Neural correlates of syntactic ambiguity in sentence comprehension for low and high span readers

Syntactically ambiguous sentences have been found to be difficult to process, in particular, for individuals with low working memory capacity. The current study used fMRI to investigate the neural basis of this effect in the processing of written sentences. Participants with high and low working memory capacity read sentences with either a short or long region of temporary syntactic ambiguity while being scanned. A distributed left-dominant network in the peri-sylvian region was identified to support sentence processing in the critical region of the sentence. Within this network, only the superior portion of Broca's area (BA 44) and a parietal region showed an activation increase as a function of the length of the syntactically ambiguous region in the sentence. Furthermore, it was only the BA 44 region that exhibited an interaction of working memory span, length of the syntactic ambiguity, and sentence complexity. In this area, the activation increase for syntactically more complex sentences became only significant under longer regions of ambiguity, and for low span readers only. This finding suggests that neural activity in BA 44 increases during sentence comprehension when processing demands increase, be it due to syntactic processing demands or by an interaction with the individually available working memory capacity

Bilingual access of homonym meanings : individual differences in bilingual access of homonym meanings

The goal of the present study was to identify the cognitive processes that underlie lexical ambiguity resolution in a second language (L2). We examined which cognitive factors predict the efficiency in accessing subordinate meanings of L2 homonyms in a sample of highly-proficient, Spanish–English bilinguals. The predictive ability of individual differences in (1) homonym processing in the L1, (2) working memory capacity and (3) sensitivity to cross-language form overlap were examined. In two experiments, participants were presented with cognate and noncognate homonyms as either a prime in a lexical decision task (Experiment 1) or embedded in a sentence (Experiment 2). In both experiments speed and accuracy in accessing subordinate meanings in the L1 was the strongest predictor of speed and accuracy in accessing subordinate meanings in the L2. Sensitivity to cross-language form overlap predicted performance in lexical decision while working memory capacity predicted processing in sentence comprehension

The role of verbal working memory in children's sentence comprehension: A critical review

This article reviews research that has investigated the role of verbal working memory (VWM) in sentence comprehension in both typical and atypical developmental populations. Two theoretical approaches that specify different roles for VWM in sentence comprehension are considered: (i) capacity-limit approaches, which treat VWM as a theoretical primitive that causally constrains language processing and acquisition, and (ii) the experience-based approach, which argues that VWM is an emergent property of long-term linguistic knowledge. The empirical literature relevant to these different approaches is then reviewed. Although there has been considerable recent research on the topic, it is concluded that the current role of working memory in sentence comprehension in development is unclear, calling for a greater number of controlled systematic developmental studies on the topic

Assessing Phonology, Syntax & Working Memory using ERP: Towards an Understanding of the Underlying Cause of Developmental Dyslexia

Event-related brain potentials (ERPs) were recorded from 20 children with dyslexia and controls matched on age, sex, nonverbal reasoning, and handedness (ages 8-12 years) as they listened to and read sentences that varied in syntactic complexity and the working memory load they induced [subject-subject (SS) and subject-object (SO) relative clause sentences]. In each modality, control children demonstrated amplitude differences between the brainwave potentials elicited to each sentence type. When listening, controls, and children with dyslexia did not differ in the N400 effect elicited in response to the relative verb of SO sentences, thus indicating auditory sentential processing occurred in a similar manner for both groups of children early in the sentences. However, by the later main verb region of SO sentences, thematic role assignment, as indexed by the left anterior negativity (LAN), was absent in children with dyslexia, suggested that rather than syntactic complexity, overtaxed working memory inhibited dyslexics’s ability to assign thematic roles. When reading, the N400 effect was again demonstrated by each group at the relative clause of SO sentences; however children with dyslexia exhibited a latency delay in comparison to control children. Similar to auditory processing at the main verb, while reading only the control goup demonstrated LAN effects in response to SO sentence structure. In order to investigate working memory capacity in more temporal detail, slow cortical potentials were measured over the full duration of the sentence. Results demonstrated that while both groups were able to utilize phonological working memory to store sentential information when listening to sentences, only controls could reliably do so when reading. The data indicates that the syntactic deficits inherent in dyslexia are mediated by phonological working memory. These results support the phonological limitation hypothesis posited by Shankweiler et al. (1992), which contends that all impediments related to dyslexia are mediated by a primary deficit in phonological processing

Non-incremental parsing strategies: the role of short-term working memory

Thesis (M.S.)--Boston UniversityThis study sought to investigate further the findings of Caplan et al. (2011) that heightened self-paced reading [SPR] times may cmrelate positively with comprehension measures at points of significantly increased processing load, indicating use of atypical non-incremental parsing methods. Reading comprehension tasks were presented in SPR and eye-tracking paradigms, and three measures of short-term working memory [ST- WM] were administered. Experimental stimuli consisted of early-closure and late-closure sentences, as the former require the reader to revise his or her initial parse of the sentence at a disambiguating word (creating a point of significantly increased processing load) while the latter do not. Independent variables included WM capacity and sentence type, and dependent variables included self-paced reading time [RT], comprehension accuracy, and five measures of eye fixations: first fixation duration, go past time, dwell time, regression out, and regression in. It was hypothesized that participants would show heightened RT correlating positively with comprehension accuracy at the disambiguating point of the early-closure sentences. It was further predicted that this would correspond with a heightened probability of regression out of the area at this same point. Finally, it was predicted that participants with higher ST-WM capacity would be more likely to show these effects, as they were more likely to use them successfully. No correlation between RT and accuracy was found in the SPR paradigm, and while participants did show heightened probability of regression out of the critical phrase in the early-closure than in the late closure sentences, this phenomenon was also present at nearly all other points in the sentence. A significant interaction between ST-WM capacity and sentence type on RT, such that participants with higher WM capacity showed supra-additively high RT at the critical point in early-closure sentences, was observed. This finding indicates that readers with higher ST-WM capacity may persist in processing sentences longer than their lower ST-WM capacity peers, as argued by Stine-Morrow, Ryan, and Leonard (2000)

Low-Frequency Oscillations Code Speech during Verbal Working Memory

Item does not contain fulltextThe way the human brain represents speech in memory is still unknown. An obvious characteristic of speech is its evolvement over time. During speech processing, neural oscillations are modulated by the temporal properties of the acoustic speech signal, but also acquired knowledge on the temporal structure of language influences speech perception-related brain activity. This suggests that speech could be represented in the temporal domain, a form of representation that the brain also uses to encode autobiographic memories. Empirical evidence for such a memory code is lacking. We investigated the nature of speech memory representations using direct cortical recordings in the left perisylvian cortex during delayed sentence reproduction in female and male patients undergoing awake tumor surgery. Our results reveal that the brain endogenously represents speech in the temporal domain. Temporal pattern similarity analyses revealed that the phase of frontotemporal low-frequency oscillations, primarily in the beta range, represents sentence identity in working memory. The positive relationship between beta power during working memory and task performance suggests that working memory representations benefit from increased phase separation.SIGNIFICANCE STATEMENT Memory is an endogenous source of information based on experience. While neural oscillations encode autobiographic memories in the temporal domain, little is known on their contribution to memory representations of human speech. Our electrocortical recordings in participants who maintain sentences in memory identify the phase of left frontotemporal beta oscillations as the most prominent information carrier of sentence identity. These observations provide evidence for a theoretical model on speech memory representations and explain why interfering with beta oscillations in the left inferior frontal cortex diminishes verbal working memory capacity. The lack of sentence identity coding at the syllabic rate suggests that sentences are represented in memory in a more abstract form compared with speech coding during speech perception and production