Abstract
Successful sentence comprehension often requires the ability to link non-adjacent constituents. Recent studies implicate that readers link non-adjacent constituents through an associative, direct-access mechanism, while working memory (WM) or short-term memory (STM) may not play an important role in this operation because only 1- 2 items could be maintained in the focus of attention (Van Dyke, 2007). However, prior studies with aphasic patients have supported a role for semantic STM and executive control in sentence processing (Martin et al., 2004; Vuong et al., 2011). Recently, a study with healthy subjects also demonstrated a role for semantic STM in resolving semantic interference, and a role for attentional control in resolving syntactic interference during sentence comprehension (Tan et al., 2011). These results suggested that semantic STM and attentional control are involved in semantic and syntactic aspects of sentence processing, respectively. This study further examined semantic and syntactic interference resolution in aphasic patients, who show dramatic variation in their WM/STM capacities. Semantic and syntactic interference were manipulated in a 2 x 2 design by varying the semantic plausibility of the intervening noun as the subject of the main verb and varying the syntactic role of the intervening noun (subj vs. obj). Both manipulations have been shown to increase difficulty in linking the head noun to the main verb. Example: Low-Syn: The student who was tired of the demanding assignment/coach yesterday was leaving. High-Syn: The student who said that the assignment/coach was demanding yesterday was leaving. Ten aphasic patients with good single word comprehension abilities but deficits on STM tasks were assessed on whole sentence RTs and on time and accuracy to answer comprehension questions (e.g. Was the student leaving?“). Interference effects were calculated by computing difference scores for RT and accuracy for low vs. high interference conditions. For RTs, the semantic and syntactic interference effects for most patients were within the range of controls. However, most of the patients showed exaggerated sensitivity to either semantic or syntactic interference for comprehension questions accuracy. Moreover, patients with relative better semantic STM made fewer errors in semantic interference resolution (r = -.77, p = .04), while patient with better attentional control made fewer errors in syntactic interference resolution (r = -.93, p < .001). However, neither phonological STM nor vocabulary was related to sentence processing. Our current results are consistent with the previous findings that WM and attentional control are critical for sentence processing. Poor maintenance of semantic information and deficits in attentional control lead to difficulties in semantic and syntactic processing. Reference Martin, R. C., & He, T. (2004). Semantic STM and its role in sentence processing: A replication. Brain & Lang, 89, 76-82. Tan, Y., Martin, R.C., & Van Dyke, J.A. (2011). Interference and WM in sentence comprehension. CUNY, Palo Alto, CA. Van Dyke, J.A. (2007). Interference effects from grammatically unavailable constituents during sentence processing. JEP:LMC, 33, 407-430. Vuong, L. C., & Martin, R. C. (2011). LIFG-based attentional control and the resolution of lexical ambiguities in sentence context. Brain & Lang, 116, 22-32.
