The resolution and recovery of filler-gap dependencies in aphasia: evidence from on-line anomaly detection

Sentence Recall in Latent and Anomic Aphasia: An Exploratory Study of Semantics and Syntax

We investigated whether semantic plausibility and syntactic complexity affect immediate sentence recall in people with latent and anomic aphasia. To date, these factors have not been explored in these types of aphasia. As with previous studies of sentence recall, we measured accuracy of verbatim recall and uniquely real-time speech measures. The results showed that accuracy did not distinguish performance between latent aphasia and neurotypical controls. However, some of the real-time speech measures distinguished performance between people with latent aphasia and neurotypical controls. There was some evidence, though not pervasive, that semantic plausibility and syntactic complexity influenced recall performance. There were no interactions between semantic plausibility and syntactic complexity. The speed of preparation of responses was slower in latent aphasia than controls; it was also slower in anomic aphasia than both latent and control groups. It appears that processing speed as indexed by temporal speech measures may be differentially compromised in latent and anomic aphasia. However, semantic plausibility and syntactic complexity did not show clear patterns of performance among the groups. Notwithstanding the absence of interactions, we advance an explanation based on conceptual short-term memory as to why semantically implausible sentences are typically more erroneous and possibly also slower in recall.

Thematic Integration Impairments in Primary Progressive Aphasia: Evidence From Eye-Tracking

Primary progressive aphasia (PPA) is a degenerative disease affecting language while leaving other cognitive facilities relatively unscathed. The agrammatic subtype of PPA (PPA-G) is characterized by agrammatic language production with impaired comprehension of noncanonical filler-gap syntactic structures, such as object-relatives [e.g., The sandwich that the girl ate (gap) was tasty], in which the filler (the sandwich) is displaced from the object position within the relative clause to a position preceding both the verb and the agent (the girl) and is replaced by a gap linked with the filler. One hypothesis suggests that the observed deficits of these structures reflect impaired thematic integration, including impaired prediction of the thematic role of the filler and impaired thematic integration at the gap, but spared structure building (i.e., creation of the gap). In the current study, we examined the on-line comprehension of object-relative and subject-relative clauses in healthy controls and individuals with agrammatic and logopenic PPA using eye-tracking. Eye-movement patterns in canonical subject-relative clause structures were essentially spared in both PPA groups. In contrast, eye-movement patterns in noncanonical object-relative clauses revealed delayed thematic prediction in both agrammatic and logopenic PPA, on-time structure building (i.e., gap-filling) in both groups, and abnormal thematic integration in agrammatic, but not logopenic, PPA. We argue that these results are consistent with the hypothesis that agrammatic comprehension deficits reflect impaired thematic integration.

Neural Connectivity in Syntactic Movement Processing

Linguistic theory suggests non-canonical sentences subvert the dominant agent-verb-theme order in English via displacement of sentence constituents to argument (NP-movement) or non-argument positions (wh-movement). Both processes have been associated with the left inferior frontal gyrus and posterior superior temporal gyrus, but differences in neural activity and connectivity between movement types have not been investigated. In the current study, functional magnetic resonance imaging data were acquired from 21 adult participants during an auditory sentence-picture verification task using passive and active sentences contrasted to isolate NP-movement, and object- and subject-cleft sentences contrasted to isolate wh-movement. Then, functional magnetic resonance imaging data from regions common to both movement types were entered into a dynamic causal modeling analysis to examine effective connectivity for wh-movement and NP-movement. Results showed greater left inferior frontal gyrus activation for Wh > NP-movement, but no activation for NP > Wh-movement. Both types of movement elicited activity in the opercular part of the left inferior frontal gyrus, left posterior superior temporal gyrus, and left medial superior frontal gyrus. The dynamic causal modeling analyses indicated that neither movement type significantly modulated the connection from the left inferior frontal gyrus to the left posterior superior temporal gyrus, nor vice-versa, suggesting no connectivity differences between wh- and NP-movement. These findings support the idea that increased complexity of wh-structures, compared to sentences with NP-movement, requires greater engagement of cognitive resources via increased neural activity in the left inferior frontal gyrus, but both movement types engage similar neural networks.

Recovery of Online Sentence Processing in Aphasia: Eye Movement Changes Resulting From Treatment of Underlying Forms

Purpose

The present study tested whether (and how) language treatment changed online sentence processing in individuals with aphasia.

Method

Participants with aphasia (n = 10) received a 12-week program of Treatment of Underlying Forms (Thompson & Shapiro, 2005) focused on production and comprehension of passive sentences. Before and after treatment, participants performed a sentence-picture matching task with active and passive sentences as eye movements were tracked. Twelve age-matched controls also performed the task once each.

Results

In the age-matched group, eye movements indicated agent-first predictive processing after hearing the subject noun, followed by rapid thematic reanalysis after hearing the verb form. Pretreatment eye movements in the participants with aphasia showed no predictive agent-first processing, and more accurate thematic analysis in active compared to passive sentences. After treatment, which resulted in improved offline passive sentence production and comprehension, participants were more likely to respond correctly when they made agent-first eye movements early in the sentence, showed equally reliable thematic analysis in active and passive sentences, and were less likely to use a spatially based alternative response strategy.

Conclusions

These findings suggest that treatment focused on improving sentence production and comprehension supports the emergence of more normal-like sentence comprehension processes.

Recovery of Sentence Production Processes Following Language Treatment in Aphasia: Evidence from Eyetracking

Introduction: Sentence production impairments in aphasia often improve with treatment. However, little is known about how cognitive processes supporting sentence production, such as sentence planning, are impacted by treatment.

Methods: The present study used eyetracking to examine changes in sentence production resulting from a 12-week language treatment program focused on passive sentences (Treatment of Underlying Forms (TUF); Thompson and Shapiro, 2005). In two pre-treatment and two post-treatment sessions, nine participants with mild-to-moderate agrammatic aphasia performed a structural priming task, which involved repeating primed sentences (actives or passives) and then, using the same verb, producing sentences describing pictured events. Two individuals with aphasia performed the eyetracking task on the same schedule without intervening language treatment. Ten unimpaired older adults also performed the task to identify normal performance patterns. Sentence production accuracy and speech onset latencies were examined, and eye movements to the pictured Agent and Theme characters were analyzed in the first 400 ms after picture onset, reflecting early sentence planning, and in the regions preceding the production of the sentence subject and post-verbal noun, reflecting lexical encoding.

Results: Unimpaired controls performed with high accuracy. Their early eye movements (first 400 ms) indicated equal fixations to the Agent and Theme, consistent with structural sentence planning (i.e., initial construction of an abstract structural frame). Subsequent eye movements occurring prior to speech onset were consistent with encoding of the correct sentence subject (i.e., the Agent in actives, Theme in passives), with encoding of the post-verbal noun beginning at speech onset. In participants with aphasia, accuracy improved significantly with treatment, and post-treatment (but not pre-treatment) eye movements were qualitatively similar to those of unimpaired controls, indicating correct encoding of the Agent and Theme nouns for both active and passive sentences. Analysis of early eye movements also showed a treatment-induced increase in structural planning. No changes in sentence production accuracy or eye movements were found in the aphasic participants who did not receive treatment.

Conclusion: These findings indicate that treatment improves sentence production and results in the emergence of normal-like cognitive processes associated with successful sentence production, including structural planning.

Reading and listening in people with aphasia: effects of syntactic complexity

PURPOSE

The purpose of this study was to compare online effects of syntactic complexity in written and spoken sentence comprehension in people with aphasia (PWA) and adults with no brain damage (NBD).

METHOD

The participants in Experiment 1 were NBD older and younger adults (n = 20 per group). The participants in Experiment 2 were 10 PWA. In both experiments, the participants read and listened to sentences in self-paced reading and listening tasks. The experimental materials consisted of object cleft sentences (e.g., It was the girl who the boy hugged.) and subject cleft sentences (e.g., It was the boy who hugged the girl.).

RESULTS

The predicted effects of syntactic complexity were observed in both Experiments 1 and 2: Reading and listening times were longer for the verb in sentences with object compared to subject relative clauses. The NBD controls showed exaggerated effects of syntactic complexity in reading compared to listening. The PWA did not show different modality effects from the NBD participants.

CONCLUSION

Although effects of syntactic complexity were somewhat exaggerated in reading compared with listening, both the PWA and the NBD controls showed similar effects in both modalities.

Dissociations and associations of performance in syntactic comprehension in aphasia and their implications for the nature of aphasic deficits

Sixty-one pwa were tested on syntactic comprehension in three tasks: sentence-picture matching, sentence-picture matching with auditory moving window presentation, and object manipulation. There were significant correlations of performances on sentences across tasks. First factors on which all sentence types loaded in unrotated factor analyses accounted for most of the variance in each task. Dissociations in performance between sentence types that differed minimally in their syntactic structures were not consistent across tasks. These results replicate previous results with smaller samples and provide important validation of basic aspects of aphasic performance in this area of language processing. They point to the role of a reduction in processing resources and of the interaction of task demands and parsing and interpretive abilities in the genesis of patient performance.

Rehabilitation of language in expressive aphasias: a literature review

Objective

This paper reviews the methodological characteristics of studies on rehabilitation of expressive aphasia, describing the techniques of rehabilitation used.

Methods

The databases Medline, Science Direct and PubMed were searched for relevant articles (January 1999 to December 2011) using the keywords Expressive / Broca / Nonfluent Aphasia, combined with Language or Speech Rehabilitation / Therapy / Intervention.

Results

A total of 56 articles were retrieved describing rehabilitation techniques, including 22 with a focus on lexical processing, 18 on syntax stimulation, seven with the aim of developing speech and nine with multiple foci.

Conclusion

A variety of techniques and theoretical approaches are available, highlighting the heterogeneity of research in this area. This diversity can be justified by the uniqueness of patients' language deficits, making it difficult to generalize. In addition, there is a need to combine the formal measures of tests with measures of pragmatic and social skills of communication to determine the effect of rehabilitation on the patient's daily life.

Lexical and prosodic effects on syntactic ambiguity resolution in aphasia

The purpose of this study was to determine whether and when individuals with aphasia and healthy controls use lexical and prosodic information during on-line sentence comprehension. Individuals with aphasia and controls (n = 12 per group) participated in a self-paced listening experiment. The stimuli were early closure sentences, such as "While the parents watched(,) the child sang a song." Both lexical and prosodic cues were manipulated. The cues were biased toward the subject- or object- of the ambiguous noun phrase (the child). Thus, there were two congruous conditions (in which both lexical cues and prosodic cues were consistent) and two incongruous conditions (in which lexical and prosodic cues conflicted). The results showed that the people with aphasia had longer listening times for the ambiguous noun phrase (the child) when the cues were conflicting, rather than consistent. The controls showed effects earlier in the sentence, at the subordinate verb (watched or danced). Both groups showed evidence of reanalysis at the main verb (sang). These effects demonstrate that the aphasic group was sensitive to the lexical and prosodic cues, but used them on a delayed time course relative to the control group.

Neural dynamics of animacy processing in language comprehension: ERP evidence from the interpretation of classifier-noun combinations

An event-related potential experiment was conducted to investigate the temporal neural dynamics of animacy processing in the interpretation of classifier-noun combinations. Participants read sentences that had a non-canonical structure, object noun +subject noun+verb+numeral-classifier+adjective. The object noun and its classifier were either (a) congruent, (b) incongruent, but matching in animacy, or (c) incongruent, mismatching in animacy. An N400 effect was observed for both incongruent conditions, but not for additional mismatch in animacy. When only data from participants who accepted the non-canonical structure were analyzed, the animacy mismatch elicited a P600 but still no N400. These findings suggest that animacy information is not used immediately for semantic integration of nouns and their classifiers, but is used in a later analysis reflected by P600. Thus, the temporal neural dynamics of animacy processing in sentence comprehension may be modulated by the relevance of animacy to thematic interpretation.

BOLD response to semantic and syntactic processing during hypoglycemia is load-dependent

This study investigates how syntactic and semantic load factors impact sentence comprehension and BOLD signal under moderate hypoglycemia. A dual session, whole brain fMRI study was conducted on 16 healthy participants using the glucose clamp technique. In one session, they experienced insulin-induced hypoglycemia (plasma glucose at ∼50mg/dL); in the other, plasma glucose was maintained at euglycemic levels (∼100mg/dL). During scans subjects were presented with sentences of contrasting syntactic (embedding vs. conjunction) and semantic (reversibility vs. irreversibility) load. Semantic factors dominated the overall load effects on both performance (p<0.001) and BOLD response (p<0.01, corrected). Differential BOLD signal was observed in frontal, temporal, temporo-parietal and medio-temporal regions. Hypoglycemia and syntactic factors significantly impacted performance (p=0.002) and BOLD response (p<0.01, corrected) in the reversible clause conditions, more extensively in reversible-embedded than in reversible-conjoined clauses. Hypoglycemia resulted in a robust decrease in performance on reversible clauses and exerted attenuating effects on BOLD unselectively across cortical circuits. The dominance of reversibility in all measures underscores the distinction between the syntactic and semantic contrasts. The syntactic is based in a quantitative difference in algorithms interpreting embedded and conjoined structures. We suggest that the semantic is based in a qualitative difference between algorithmic mapping of arguments in reversible clauses and heuristic linking in irreversible clauses. Because heuristics drastically reduce resource demand, the operations they support would resist the load-dependent cognitive consequences of hypoglycemia.

Binding in agrammatic aphasia: Processing to comprehension

BACKGROUND: Theories of comprehension deficits in Broca's aphasia have largely been based on the pattern of deficit found with movement constructions. However, some studies have found comprehension deficits with binding constructions, which do not involve movement. AIMS: This study investigates online processing and offline comprehension of binding constructions, such as reflexive (e.g., himself) and pronoun (e.g., him) constructions in unimpaired and aphasic individuals in an attempt to evaluate theories of agrammatic comprehension. METHODS #ENTITYSTARTX00026; PROCEDURES: Participants were eight individuals with agrammatic Broca's aphasia and eight age-matched unimpaired individuals. We used eyetracking to examine online processing of binding constructions while participants listened to stories. Offline comprehension was also tested. OUTCOMES #ENTITYSTARTX00026; RESULTS: The eye movement data showed that individuals with Broca's aphasia were able to automatically process the correct antecedent of reflexives and pronouns. In addition, their syntactic processing of binding was not delayed compared to normal controls. Nevertheless, offline comprehension of both pronouns and reflexives was significantly impaired compared to the control participants. This comprehension failure was reflected in the aphasic participants' eye movements at sentence end, where fixations to the competitor increased. CONCLUSIONS: These data suggest that comprehension difficulties with binding constructions seen in agrammatic aphasic patients are not due to a deficit in automatic syntactic processing or delayed processing. Rather, they point to a possible deficit in lexical integration.

Eye movements when reading implausible sentences: investigating potential structural influences on semantic integration

The disruption that occurs in response to reading about implausible events in unambiguous sentences can be informative about the time course of semantic interpretation (e.g., Hagoort, Hald, Bastiaansen, & Petersson, 2004; Nieuwland & Van Berkum, 2006; Warren & McConnell, 2007). Two eye-tracking studies used implausible sentences to investigate whether local factors like the structural relationships and the distance between words cueing a plausibility violation influence how quickly those words are integrated into a global semantic interpretation. Experiment 1 suggested that eye-movement disruption was unaffected by the number of words intervening between the words cueing the implausibility. Experiment 2 demonstrated that eye-movement disruption to implausibility occurred along the same time course regardless of whether the words cueing the implausibility were in a theta-assigning relation or not. These results suggest that these local structural factors do not influence how quickly new words are integrated into a semantic representation, but rather the global event representation determines the time course over which implausibility is detected.

Automatic processing of wh- and NP-movement in agrammatic aphasia: Evidence from eyetracking

Individuals with agrammatic Broca's aphasia show deficits in comprehension of non-canonical wh-movement and NP-movement sentences. Previous work using eyetracking has found that agrammatic and unimpaired listeners show very similar patterns of automatic processing for wh-movement sentences. The current study attempts to replicate this finding for sentences with wh-movement (in object relatives in the current study) and to extend it to sentences with NP movement (passives). For wh-movement sentences, aphasic and control participants' eye-movements differed most dramatically in late regions of the sentence and post-offset, with aphasic participants exhibiting lingering attention to a salient but grammatically impermissible competitor. The eye-movement differences between correct and incorrect trials for wh-movement sentences were similar, with incorrect trials also exhibiting competition from an impermissible interpretation late in the sentence. Furthermore, the two groups exhibited similar eye-movement patterns in response to passive NP-movement sentences, but showed little evidence of gap-filling for passives. The results suggest that aphasic and unimpaired individuals may generate similar representations during comprehension, but that aphasics are highly vulnerable to interference from alternative interpretations (Ferreira, 2003).

The on-line processing of verb-phrase ellipsis in aphasia

We investigate the on-line processing of verb-phrase ellipsis (VPE) constructions in two brain injured populations: Broca's and Anomic aphasics. VPE constructions are built from two simple clauses; the first is the antecedent clause and the second is the ellipsis clause. The ellipsis clause is missing its verb and object (i.e., its verb phrase (VP)), which receives its reference from the fully specified VP in the antecedent clause. VPE constructions are unlike other sentence types that require displacement of an argument NP; these latter constructions (e.g., object-relatives, wh-questions) yield either on-time or delayed antecedent reactivation. Our results demonstrate that Anomics, like unimpaired individuals, evince reactivation of the direct object NP (within the VP) at the elided position. Broca's patients, on the other hand, do not show reactivation of the antecedent. We consider several interpretations for our data, including explanations focusing on the larger 'grain size' of the reconstructed material in the ellipsis clause, the properties of the auxiliary that carries tense and agreement features, and the possibility that the cost-free syntactic copy procedure claimed to underlie VPE may be modulated by the functional deficit in Broca's aphasia.

Experience and sentence processing: statistical learning and relative clause comprehension

Many explanations of the difficulties associated with interpreting object relative clauses appeal to the demands that object relatives make on working memory. MacDonald and Christiansen [MacDonald, M. C., & Christiansen, M. H. (2002). Reassessing working memory: Comment on Just and Carpenter (1992) and Waters and Caplan (1996). Psychological Review, 109, 35-54] pointed to variations in reading experience as a source of differences, arguing that the unique word order of object relatives makes their processing more difficult and more sensitive to the effects of previous experience than the processing of subject relatives. This hypothesis was tested in a large-scale study manipulating reading experiences of adults over several weeks. The group receiving relative clause experience increased reading speeds for object relatives more than for subject relatives, whereas a control experience group did not. The reading time data were compared to performance of a computational model given different amounts of experience. The results support claims for experience-based individual differences and an important role for statistical learning in sentence comprehension processes.

Frequency of Basic English Grammatical Structures: A Corpus Analysis

Many recent models of language comprehension have stressed the role of distributional frequencies in determining the relative accessibility or ease of processing associated with a particular lexical item or sentence structure. However, there exist relatively few comprehensive analyses of structural frequencies, and little consideration has been given to the appropriateness of using any particular set of corpus frequencies in modeling human language. We provide a comprehensive set of structural frequencies for a variety of written and spoken corpora, focusing on structures that have played a critical role in debates on normal psycholinguistics, aphasia, and child language acquisition, and compare our results with those from several recent papers to illustrate the implications and limitations of using corpus data in psycholinguistic research.

Complexity in treatment of syntactic deficits

PURPOSE

This article addresses complexity in the context of treatment for sentence structural impairments in agrammatic aphasia, with emphasis on noncanonical sentences involving linguistic movement and their related counterparts. Extensions of the complexity effect to recovery of canonical sentences also are discussed, stressing the linguistic properties of verbs as well as grammatical morphology in building complexity hierarchies.

METHOD

A number of variables to consider in developing complexity hierarchies in the syntactic domain are addressed, and a series of studies using single-subject controlled experimental analysis are discussed.

RESULTS

Findings across studies show that training complex sentences results in improvement of simpler structures when, and only when, the underlying linguistic properties are shared by both. The opposite approach, training simple structures first and building to more complex ones, does not provide the full benefit of treatment, in that little or no generalization occurs across structures.

CONCLUSION

Using complex language material as a starting point for treatment of sentence structural deficits in aphasia results in cascading generalization to simpler, linguistically related material and expands spontaneous language production in many language-disordered adults with aphasia. Clinicians are, therefore, urged to adopt this approach in clinical practice, even though it is counterintuitive and departs significantly from conventional treatment methods.

Real-time comprehension of wh- movement in aphasia: evidence from eyetracking while listening

Sentences with non-canonical wh- movement are often difficult for individuals with agrammatic Broca's aphasia to understand (, inter alia). However, the explanation of this difficulty remains controversial, and little is known about how individuals with aphasia try to understand such sentences in real time. This study uses an eyetracking while listening paradigm to examine agrammatic aphasic individuals' on-line comprehension of movement sentences. Participants' eye-movements were monitored while they listened to brief stories and looked at visual displays depicting elements mentioned in the stories. The stories were followed by comprehension probes involving wh- movement. In line with previous results for young normal listeners [Sussman, R. S., & Sedivy, J. C. (2003). The time-course of processing syntactic dependencies: evidence from eye movements. Language and Cognitive Processes, 18, 143-161], the study finds that both older unimpaired control participants (n=8) and aphasic individuals (n=12) showed visual evidence of successful automatic comprehension of wh- questions (like "Who did the boy kiss that day at school?"). Specifically, both groups fixated on a picture corresponding to the moved element ("who," the person kissed in the story) at the position of the verb. Interestingly, aphasic participants showed qualitatively different fixation patterns for trials eliciting correct and incorrect responses. Aphasic individuals looked first to the moved-element picture and then to a competitor following the verb in the incorrect trials. However, they only showed looks to the moved-element picture for the correct trials, parallel to control participants. Furthermore, aphasic individuals' fixations during movement sentences were just as fast as control participants' fixations. These results are unexpected under slowed-processing accounts of aphasic comprehension deficits, in which the source of failed comprehension should be delayed application of the same processing routines used in successful comprehension. This pattern is also unexpected if aphasic individuals are using qualitatively different strategies than normals to comprehend such sentences, as under impaired-representation accounts of agrammatism. Instead, it suggests that agrammatic aphasic individuals may process wh- questions similarly to unimpaired individuals, but that this process often fails to facilitate off-line comprehension of sentences with wh- movement.

Treating agrammatic aphasia within a linguistic framework: Treatment of Underlying Forms

BACKGROUND: Formal linguistic properties of sentences-both lexical, i.e., argument structure, and syntactic, i.e., movement-as well as what is known about normal and disordered sentence processing and production, were considered in the development of Treatment of Underlying Forms (TUF), a linguistic approach to treatment of sentence deficits in patients with agrammatic aphasia. TUF is focused on complex, non-canonical sentence structures and operates on the premise that training underlying, abstract, properties of language will allow for effective generalisation to untrained structures that share similar linguistic properties, particularly those of lesser complexity. AIMS: In this paper we summarise a series of studies focused on examining the effects of TUF. METHODS #ENTITYSTARTX00026;PROCEDURES: In each study, sentences selected for treatment and for generalisation analysis were controlled for their lexical and syntactic properties, with some structures related and others unrelated along theoretical lines. We use single-subject experimental designs-i.e., multiple baseline designs across participants and behaviours-to chart improvement in comprehension and production of both trained and untrained structures. One structure was trained at a time, while untrained sentences were tested for generalisation. Participants included individuals with mild to moderately severe agrammatic, Broca's aphasia with characteristic deficits patterns. OUTCOMES #ENTITYSTARTX00026; RESULTS: Results of this work have shown that treatment improves the sentence types entered into treatment, that generalisation occurs to sentences which are linguistically related to those trained, and that treatment results in changes in spontaneous discourse in most patients. Further, we have found that generalisation is enhanced when the direction of treatment is from more to less complex structures, a finding that led to the Complexity Account of Treatment Efficacy (CATE, Thompson, Shapiro, Kiran, & Sobecks, 2003). Finally, results of recent work showing that treatment appears to affect processing of trained sentences in real time and that treatment gains can be mapped onto the brain using functional magnetic resonance imaging (fMRI) are discussed. CONCLUSIONS: These findings indicate that TUF is effective for treating sentence comprehension and production in patients who present with language deficit patterns like those seen in our patients. Patients receiving this treatment show strong generalisation effects to untrained language material. Given the current healthcare climate, which limits the amount of treatment that aphasic patients receive following stroke, it is important that clinicians deliver treatment that results in optimal generalisation in the least amount of time possible.