speed on the size of effects (Verhaeghen and De Meersman, 1998). This transformation also yields more normally distributed RTs than raw RTs, and thus the transformed data better meet the assumptions underlying the general linear model (Baayen and Milin, 2010)1.
|
study
| 100.0 |
The log-transformed RT and error rate data were modeled in linear mixed-effects models (LMEMs) using R (2.11.1) implemented within the lme4 package, with a logistic linking function for dichotomous variables such as comprehension error rate (Baayen, 2008, 2011; Baayen et al., 2008) following guidelines set out by Baayen (2008). Each of the independent variables was mean-centered prior to analysis. This centering allows us to interpret results by making effects analogous to ANOVA results. The semantic and syntactic interference were coded with the low interference condition as −1 and high interference condition as 1. Thus, negative coefficients for each main effect of log RT or error proportion signify worse performance (i.e., longer RT) in the high interference conditions.
|
study
| 100.0 |
In the mixed-effects models, fixed effects included the main effects and interaction of semantic and syntactic interference manipulations, as well as the main effects of all the individual differences and their interactions with semantic/syntactic interference. In addition to these fixed effects, all the mixed-effects models included maximal random-effects structures to provide the most conservative assessment of the significance of results (Barr et al., 2013). Thus, by-subject adjustments to the intercept as well as by-subject adjustments to the random slope of interaction between semantic × syntactic interference were included in the models. Similarly, by-item adjustments to the intercept and to the random slope of interaction between semantic × syntactic interference were included. In addition, word length was included as a control factor in all the models for the critical and spillover regions. There was no convergence problem for any of the models reported in this study. Throughout, we present coefficient estimates, standard errors (SE), and t- or z-scores (when the dependent measures is a dichotomous variable, i.e., accuracy) derived from 50,000 Monte Carlo Markov Chain (MCMC) runs. For the RT data, the degrees of freedom are not reported because they can only be approximated in LMEMs, and consequently p-values are not reported. The t- or z-score based on MCMC sampling and t- or z-score based on the upper bound of the degrees of freedom tend to be very close for a relatively large sample (Baayen et al., 2008). Hence, we adopted a standard in which an absolute t- equal to or >2.0 was considered to be significant at the α = 0.05 level. For the mixed logistic regression analysis of errors, degrees of freedom can be calculated and thus, p-values are reported in the results for these analyses.
|
study
| 100.0 |
Range, mean, and standard deviation for each individual differences measure are shown in Table 3. Reliabilities are also reported as the extent of relation between two variables is limited by the reliability of the measures involved (Schmitt, 1996). For most measures, internal reliability was calculated as the split-half correlation adjusted with the Spearman–Brown prophecy formula (Cronbach, 1951). For operation span and reading span, the internal reliability was obtained from previous studies (Redick et al., 2012). Although, most subjects tended to perform well in most tasks, their scores were distributed widely on each scale and the reliability of all these tests was very high.
|
study
| 100.0 |
The correlations among the individual differences measures are shown in Table 4. Reading span and operation span had a moderately high correlation (r = 0.54), which is consistent with previous studies (as reported by Redick et al., 2012, mean r = 0.64). The category probe measure had low but significant correlations with reading span, operation span and vocabulary. The correlation between digit span and category probe was very low (r = 0.11), substantiating the claim that these measures tap different aspects of STM. Digit span was correlated significantly with reading span and operation span, which is consistent with other evidence showing a phonological component to these WM measures (Kane and Engle, 2003; Camos et al., 2011, 2013). In addition, Stroop correlated with both reading span and operation span, also in line with previous findings (Kane et al., 2001), but did not correlate with digit span or category probe. This pattern may be attributed to the attentional control component (i.e., interference resolution ability in the Stroop task), which is more prominent in complex span measures than in simple span measures (Engle, 2002; Kane and Engle, 2003; Engle and Kane, 2004; Unsworth et al., 2009). Lastly, vocabulary had low to moderate correlations with all of the measures except digit span and Stroop.
|
study
| 99.94 |
Mean error rates and response times for comprehension questions and mean self-paced reading times for the main verb (i.e., critical region) and the following phrase (i.e., spillover region) are shown in Table 5. Subjects generally performed well on the comprehension questions (overall accuracy = 87%). The reliability of each sentence comprehension dependent measure was calculated as a split-half correlation adjusted with the Spearman–Brown prophecy formula (Cronbach, 1951). The reliability of all the dependent measures was very high (≥0.78; see Appendix C in Supplementary Material). As expected, subjects showed the lowest error rate (8%) and shortest question answering time (mean = 1,265 ms) in the LoSyn/LoSem interference condition, and the highest error rate (18%) and longest answering time (mean = 1,436 ms) in the HiSyn/HiSem interference condition.
|
study
| 100.0 |
To obtain a more reliable and robust measure for general WM capacity and to avoid the collinearity issue between reading span and operation span, we computed a composite WM measure by averaging z-scores for the two complex span measures, resulting in a measure which would increase measurement precision of the overlapping component (Nunnally et al., 1967). In order to examine the unique contribution of general WM, specific STM, or executive function as measured by each cognitive ability task, all the individual differences measures were included in the mixed-effects models simultaneously. That is, to determine whether span measures contributed to the prediction of performance beyond what could be predicted on the basis of verbal knowledge, the main effect of vocabulary and its interactions with semantic or syntactic interference as fixed effects were included in all the models with other individual difference measures. Because of the potential concern about mild multicollinearity among the individual differences measures, we also report in Appendix B in Supplementary Material the output of mixed-effects models with each individual differences measure alone (with vocabulary as a control variable)2. Generally, the single predictor analyses provided convergent results to the multiple predictor analyses. Thus, we will only focus on the results from multiple predictor analyses, which revealed the unique contribution of each predictor when controlling for the others.
|
study
| 100.0 |
For these analyses, we focused on the interaction between semantic/syntactic interference and the individual differences measures. In general, individuals with higher capacities or better interference resolution ability should show less difference between high vs. low interference conditions relative to subjects with lower capacities or poorer interference resolution ability. These effects should show up as significant interaction terms (i.e., interference manipulation × individual difference measure) in the mixed effects models.
|
study
| 100.0 |
Semantic/syntactic interference effects and main effects of each individual differences measure are shown in Table 6, and the interactions between sentence processing and individual differences measures are shown in Table 7. Both semantic interference (t = 2.56) and syntactic interference (t = 2.03) effects were significant in the spillover region, whereas neither was significant at the critical verb (semantic: t = 1.94; syntactic: t = −0.02). The interaction between semantic and syntactic interference was not close to significance in either region. The time course of these effects is different from that observed in Van Dyke (2007), in which the syntactic interference effect was obtained at the critical verb, whereas the semantic interference effect was only observed in the final region (after a spillover region). The discrepancies between the results of the current study and Van Dyke's (2007) study may be explained by methodological differences. For one, the current study utilized a self-paced reading paradigm, while the Van Dyke (2007) study provided eye-tracking data. As effects in self-paced reading often spill over into regions following the critical manipulation (e.g., Just and Carpenter, 1992; Bartek et al., 2011), it is possible that an earlier occurring syntactic interference effect may have only become evident in the spillover region. On the other hand, a much larger sample size was used here, which may have made provided the power to detect semantic effects earlier.
|
study
| 99.94 |
These results were from the mixed-effect model analyses including all individual differences predictors. The results of interactions between individual differences measures and semantic/syntactic interference effect are reported in a separate table (see Table 7.)
|
study
| 100.0 |
Vocabulary was included as a control variable. A coefficient is a significant predictor of RT or accuracy of comprehension question at p < 0.05 with criterion that |t| > = 2 or |z| > = 2. The significant predictors are marked with a asterisk and also highlighted in red color.
|
study
| 100.0 |
With respect to individual differences effects, while the main effect of syntactic interference was not significant in the critical region, there was a significant interaction between syntactic interference and the composite WM measure in this region (t = −2.09), which also appeared in the spillover region (t = −2.47; See Figure 1 for a plotting of interaction effects using methods outlined by Dawson, 2014). These interactions indicate online effects of general WM capacity, where those with lower spans tended to have more difficulty with syntactic interference than those with higher spans, with the difference between the high and low span subjects being greatest in the high syntactic interference condition. On the other hand, the interactions between semantic interference and the individual differences measures failed to reach significance in either region. There was also a significant interaction between syntactic interference and digit span in the spillover region, which went in the direction opposite that predicted, indicating that subjects with higher digit span showed larger syntactic interference effects (t = 2.27). However, we suggest that digit span acted like a suppressor variable in the WM-syntactic interference relation, rather than playing a crucial independent role. This conclusion is based on the grounds that when digit span was included as a single predictor in the mixed-effects model analysis (with vocabulary as a control variable; as shown in Appendix B in Supplementary Material), the interaction between digit span and syntactic interference was not significant in either the critical region (t = 0.47) or spillover region (t = 1.623), while the interaction between the WM composite and the syntactic interference effect was marginally significant in both the critical (t = −1.66) and the spillover region (t = −1.99). Therefore, because digit span did not play an independent role and the weight for the composite WM measure became higher when including digit span (i.e., when removing the contribution of phonological retention to the composite WM measure), the influence of digit span fits the definition of a suppressor variable. Last, due to the potential concern that the type of WM task affects the observed relations between WM capacity and other cognitive functions (e.g., Shipstead et al., 2014), we also constructed two other models in which only the reading span or operation span measure was included along with all of the other individual differences measures to investigate whether the specific processing component in each complex span measure (i.e., sentence reading in the reading span task and arithmetic computation in the operation span task) modulated the WM-language relation as reported in some previous studies (Unsworth et al., 2009). The results of these two models were very similar to those from Model 1 in terms of the pattern of main effects and interactions (see Appendices D,E in Supplementary Material for full model output). Although, the relations between reading span and syntactic interference were somewhat stronger than those between operation span and syntactic interference, adding reading span to the model with operation span did not significantly improve the fit (see Appendix F in Supplementary Material). Thus, it appears that the interactions between WM and syntactic interference are due to the overlapping variance between reading span and operation span.
|
study
| 100.0 |
Significant interactions in mixed-effects analysis for individual differences measure with interference effects (see Dawson, 2014, for plotting methods). For RTs (a1,a2,b1), the points plotted for low and high capacity subjects are for −1 and +1 standard deviation from the mean on the composite WM measure or semantic STM measure. For error rates (b2), the values of the interference effect size (on x-axis), ranging from (−1.5) to (1.5) standard deviations from the mean, were calculated in 0.25 std units, with a line fitted to these effects. Panels (a1,a2) show the Syntactic interference × WM composite score interaction in self-paced reading time (ms) in the critical region (“will visit”) and the spillover region (“the director”), respectively. Panel (b1) shows the Semantic interference × Category probe interaction in question answering speed. Panel (b2) shows the Semantic interference × WM composite and Semantic interference × Vocabulary interactions in question answering error rates. The scatter plots with data points from each subject are shown in Appendix G in Supplementary Material.
|
study
| 100.0 |
The findings were in line with previous studies using a similar paradigm in showing semantic and syntactic interference effects in self-paced reading measures (Van Dyke and Lewis, 2003; Van Dyke, 2007). More critically, the present study provides the first evidence that the size of the syntactic interference effect is related to a measure of general WM capacity, and this relation was observed at both the critical and the spillover regions. However, despite the fact that a marginal main effect of semantic interference was obtained in the critical region and a significant effect in the spillover region, no interaction between semantic interference and any of the individual differences measures was observed. It should be noted that the significant interactions between WM capacity and syntactic interference could not be attributed to either verbal knowledge (as measured by WAIS vocabulary) or general executive control ability (as measured by Stroop) as these WM effects were significant even though vocabulary and Stroop were included in the models. Neither vocabulary nor Stroop showed significant interactions with syntactic interference. One might question whether the absence of interactions with vocabulary or Stroop resulted from the significant correlations of these measures with the two WM measures, and thus inclusion of the WM measures masked their influence. However, as shown in Appendix B in Supplementary Material (which presents single variable models with vocabulary as a control variable), when vocabulary and Stroop were included in a model without the other STM or WM measures, no significant interactions were observed with syntactic or semantic interference for either measure (all ts < 1).
|
study
| 100.0 |
The results of main effects and interactions of both experimental manipulations and individual differences measures are shown in Tables 6, 7. For comprehension question error rates, the mixed-effects analysis revealed significant main effects of both syntactic and semantic interference, with a higher error rate for the HiSyn compared to the LoSyn conditions (0.15 vs. 0.10), and a higher error rate for the HiSem compared to the LoSem conditions (0.15 vs. 0.10). The interaction of semantic and syntactic interference was not significant. For question answering RTs, there was a significant main effect of syntactic interference with slower responses in the HiSyn than the LoSyn condition (1,359 vs. 1,325 ms), and a main effect of semantic interference, with slower responses in the HiSem condition than the LoSem condition (1,411 vs. 1,273 ms). The interaction was not significant.
|
study
| 100.0 |
With respect to the individual differences interactions of primary interest, for RTs, there was a reliable interaction between the semantic interference effect and category probe span (t = −2.31)4, indicating that participants with better semantic STM were less distracted by a semantically plausible intervening NP in the HiSem conditions (as shown in Figure 1b1), even after controlling for vocabulary. None of the interactions with other individual differences measures was significant. For error rates, the interaction between the composite WM measure and semantic interference was significant (t = −2.13, p = 0.03), such that those with higher WM capacity showed smaller semantic interference effects. There was also a significant interaction between vocabulary and semantic interference (t = 2.12, p = 0.03), with those with higher vocabulary scores showing larger interference effects, which was opposite the effect reported in Van Dyke et al. (2014). Both interactions are displayed in Figure 1b2. Unlike the case for digit span, the negative weight for the interaction with vocabulary could not be attributed to a suppressor effect, as the same pattern was obtained in the model with vocabulary as a single predictor (see Appendix B in Supplementary Material). One might postulate that those with larger vocabularies have tighter links among concepts, resulting in greater spreading activation and more interference. It is not transparent why those with greater vocabularies showed larger interference effects in the present study whereas in the Van Dyke et al. (2014) study, those with larger vocabularies were less affected by an interfering external load. Of course, there are many differences in the two studies including the type of manipulation (i.e., external load vs. sentence-internal interference), the sentence structures, and the measure of vocabulary (i.e., expressive vs. receptive vocabulary). Thus, future work would be needed to tease apart the source of the difference pattern of effects for vocabulary.
|
study
| 100.0 |
Robust effects of semantic and syntactic interference were observed for both RTs and error rates in question answering. For question answering speed, an interaction between the semantic STM measure (category probe) and semantic interference was obtained. For question answering error rates, the interaction between semantic interference and the composite WM measure, and the interaction between semantic interference and vocabulary were significant5.
|
study
| 100.0 |
Overall, these results provided further evidence demonstrating both syntactic and semantic interference effects during sentence processing (Van Dyke and Lewis, 2003; Van Dyke and McElree, 2006, 2011; Van Dyke, 2007; Glaser et al., 2013; Van Dyke et al., 2014). Participants were slower to read phrases and less accurate and slower to answer comprehension questions with high semantic or syntactic interference.
|
study
| 100.0 |
Of particular interest for the current study are the implications of the interactions between individual differences measures and sensitivity to interference for theories of the relation between WM and sentence processing (see Table 1). Table 8 indicates the significant interactions that were obtained. The discovery of an interaction of syntactic interference with the WM composite in reading times is an important finding, as no study has yet examined individual differences with respect to this type of interference. This finding is inconsistent with both the general WM and language-specific WM approaches. That is, the general WM approach predicted interactions between the composite WM measure and both syntactic and semantic interference during online processing and question answering, whereas the language-specific approach would not have predicted WM to be related to either type of interference in online measures.
|
study
| 100.0 |
With respect to the multiple capacities approach, the results were mixed. Consistent with this approach, the category probe measure of semantic STM interacted significantly with semantic but not syntactic interference in question answering RTs, even when a measure of verbal knowledge (i.e., WAIS vocabulary) was included as a control variable. Thus, semantic capacity per se beyond semantic knowledge related to semantic interference. Moreover, the measure of phonological retention (digit span) did not interact in the predicted direction with any measure. The specific relation of the composite WM measure to syntactic but not semantic interference sensitivity in self-paced reading might also be seen as consistent with the multiple capacities view, to the extent that the complex span measures tap a retention capacity that is more relevant to syntactic than semantic processing. However, the interaction of the complex span measure, but not the semantic STM measure, with semantic interference in accuracy is inconsistent with this view.
|
study
| 100.0 |
The results with respect to the cue-based parsing approach are also mixed. The significant interaction between syntactic interference and the WM composite in the critical and spillover regions, together with the interaction of complex span with semantic interference in question answering, appear to contradict the assertion that WM capacity per se is not involved in sentence processing (e.g., McElree et al., 2003; Van Dyke et al., 2014). The Van Dyke et al. study, which is the only other study to examine individual differences in sensitivity to interference, albeit semantic interference from distractors outside the sentence, did not find an interaction with IQ-partialled complex span tasks, however they did observe an interaction with IQ, which shares significant variance with complex span measures. Thus, it is possible that the effects observed here are tapping the variance shared between WM and IQ. Further research is needed to determine the nature of this variance.
|
study
| 99.94 |
The other primary result in the Van Dyke et al. (2014) study was to emphasize the quality of linguistic representations, as measured by an assessment of receptive vocabulary, as a factor in determining retrieval success. On the basis of this, we hypothesized that verbal knowledge (as assessed by WAIS vocabulary) may be related to either syntactic or semantic interference or both. We found some evidence for such a claim, as we found that vocabulary did interact with semantic interference, though only in questioning answering and with an effect in the opposite direction to that expected (i.e., higher vocabulary subjects showed greater interference). We nevertheless interpret the significant result as supporting the suggestion that qualitative aspects of the to-be-retrieved representations contribute to the size of interference effects. Additionally, a role for another general ability measure related to interference resolution ability (i.e., the Stroop effect) might have been expected on the cue-based parsing approach, but this failed to interact with interference in any dependent measure. This is discussed further below.
|
study
| 100.0 |
An issue for all models is that, as shown in Table 8, the interactions between syntactic interference and capacity measures only appeared during sentence reading, whereas those for semantic interference only appeared during question answering. The failure to find an interaction between semantic interference and any individual differences measure during online processing is somewhat surprising given that a significant 47 ms semantic interference effect was obtained in the spillover region; however, this null interaction with individual differences measures was also reported in an earlier study (Van Dyke et al., 2014). The significant interaction in question answering RT between category probe and semantic interference might be taken to imply that semantic STM or WM capacity only comes into play in offline semantic processing (e.g., in reviewing the sentence interpretation before answering a question). However, it is possible that the question answering effects reflect online processes that were begun earlier, but were not complete until past the end of the sentence. This is plausible given that the integration of semantic information appears to be slower than that for syntactic information (McElree and Griffith, 1995, 1998; Boland and Blodgett, 2001; Friederici, 2002; Hagoort, 2003). The difference in time course could be due to the finite set of grammatical features to be considered vs. the more complex considerations involved in determining semantic fit (e.g., “the play arrives” may be plausible even though “play” is inanimate). In addition, an important point to note for the present paradigm is that the correct resolution of semantic interference depends on using discriminative syntactic cues. That is, further consideration of semantic features will not resolve the semantic interference between two nouns if both are equally plausible as the subject of the verb. Therefore, perhaps the later time course for semantic interaction effects occurs because semantic conflict attracts attention to semantic features, whereas resolution of the conflict involves a shift of attention to syntactic features6.
|
study
| 100.0 |
As discussed in the introduction, early studies relating complex span measures like reading span to sentence processing assumed that these measures reflected a single capacity that could be flexibly allocated to storage or processing (Daneman and Carpenter, 1980; Just and Carpenter, 1992). However, recent studies argue against the assumption that WM capacity reflects a unitary capacity. Both Shipstead et al. (2014) and Unsworth et al. (2014) concluded, on the basis of large scale individual differences studies, that WM capacity can be divided into three components reflecting primary memory capacity (i.e., the capacity for maintaining information in the focus of attention), attentional control, and the ability to retrieve information from outside the focus of attention (i.e., from secondary memory). Secondary memory retrieval ability was not assessed in the present study and thus we cannot comment on its potential contribution to interactions of WM capacity with sensitivity to syntactic and semantic interference. Although, digit span may not be an ideal measure of primary memory capacity, it is highly correlated with other measures that have been argued to reflect this capacity (e.g., running span; Cowan et al., 2005). Thus, the significant interaction of WM capacity with syntactic interference even with digit span in the model suggests that the influence of WM capacity does not reflect the influence of primary memory capacity. An obvious candidate for explaining the relevant shared variance between WM capacity and interference resolution that would be consistent within the cue-based retrieval framework is attentional control. This hypothesis could also explain the link observed between WM capacity as measured by the complex WM tasks and the efficiency of controlled memory retrieval in previous memory studies (Öztekin and McElree, 2010; Mızrak and Öztekin, 2016). Öztekin and McElree found that low-WM span subjects took longer for the controlled retrieval of episodic information as compared to high-WM span subjects. As they suggested that there should be no differences in subjects' primary memory capacity (or the limit of focus of attention) assuming both groups could only maintain 1-item, such a relation might reflect better attentional control for high WM span subjects.
|
study
| 99.94 |
However, no interactions with our measure most related to attentional control—Stroop interference—were observed in the current study. It is possible, though, that the Stroop effect is not the most appropriate measure of this capacity. Of note is the fact that in the Shipstead et al. (2014) study the Stroop effect had the lowest weight on the attentional control factor out of the three variables used to tap that construct (the other two being anti-saccade and flanker tests). Particularly for sentence parsing, the type of inhibition required for Stroop (inhibition of a prepotent response) may not be the same as the inhibition required to resolve interference from incorrectly retrieved information during sentence processing (see Friedman and Miyake, 2004). This may be more consistent with either a mechanism supporting selection from a range of partially matching competitors (e.g., Thompson-Schill et al., 1997; Novick et al., 2005), or reanalysis, involving rejection of an incorrectly retrieved item or incorrectly constructed dependency (Van Dyke and Lewis, 2003). In neither of these cases is there a prepotent response, and so it is perhaps not surprising that we failed to find this association with the Stroop effect. Clearly, however, future work would be needed to show that other measures of interference resolution ability, particularly those involved in the resolution of proactive interference (Friedman and Miyake, 2004; Pettigrew and Martin, 2014), do relate to syntactic and semantic interference effects. Ideally, such a study would also include measures of primary memory capacity and the ability to retrieve information from secondary memory, as cue-based retrieval from outside the focus of attention is a crucial component of the cue-based parsing approach. Thus, a finding that general secondary memory retrieval abilities are related to the resolution of interference in sentence processing would also be supportive of this view.
|
study
| 100.0 |
The relation of category probe span, a STM measure, to semantic interference may suggest that differences in aspects of primary memory do affect interference resolution in a code-specific manner. This result is consistent with finding in the WM literature indicating a role for modality-specific retention abilities, in addition to general WM capacity, in a variety of cognitive domains (See Conway and Kovacs, 2013). As the cue-based parsing approach has argued that primary memory has a capacity fixed to 1–2 items in the current focus of attention (e.g., Lewis et al., 2006), the findings for category probe were not predicted from this theoretical approach. However, within the cue-based parsing framework, this finding could be interpreted as reflecting individual differences in the rate at which semantic features may be reactivated or become lost outside the focus of attention. Moreover, the fact that this measure does not interact with syntactic interference may imply that the rate of feature loss is different for semantic and syntactic information. This view is equivalent to the assumption in the multiple capacities approach of different capacities for semantic and syntactic information—framing it instead in terms of the rate of feature loss instead of buffer capacity (Martin and Romani, 1994; Martin and He, 2004). Thus, we might expect that a separate measure of syntactic retention—if such could be identified—would relate to syntactic interference, with the size of the syntactic interference effect being determined by the rate at which syntactic features are reactivated or lost.
|
study
| 99.94 |
In line with prior studies, our study demonstrated semantic and syntactic interference from unavailable constituents during sentence processing, consistent with the cue-based parsing approach. The novel aspect of the present study was the investigation of the role of individual differences in WM in modulating these interference effects. We found that general WM capacity derived from complex span tasks showed a relation to syntactic interference during online sentence processing, and to semantic interference during question answering. In addition, a measure of semantic STM capacity predicted the size of semantic but not syntactic interference effects in question answering, while phonological capacity did not predict the size of any interference effects. These interactions with WM were observed in both online and offline processing, even when controlling for vocabulary differences.
|
study
| 100.0 |
The pattern of results argues against claims that a specialized WM is involved in sentence parsing that is different from the capacities tapped by standard simple or complex span measures (Caplan and Waters, 1999). We speculate that the relations to general WM capacity reflect the role controlled attention and potentially secondary memory retrieval involved in both complex span measures and in resolving interference during sentence comprehension. In addition, we consider the specific relation between semantic STM and semantic interference as an indication that code-specific retention capacities mediate resolution and that the rate of loss of semantic or syntactic features (if such could be measured) may differ separately across individuals. This latter assumption is consistent with the multiple capacities approach to WM in which there are separable syntactic and semantic capacities, with the rate of loss of featural information replacing the notion of capacity limits.
|
study
| 100.0 |
There are limitations to the current study, which could be addressed by future research. Most of these were mentioned earlier, but will be summarized here. First, the multiple capacities approach assumes a separable syntactic capacity, but no specific measure of that capacity was included here. In future work, it would be important to include a measure of the ability to retain syntactic information per se, which would have to be demonstrated to be separable from semantic retention and general working memory capacity. Second, with respect to the cue-based parsing approach, despite the proposal that WM capacity may be so limited as to be irrelevant for parsing, we did nevertheless observe significant relationships between our measure of general WM capacity and comprehension. In the face of data pointing to a highly limited WM capacity for sentence processing (e.g., McElree et al., 2003; Johns et al., 2015), future research will need to address the question of what these measures represent, if not capacity. We have noted that recent research with WM capacity as measured by complex span tasks has suggested that separate mechanisms of maintenance in primary memory (which seems equivalent to the focus of attention), attentional control, and retrieval from long-term memory (e.g., Shipstead et al., 2014; Unsworth et al., 2014) underlie this construct. Future work will need to sort out which of these is the source of the relation between general WM and sentence processing observed here. Here we suggested that attentional control may underlie our findings, but did not measure this capacity directly. This would be important to do. In particular, it will be important to test whether effects of WM capacity would disappear when a measure of the ability to resolve proactive interference (which is distinct from the ability to resolve response/distractor interference as in Stroop; Friedman and Miyake, 2004) is modeled. Finally, given the differences between some of the results obtained here and those reported elsewhere (such as the influence of vocabulary on the direction of interference effects), future work will be needed to understand the extent to which the relationship between WM, vocabulary, and interference resolution depends on the type of task (dual-task vs. standard reading) or the location of distractors (sentence-internal vs. sentence-external).
|
study
| 99.94 |
This study was carried out in accordance with the recommendations of the Rice University Institutional Review Board with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the Rice University Institutional Review Board.
|
other
| 99.94 |
Conception or design of the work: YT, RM, and JV. Data collection: YT. Data analysis and interpretation: YT, RM, and JV. Drafting the article: YT and RM. Critical revision of the article: YT, RM, and JV. Final approval of the version to be published: YT, RM, and JV.
|
other
| 99.94 |
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer CH and the handling Editor declared their shared affiliation, and the handling Editor states that the process nevertheless met the standards of a fair and objective review.
|
other
| 99.94 |
Plants as sessile organisms cannot escape from negative effects imposed by detrimental environments such as high salinity, drought, freezing, high temperature, and flooding. Soil salinity has increasingly become one of major abiotic stresses that constraint plant growth worldwide (Frommer et al., 1999). In nature, soil salinity and alkalinity often occurs simultaneously due to the complexity of soils (Zhang et al., 2015). Approximately half of the saline soils in earth’s crust contain NaHCO3 and Na2CO3, which are the main factors that contribute to soil alkalinity (Yang et al., 2009). Excess Na+ and high pH value in saline–alkaline soils cause considerable damages to plant growth and development, whereas most plant species are more susceptible to high pH soils (more than 8.0) than saline soils (Tang et al., 2014; Li et al., 2016). High soil pH adversely affects seed germination, root cell structure and functions, the availability and absorption of nutrient elements, thereby leading to a remarkable decrease in crop yield and quality (Tang et al., 2014; Zhou et al., 2016a). According to the statistics, there is more than 800 million hectare of saline–alkaline soils in the world (Martinez-Beltran and Manzur, 2005). Hence, it is an urgent need to develop effective strategies to enhance the ability of plants to tolerate saline–alkaline conditions.
|
review
| 99.3 |
Saline–alkaline soils are generally characterized by high pH value and Na+ toxicity (Abadía et al., 2011; Tang et al., 2014; Li et al., 2016). High pH value decreases the solubility of soil iron (Fe), and most of Fe occurs in the insoluble form of Fe3+, which is not easily absorbed by plants (Romera and Alcántara, 2004). Upon exposure to alkaline stress, plants often exhibit typical symptoms of Fe deficiency-induced chlorosis (Gong et al., 2014; Zhou et al., 2016a). Emerging evidence has indicated that the enhanced Fe acquisition can confer greater tolerance of plants to alkaline stress (Li et al., 2016; Zhou et al., 2016a). During long-term evolution, different plant species develop strategy I and II mechanisms to adapt to Fe deficient conditions, respectively (Marschner and Römheld, 1994). Strategy I plants including dicot and non-graminaceous monocot species acquire Fe mainly by three processes including rhizospheric acidification (plasma membrane-localized H+-ATPase, AHA2; Santi and Schmidt, 2009), Fe3+ reduction (ferric chelate reductase, FRO2; Robinson et al., 1999), and Fe2+ transport (iron-regulated high-affinity transporter, IRT1; Varotto et al., 2002). Furthermore, Fe can go through long-distance transport from roots to shoots by several crucial genes such as FRD3 (Green and Rogers, 2004), NAS (Haydon and Cobbett, 2007), and YSL (Waters et al., 2006). Strategy II plants including graminaceous species acquire Fe by root secretion of the mugineic acid (MA) family of phytosiderophores (PCs) to chelate Fe3+ (Jolley and Brown, 1989). Compared with strategy I plants, the strategy II plants exhibit better growth performance under alkaline stress, since the PCs-dependent Fe uptake is less susceptible to high pH conditions (Römheld and Marschner, 1986; Nozoye et al., 2011). However, the protons released by the strategy I plants are largely buffered by alkaline stress, and thus reducing the availability of soil Fe (Ohwaki and Sugahara, 1997). Importantly, exogenous abscisic acid (ABA) remarkably mitigates Fe deficiency-induced leaf chlorosis in plants by enhancing translocation of Fe from roots to shoots, indicating that high ABA levels may be beneficial to improve alkaline tolerance in plants by regulating Fe translocation (Lei et al., 2014).
|
review
| 98.94 |
Besides low availability of Fe, plants experiencing saline–alkaline stress resulting from high Na+ concentrations encounter problems such as osmotic imbalance and ion toxicity (Yang et al., 2007; Wang et al., 2012). Na+ toxicity is often associated with the systemic dysfunctions of uptake and distribution of K+ in plants (Shabala and Cuin, 2008; Anschütz et al., 2014). Numerous studies have indicated that saline-tolerant plants can effectively control intracellular K+ and Na+ balance, which is required for the stability of membrane potential and enzymatic activities (Anschütz et al., 2014; Zhang et al., 2016). The cytosol of saline-tolerant plants can maintain high K+ and low Na+ under salt stress. Recently, ABA has been shown to regulate the expression of tonoplast Na+/H+ antiporter genes, thereby modulating K+ and Na+ homeostasis (Fukuda et al., 2011).
|
study
| 96.6 |
Importantly, nitric oxide (NO) serves as a secondary messenger of ABA to enhance salt tolerance by increasing the K+/Na+ ratio (León et al., 2014). It has been indicated that plants seem to own the priming-like mechanisms that memorize the foregoing NO exposure events and activate defensive responses following harmful conditions (Tanou et al., 2009). Zhang et al. (2009) have reported that transgenic tobacco plants with high ABA levels are more tolerant to the controls under salt stress, which is closely associated with the ABA-induced NO accumulation. NO exposure markedly increases the tolerance of plants to Fe deficient conditions by efficient mobilization of cell wall Fe and activation of Fe deficiency-induced transcription factor 1 (FIT1) that regulates Fe uptake in plants (Graziano and Lamattina, 2007; Chen et al., 2010; Wang et al., 2017). Thus, plants with high level of ABA may possess more efficient systems to acquire Fe and detoxify Na+ for resisting the saline–alkaline stress.
|
study
| 99.94 |
Recently, growing attention has been attracted to beneficial soil bacteria present in plant rhizosphere. These rhizosphere-inhabiting microbes are collectively referred to as plant growth promoting rhizobacteria (PGPR) that have been widely employed in modern agriculture (Yuan et al., 2013; Mishra et al., 2014; Zebelo et al., 2016). A large number of studies have shown that PGPR strains can interact with plants, and control plant growth and pathogen invasion by synthesizing some growth regulators such as polyamines, hormones, and antibiotic substances (Dey et al., 2004; Scholz et al., 2011; Zhou et al., 2016b). So far, many works have been made to enhance the adaptation of plants to various abiotic stresses such as drought and salt stress by application of PGPR (Ait Barka et al., 2006; Sukweenadhi et al., 2015; Zhou et al., 2016b). However, lack of researches exists on the information about PGPR-induced saline–alkaline tolerance in plants.
|
review
| 99.9 |
Chrysanthemum is the most economically important medicinal and ornamental plants worldwide. Chuju, a cultivar of Chrysanthemum morifolium, has been widely exploited for drink and medicinal applications, and is ranked the first among the four famous Chrysanthemum plants in China (Xie et al., 2012). However, saline–alkaline soils often lead to plant growth inhibition and yield loss. Here, the main aim of this study tried to increase the tolerance of Chrysanthemum plants to saline–alkaline conditions by application of PGPR. The inoculation of Chrysanthemum plants with Bacillus licheniformis SA03 displayed better growth performance under saline–alkaline stress compared with non-inoculated plants. Moreover, we explored the underlying mechanisms at the physiological and molecular levels responsible for SA03-induced stress tolerance of plants.
|
study
| 99.94 |
Seeds of C. morifolium cv. Chuju were surface sterilized in 0.1% (w/v) mercury dichloride (HgCl2), followed by rinsing at least three times with sterile water and placed on half-strength (1/2) MS medium containing 0.8% (w/v) agar and 1.5% (w/v) sucrose. The sterilized seeds were vernalized for 48 h at 4°C in darkness, and were then cultured in a growth chamber at 25°C with a photoperiod of 14 h light/10 h dark (light intensity of 200 μmol m-2 s-1). After 10 days (d) of germination, the seedlings were transferred into pots with soils (3:1:1, clay:vermiculite:perlite). Soils were sterilized by autoclaving at 120°C for 1 h before using it.
|
study
| 100.0 |
Bacillus licheniformis SA03 was isolated from the rhizospheric soils of Chrysanthemum plants grown under saline–alkaline conditions, and identified by 16S rDNA sequencing (GenBank No. KY828223). This bacteria strain was inoculated into MCF liquid medium (Freitas et al., 2015), and incubated in an orbital shaker (200 rpm) at 28°C for 18 h. Bacteria were collected by centrifugation at 8000 rpm at 4°C for 15 min and the centrifugal tubes were washed with 0.1 M phosphate-buffered saline (PBS, pH 7.2), and were then diluted to an OD570 nm absorbance of 0.7 in PBS buffer for microbial inoculation.
|
study
| 100.0 |
About 3-month-old Chrysanthemum plants were inoculated with 3 ml of PBS containing B. licheniformis SA03 or with 3 ml of PBS (as controls). After 10 days of co-culture, these plants were irrigated with sterile water containing 50 mM NaHCO3 and 50 mM Na2CO3 that allowed pH value of soils to reach approximate 8.2. After that, these plants were daily watered until plant tissues were harvested. Lastly, the harvested samples were used for various physiological and biochemical analyses.
|
study
| 99.94 |
To measure metal ion content, about 500 mg of shoots and roots were firstly separated from Chrysanthemum plants, respectively. Then, the dried samples were ground and digested with 15 ml nitric acid (HNO3)/perhydrol (H2O2) (3:1, v/v) in a microwave system (MARS, CEM) at 160°C for 20 min. After centrifugation at 12,000 rpm for 10 min, the supernatant was used for determining metal ion contents by inductively coupled plasma-atomic emission spectroscopy (ICP-AES, Thermo Scientific, Waltham, MA, United States) as described recently by Lei et al. (2014).
|
study
| 100.0 |
To examine total chlorophyll content in Chrysanthemum leaves, 500 mg of leaf samples was harvested and extracted with 5 ml of aqueous acetone (80%, v/v), and then centrifuged at 12,000 rpm for 15 min. Absorbance of the supernatant was recorded at wavelengths of 645 and 663 nm, respectively. The amounts of chlorophyll in leaves were calculated according to the formulae: 8.02 × A663 + 20.21 × A645 as reported previously by Porra (2002).
|
study
| 100.0 |
We further measured several chlorophyll fluorescence parameters including net photosynthetic rate (Pn), the effective quantum yield of PSII photochemistry (ΦPSII), and the ratio of the variable and the maximum chlorophyll fluorescence (Fv/Fm) according to the method described recently by Du et al. (2015).
|
study
| 99.94 |
The content of two major types of reactive oxygen species (ROS) including O2•– and H2O2 was measured according to the method described by Liu and Pang (2010). The values of MDA and EL were determined according to the method reported by Jiang and Zhang (2001). Moreover, the activities of antioxidant enzymes were assayed according to the methods reported by Mostofa et al. (2015).
|
study
| 100.0 |
Abscisic acid was firstly extracted and purified from shoots and roots, respectively. Then, the ABA content was determined by an indirect ELISA technique as described by Zhang et al. (2009). The NO content was measured according to the method described by Cvetkovska et al. (2014).
|
study
| 100.0 |
Total RNA was extracted from roots of the non-inoculated (NI) and inoculated (I) plants using Trizol reagent (Invitrogen, United States) following the manufacturer’s instructions. Residual DNA in total RNA was further digested by DNase (Invitrogen, United States). Then, the quality of integrity of RNA samples were analyzed using Agilent 2100 Bioanalyser (Agilent, United States). Total RNA from three independent plants in each group was used to construct two cDNA libraries in parallel using the Illumina TruSeqTM RNA-seq library prep kit (Illumina, United States) according to the method described by Sun et al. (2016). The two cDNA libraries were sequenced using the Hiseq 2500 platform (Illumina, United States). The sequencing raw data were processed by removing the low-quality reads, and then submitted into the NCBI database (SRA1).
|
study
| 100.0 |
Gene direction and functions were annotated based on the Nr annotations. Gene ontology (GO) annotations with the default parameters were analyzed by the Blast2GO program, which were clustered into three groups including biological process, cellular component, and molecular function. Furthermore, the identification of differentially expressed genes (DEGs) between the NI and I libraries was conducted using a rigorous algorithm at false discovery rate (FDR)-adjusted p-value < 0.05. GO term2 was assigned to DEGs based on the above GO annotations. In addition, GO enrichment analysis was performed to search significantly enriched functional classification.
|
study
| 100.0 |
Total RNA were extracted from roots using Trizol reagent (Invitrogen, United States), and genomic DNA contamination in RNA samples were digested by DNase (Promega, United States). Then, about 500 ng of total RNA was reversely transcribed into first-strand cDNA using a PrimeScript® RT Reagent kit (TaKaRa, Japan) following the manufacturer’s instructions. qRT-PCR reactions were performed in a ABI 7500 real-time PCR machine. Each reaction contained 10 μl of 2 × SYBR Green Master Mix reagents, 1 μl of cDNA samples, and 0.5 μl of 10 μM primers in a final volume of 20 μl. The reaction conditions were as follows: 95°C for 30 s, followed by 40 cycles of 95°C for 15 s, 60°C for 30 s, and 72°C for 30 s. The GAPDH gene was used as an internal control to normalize target gene expression. Each experiment was conducted in three biological replicates. Each biological replicate was run with three independent cDNA samples. Gene specific primers for IRT1, FRO2, FRD3, NHX1, NHX2, NHX5, AHA2, ZEP1, YSL1, YSL2, SAUR21, NAS1, and GAPDH were listed in Supplementary Table S1.
|
study
| 100.0 |
Leaf samples were separated and cut into 0.5 cm × 0.5 cm pieces, and then fixed with 2.5% glutaraldehyde for 12 h. After at least three rinses with 0.1 M PBS, the samples were fixed with 1.0% osmium tetroxide (OsO4) for 2 h, followed by three rinses with PBS. Subsequently, the samples were dehydrated in an acetone dilution series from 30 to 100%, embedded in Spurr’s resin (Ted Pella, United States), and cut into thin sections (70–90 nm). Lastly, these sections were observed by transmission electron microscopy at 80 kV. At least five dependent samples and more than 16 individual chloroplasts were observed for each treatment.
|
study
| 100.0 |
Data were analyzed using SAS statistical software (SAS Institute, Cary, NC, United States), and were represented as the mean values ± SE. Significant differences were analyzed by one-way or two-way ANOVA followed by the Duncan’s multiple range test at P < 0.05.
|
study
| 99.4 |
To examine the effects of SA03-inoculation on the growth of Chrysanthemum plants under saline–alkaline stress, about 3-month-old plants were inoculated with this bacteria strain. After 10 days of co-culture, the non-inoculated and inoculated plants were subjected to saline–alkaline treatment for 4 weeks. There was no significant difference between the non-inoculated and inoculated plants before saline–alkaline treatment. However, the non-inoculated plants exhibited curly and yellowing leaves under saline–alkaline stress, while leaf chlorosis was hardly observed in the inoculated plants (Figure 1A). Several physiological parameters including total leaf area (LA), fresh and dry weight of plants were further examined. Soil inoculation greatly elevated about two-fold total LA in plants under the stress compared with the non-inoculated plants [Figure 1B; F(3,36) = 164.60, P < 0.05]. The inoculation with SA03 also led to 45 and 32% increase of shoot and root fresh weight, respectively [Figure 1C; F(7,72) = 296.99, P < 0.05]. Similarly, dry weight was pronouncedly increased in the inoculated plants compared with the non-inoculated plants [Figure 1D; F(7,72) = 146.08, P < 0.05]. Survival rates of plants were calculated until 8 weeks after saline–alkaline treatment. Soil inoculation resulted in a great increase of survival rates in the stress-treated plants. The non-inoculated plants grown in saline–alkaline soils for 8 weeks did not survive, while the survival rates of inoculated plants were about 76% (Figure 1E).
|
study
| 100.0 |
Effects of B. licheniformis SA03 on Chrysanthemum plants under saline–alkaline stress. After 10 days of bacterial inoculation, the non-inoculated (NI) and inoculated (I) were subjected to saline–alkaline treatment for 4 weeks, respectively. The treated plants were used to analyze (A) growth phenotype, (B) total leaf areas (LA), (C) shoot and root fresh weight, (D) shoot and root dry weight, and (E) survival rate. BS, before the stress treatment; AS, after the stress treatment. Data are expressed as the mean values of three replicates (±SE) with 10 plants each. Different letters indicate significant differences using two-way ANOVA followed by the Duncan’s multiple range test at P < 0.05.
|
study
| 100.0 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.