The neuropsychology of sentence processing: Where do we stand?

Extra-Linguistic Cognitive Functions Involved in the Token Test: Results from a Cohort of Non-Aphasic Stroke Patients with Right Hemisphere Lesion

BACKGROUND

The Token Test (TT) is widely used to examine comprehension disorders in aphasic patients, but abilities other than language may affect a patient's performance. This study aims to explore the correlation between the TT subtest performances and the performances in extra-linguistic cognitive areas in a cohort of patients from the Intensive Rehabilitation Post-Stroke (RIPS) study with a first, right hemisphere stroke and without aphasia, prospectively enrolled at admission to intensive inpatient post-acute rehabilitation.

METHODS

The patients were administered the TT (50-item version), the forward and backward digit span (DST), and the Montreal Cognitive Assessment (MoCA). Spearman's partial correlations adjusted by age were used to evaluate the association between the number of errors in the TT and the other tests' corrected scores.

RESULTS

Of the 37 patients enrolled in this study, 29.7% made 3-11 errors on the TT, 27.0% more than 11 errors, mostly in parts IV and V. The forward and backward digit span scores showed correlations with errors in part V of the TT (r = -0.408, p = 0.013; r = -0.307, p = 0.027). The errors in part IV of the TT presented a correlation with a forward digit span too (r = -0.394, p = 0.017). With respect to MoCA domains, executive functioning, and orientation were related to the TT part V errors (r = -0.468, p = 0.007; r = -0.499, p = 0.003). The orientation also correlated with the TT part III (r = -0.504, p = 0.002).

CONCLUSION

Our findings show that the TT performances in patients with right hemisphere stroke and without aphasia are related to impairments in auditory-verbal span/auditory working memory mostly for TT scores on subpart V as measured by the DST and to executive function and orientation, as measured by the MoCA subtests.

Rapid Serial Visual Presentation Interacts with Ambiguity During Sentence Comprehension

Conventional opinion about using Rapid Serial Visual Presentation (RSVP) for examining sentence comprehension maintains that RSVP taxes working memory (WM), which probably affects sentence processing. However, most RSVP studies only infer the involvement of WM. Other cognitive resources, such as cognitive control or vocabulary may also impact sentence comprehension and interact with RSVP. Further, sentence ambiguity is predicted to interact with RSVP and cognitive resources to impact sentence comprehension. To test these relationships, participants read ambiguous and unambiguous sentences using RSVP and Whole-Sentence presentation, followed by comprehension questions that were targeted to the ambiguous region of the sentences. Presentation type and ambiguity interacted to affect RT such that the effect of RSVP was exaggerated for ambiguous sentences. RT effects were moderated by WM and vocabulary. WM and cognitive control affected accuracy. Findings are discussed in light of depth of processing and the impact of cognitive resources on sentence comprehension.

The role of executive control in resolving grammatical number conflict in sentence comprehension

In sentences with a complex subject noun phrase, like "The key to the cabinets is lost", the grammatical number of the head noun (key) may be the same or different from that of the modifier noun phrase (cabinets). When the number is the same, comprehension is usually easier than when it is different. Grammatical number computation may occur while processing the modifier noun (integration phase) or while processing the verb (checking phase). We investigated at which phase number conflict and plausibility of the modifier noun as subject for the verb affect processing, and we imposed a gaze-contingent tone discrimination task in either phase to test whether number computation involves executive control. At both phases, gaze durations were longer when a concurrent tone task was present. Additionally, at the integration phase, gaze durations were longer under number conflict, and this effect was enhanced by the presence of a tone task, whereas no effects of plausibility of the modifier were observed. The finding that the effect of number match was larger under load shows that computation of the grammatical number of the complex noun phrase requires executive control in the integration phase, but not in the checking phase.

Executive Function and Ambiguous Sentence Comprehension

PURPOSE

Sentence comprehension is a critical skill in today's literate society. Recent evidence suggests that processing and comprehending language taps cognitive as well as linguistic abilities, a finding that has critical import for clinicians who have clients with language disorders. To promote awareness of the impact of cognition, especially executive function (EF) and working memory (WM), this opinion article presents current views of how sentences are processed and links the various steps of the process to specific EF and WM subcomponents.

METHOD

The article focuses on ambiguous sentences, pointing out the similar types of processing needed when resolving an ambiguity and performing EF tasks.

RESULTS

We discuss the potential overlap between the neurobiology of sentence processing and EF and the evidence supporting a link between EF and sentence processes.

CONCLUSION

Awareness of the potential role of EF and WM in sentence comprehension will help clinicians be more aware of potential cognitive-linguistic deficits in their clients. Future research will help to clarify the link between EF and sentence comprehension.

The language faculty that wasn't: a usage-based account of natural language recursion

In the generative tradition, the language faculty has been shrinking—perhaps to include only the mechanism of recursion. This paper argues that even this view of the language faculty is too expansive. We first argue that a language faculty is difficult to reconcile with evolutionary considerations. We then focus on recursion as a detailed case study, arguing that our ability to process recursive structure does not rely on recursion as a property of the grammar, but instead emerges gradually by piggybacking on domain-general sequence learning abilities. Evidence from genetics, comparative work on non-human primates, and cognitive neuroscience suggests that humans have evolved complex sequence learning skills, which were subsequently pressed into service to accommodate language. Constraints on sequence learning therefore have played an important role in shaping the cultural evolution of linguistic structure, including our limited abilities for processing recursive structure. Finally, we re-evaluate some of the key considerations that have often been taken to require the postulation of a language faculty.

The language faculty that wasn't: a usage-based account of natural language recursion

In the generative tradition, the language faculty has been shrinking-perhaps to include only the mechanism of recursion. This paper argues that even this view of the language faculty is too expansive. We first argue that a language faculty is difficult to reconcile with evolutionary considerations. We then focus on recursion as a detailed case study, arguing that our ability to process recursive structure does not rely on recursion as a property of the grammar, but instead emerges gradually by piggybacking on domain-general sequence learning abilities. Evidence from genetics, comparative work on non-human primates, and cognitive neuroscience suggests that humans have evolved complex sequence learning skills, which were subsequently pressed into service to accommodate language. Constraints on sequence learning therefore have played an important role in shaping the cultural evolution of linguistic structure, including our limited abilities for processing recursive structure. Finally, we re-evaluate some of the key considerations that have often been taken to require the postulation of a language faculty.

A Computational Evaluation of Sentence Processing Deficits in Aphasia

Individuals with agrammatic Broca's aphasia experience difficulty when processing reversible non-canonical sentences. Different accounts have been proposed to explain this phenomenon. The Trace Deletion account (Grodzinsky, 1995, 2000, 2006) attributes this deficit to an impairment in syntactic representations, whereas others (e.g., Caplan, Waters, Dede, Michaud, & Reddy, 2007; Haarmann, Just, & Carpenter, 1997) propose that the underlying structural representations are unimpaired, but sentence comprehension is affected by processing deficits, such as slow lexical activation, reduction in memory resources, slowed processing and/or intermittent deficiency, among others. We test the claims of two processing accounts, slowed processing and intermittent deficiency, and two versions of the Trace Deletion Hypothesis (TDH), in a computational framework for sentence processing (Lewis & Vasishth, 2005) implemented in ACT-R (Anderson, Byrne, Douglass, Lebiere, & Qin, 2004). The assumption of slowed processing is operationalized as slow procedural memory, so that each processing action is performed slower than normal, and intermittent deficiency as extra noise in the procedural memory, so that the parsing steps are more noisy than normal. We operationalize the TDH as an absence of trace information in the parse tree. To test the predictions of the models implementing these theories, we use the data from a German sentence-picture matching study reported in Hanne, Sekerina, Vasishth, Burchert, and De Bleser (2011). The data consist of offline (sentence-picture matching accuracies and response times) and online (eye fixation proportions) measures. From among the models considered, the model assuming that both slowed processing and intermittent deficiency are present emerges as the best model of sentence processing difficulty in aphasia. The modeling of individual differences suggests that, if we assume that patients have both slowed processing and intermittent deficiency, they have them in differing degrees.

Preservation of passive constructions in a patient with primary progressive aphasia

Research into agrammatic comprehension in English has described a pattern of impaired understanding of passives and retained ability on active constructions. Some accounts of this dissociation predict that patients who are unable to comprehend actives will also be impaired in the comprehension of passives. We report the case of a man with primary progressive aphasia (PPA) (WR), whose comprehension was at chance on active sentences, but at ceiling on passives. In a series of reversible sentence comprehension tests WR displayed difficulties with active transitives and truncated actives with an auxiliary. In passive sentences, he displayed sensitivity to the agent marker by, as well as the passive morphology of the verb. This pattern of dissociation challenges current theories of agrammatic comprehension. We explore explanations based on the distinction between morphological and configurational cues, as well as on the semantic and discourse related differences between active and passive constructions.

A case for the involvement of phonological loop in sentence comprehension

The specific role of the phonological loop in sentence comprehension is still a matter of debate. We tested the behavioural consequences of activity disruption in left BA40 and BA44, key regions of the phonological loop, on language comprehension using 1Hz rTMS. Comprehension was assessed by means of two tasks: a sentence-to-picture matching task, with sentences varying in length and syntactic complexity (Experiment 1), and a sentence verification task (Experiment 2). rTMS over left BA40 significantly reduced accuracy for syntactically complex sentences and long, but syntactically simpler sentences, while rTMS over left BA44 significantly reduced accuracy only for syntactically complex sentences. rTMS applied over left BA40 also impaired performance on sentences in which word order was crucial. We suggest that the neural correlates of the phonological loop, left BA40 and BA44, are both involved in the comprehension of syntactically complex sentences, while only left BA40, corresponding to the short-term store, is recruited for the comprehension of long but syntactically simple sentences. Therefore, in contrast with the dominant view, we showed that sentence comprehension is a function of the phonological loop.

Working memory involvement in stuttering: exploring the evidence and research implications

Several studies of utterance planning and attention processes in stuttering have raised the prospect of working memory involvement in the disorder. In this paper, potential connections between stuttering and two elements of Baddeley's [Baddeley, A. D. (2003). Working memory: Looking back and looking forward. Neuroscience, 4, 829-839] working memory model, phonological memory and central executive, are posited. Empirical evidence is drawn from studies on phonological memory and dual-task performance among children and adults who stutter to examine support for the posited connections. Implications for research to examine working memory as one of the psycholinguistic bases of stuttering are presented.

EDUCATIONAL OBJECTIVES

The reader will learn about and be able to: (1) appraise potential relationships between working memory and stuttering; (2) evaluate empirical evidence that suggests the possibility of working memory involvement in stuttering; and (3) identify research directions to explore the role of working memory in stuttering.

What is the relationship between phonological short-term memory and speech processing?

Traditionally, models of speech comprehension and production do not depend on concepts and processes from the phonological short-term memory (pSTM) literature. Likewise, in working memory research, pSTM is considered to be a language-independent system that facilitates language acquisition rather than speech processing per se. We discuss couplings between pSTM, speech perception and speech production, and we propose that pSTM arises from the cycling of information between two phonological buffers, one involved in speech perception and one in speech production. We discuss the specific role of these processes in speech processing, and argue that models of speech perception and production, and our understanding of their neural bases, will benefit from incorporating them.