The time-course of lexical activation during sentence comprehension in people with aphasia

Rate of speech affects the comprehension of pronouns in children with developmental language disorder

This study examined whether children with Developmental Language Disorder (DLD) have knowledge of binding principles (i.e., linking pronouns to their structurally licensed antecedent) during real-time sentence processing (cross-modal priming, real-time) and overt comprehension (sentence-picture matching, interpretative) and whether rate of speech impacted access to that knowledge. Fourteen children with DLD participated in two experiments, with sentences presented auditorily at either a regular or slow speech rate. Sentences were matched except to contain a pronoun, reflexive, or noun phrase (control) in the same syntactic position. Experiment (1) used a cross-modal picture priming paradigm to test real-time pronoun-antecedent linking abilities at both rates of speech. Children were instructed to make a binary decision during the uninterrupted auditory presentation of a sentence to a visually presented image (of the antecedent) at the offset of a pronoun, a reflexive, or a control noun. Response times between conditions (e.g., pronoun vs. control noun) were compared to determine whether participants showed evidence of facilitative priming (faster response times in the pronoun than control noun condition) at either speech rate. Experiment (2) used an auditory sentence-picture-matching task to test final comprehension of similar sentences containing a pronoun or reflexive. Accuracy was compared across both speech rates. For Experiment (1), children with DLD did not show evidence of real-time pronoun-antecedent priming at the regular speech rate. However, when sentences were slowed, they showed facilitative priming for the pronoun condition. For experiment (2), children with DLD performed at-chance when interpreting sentences with pronouns regardless of speech rate. While children with DLD have been shown to have difficulty processing sentences containing anaphors (such as pronouns), results suggest that this is not due to loss of intrinsic knowledge of binding principles. By slowing the rate of speech input, we showed that children with DLD do have access to that knowledge and can make the correct link during real-time processing between a pronoun and its structurally licensed antecedent (Experiment 1) but need more time to do so. However, the effect of slowed speech input does not extend to final comprehension (Experiment 2).

Modulating Complex Sentence Processing in Aphasia Through Attention and Semantic Networks

PURPOSE

Lexical processing impairments such as delayed and reduced activation of lexical-semantic information have been linked to syntactic processing disruptions and sentence comprehension deficits in individuals with aphasia (IWAs). Lexical-level deficits can also preclude successful lexical encoding during sentence processing and amplify the processing costs of similarity-based interference during syntactic retrieval. We investigate whether two manipulations to engage attention and pre-activate semantic features of a target (to-be-retrieved) noun will (a) boost lexical activation during initial lexical encoding and (b) facilitate syntactic dependency linking through improved resolution of interference in IWAs and neurologically unimpaired age-matched controls (AMCs).

METHOD

Eye-tracking-while-listening with a visual world paradigm was used to investigate whether semantic and attentional manipulations modulated initial lexical processing and downstream syntactic retrieval of the direct-object noun in object-relative sentences.

RESULTS

In the attention and semantic manipulations, the AMC group showed no changes in initial lexical access levels; however, gaze patterns revealed clear facilitations in dependency linking and interference resolution. In the IWA group, the attentional cue increased and maintained activation of N1 with modest facilitations in dependency linking. In the semantic condition, IWA results showed a greater degree of facilitation during dependency linking.

CONCLUSIONS

The results suggest that attention and semantic activation are parameters that may be manipulated to strengthen encoding of lexical representations to facilitate retrieval (i.e., dependency linking) and mitigate similarity-based interference. In IWAs, these manipulations may help to reduce lexical processing deficits that can preclude successful encoding.

Bridging the Divide: Brain and Behavior in Developmental Language Disorder

Developmental language disorder (DLD) is a heterogenous neurodevelopmental disorder that affects a child's ability to comprehend and/or produce spoken and/or written language, yet it cannot be attributed to hearing loss or overt neurological damage. It is widely believed that some combination of genetic, biological, and environmental factors influences brain and language development in this population, but it has been difficult to bridge theoretical accounts of DLD with neuroimaging findings, due to heterogeneity in language impairment profiles across individuals and inconsistent neuroimaging findings. Therefore, the purpose of this overview is two-fold: (1) to summarize the neuroimaging literature (while drawing on findings from other language-impaired populations, where appropriate); and (2) to briefly review the theoretical accounts of language impairment patterns in DLD, with the goal of bridging the disparate findings. As will be demonstrated with this overview, the current state of the field suggests that children with DLD have atypical brain volume, laterality, and activation/connectivity patterns in key language regions that likely contribute to language difficulties. However, the precise nature of these differences and the underlying neural mechanisms contributing to them remain an open area of investigation.

Using lexical semantic cues to mitigate interference effects during real-time sentence processing in aphasia

We examined the auditory sentence processing of neurologically unimpaired listeners and individuals with aphasia on canonical sentence structures in real-time using a visual-world eye-tracking paradigm. The canonical sentence constructions contained multiple noun phrases and an unaccusative verb, the latter of which formed a long-distance dependency link between the unaccusative verb and its single argument (which was base generated in the object position and then displaced to the subject position). To explore the likelihood of similarity-based interference during the real time linking of the verb and the sentence's subject noun, we manipulated the animacy feature of the noun phrases (matched or mismatched). The study's objectives were to examine whether (a) reducing the similarity-based interference by mismatching animacy features would modulate the encoding and retrieval dynamics of noun phrases in real-time; and (b) whether individuals with aphasia would demonstrate on time sensitivity to this lexical-semantic cue. Results revealed a significant effect of this manipulation in individuals both with and without aphasia. In other words, the mismatch in the representational features of the noun phrases increased the distinctiveness of the unaccusative verb's subject target at the time of syntactic retrieval (verb offset) for individuals in both groups. Moreover, individuals with aphasia were shown to be sensitive to the lexical-semantic cue, even though they appeared to process it slower than unimpaired listeners. This study extends to the cue-based retrieval model by providing new insight on the real-time mechanisms underpinning sentence comprehension.

Repetition Priming Treatment for Anomia: Effects of Single- and Multiple-Exemplar Protocols

INTRODUCTION

Repetition priming can lead to improved naming ability in people with aphasia, but concerns have arisen from prior research about using only a single picture exemplar for each target. Specifically, it is unclear whether the observed improvements were due to learning simple correspondences between particular words and pictures rather than changes at a deeper level of lexical-semantic processing. In addition, implications for generalization after training with single exemplars were unclear. This study replicated and extended previous work to address these questions.

METHOD

Five participants with chronic aphasia participated in this repeated-measures design study, which repeatedly paired words and pictures with no feedback provided. Two participants engaged in a single-exemplar condition, with a single picture exemplar of each target used for every presentation of that target. The remaining three participants engaged in a multiple-exemplar condition, with several different pictures used for each target. Half of these targets used training pictures during naming probes, whereas half did not.

RESULTS

Primed items led to greater improvements in naming than items that were practiced but not primed. The data indicate that improvements may extend beyond stimulus-specific correspondences. Maintenance and generalization effects were mixed.

CONCLUSIONS

These data provide further support for the efficacy of repetition priming treatment for anomia. Implications and future directions are discussed.

A reconceptualization of sentence production in post-stroke agrammatic aphasia: the synergistic processing bottleneck model

The language production deficit in post-stroke agrammatic aphasia (PSA-G) tends to result from lesions to the left inferior frontal gyrus (LIFG) and is characterized by a triad of symptoms: fragmented sentences, errors in functional morphology, and a dearth of verbs. Despite decades of research, the mechanisms underlying production patterns in PSA-G have been difficult to characterize. Two major impediments to progress may have been the view that it is a purely morphosyntactic disorder and the (sometimes overzealous) application of linguistic theory without interceding psycholinguistic evidence. In this paper, empirical evidence is examined to present an integrated portrait of language production in PSA-G and to evaluate the assumption of a syntax-specific syndrome. In light of extant evidence, it is proposed that agrammatic language production results from a combination of morphosyntactic, phonomotor, and processing capacity limitations that cause a cumulative processing bottleneck at the point of articulatory planning. This proposed Synergistic Processing Bottleneck model of PSA-G presents a testable framework for future research. The paper ends with recommendations for future research on PSA-G.

The effect of time on lexical and syntactic processing in aphasia

Processing deficits at the lexical level, such as delayed and reduced lexical activation, have been theorized as the source of breakdowns in syntactic operations and thus contribute to sentence comprehension deficits in individuals with aphasia (IWA). In the current study, we investigate the relationship between lexical and syntactic processing in object-relative sentences using eye-tracking while listening in IWA. We explore whether manipulating the time available to process a critical lexical item (the direct-object noun) when it is initially heard in a sentence has an immediate effect on lexical access as well as a downstream effect on syntactic processing. To achieve this aim, we use novel temporal manipulations to provide additional time for lexical processing to occur. In addition to exploring these temporal effects in IWA, we also seek to understand the effect that additional time has on sentence processing in neurotypical age-matched adults (AMC). We predict that the temporal manipulations designed to provide increased processing time for critical lexical items will 1) enhance lexical processing of the target noun, 2) facilitate syntactic integration, and 3) improve sentence comprehension for both IWA and AMC. We demonstrate that strengthening lexical processing via the addition of time can affect lexical processing and facilitate syntactic retrieval of the target noun and lead to enhanced interference resolution in both unimpaired and impaired systems. In aphasia, additional time can mitigate impairments in spreading activation thereby improving lexical access and reducing interference during downstream dependency linking. However, individuals with aphasia may require longer additions of time to fully realize these benefits.

Assessment of verb and sentence processing deficits in stroke-induced aphasia: the Italian version of the Northwestern Assessment of Verbs and Sentences (NAVS-I)

Background

The Northwestern Assessment of Verbs and Sentences (NAVS) assesses verb and sentence production and comprehension in aphasia. Results from the original English version and from its adaptation to German have shown that the NAVS is able to capture effects of verb-argument structure (VAS) complexity (i.e., lower accuracy for two- and three-argument vs. one-argument verbs) and syntactic complexity (i.e., lower accuracy for non-canonical vs. canonical sentences) in both agrammatic participants and individuals with mild (residual) forms of aphasia. The NAVS has been recently adapted to Italian (NAVS-I) and tested on a group of healthy participants, with results showing longer reaction times to complex vs. simple verbs and sentences.

Aims

The present study aimed to test the ability of NAVS-I to i) capture verb/sentence production and comprehension deficits in Italian-speaking individuals with agrammatism or with fluent aphasia, and ii) differentiate individuals with aphasia from healthy age-matched participants, with the overall goal to validate its use in clinical practice.

Methods & Procedures

Forty-four healthy participants and 28 individuals with aphasia (10 with agrammatic speech production) were administered the NAVS-I, which includes tasks assessing production and comprehension of verbs requiring one, two or three arguments, as well as production and comprehension of canonical and non-canonical sentences.

Outcomes & Results

On the Verb Naming Task (VNT), better production of one- (vs. two- and three-) argument verbs was found in the agrammatic group, whereas, verb production in the fluent group was solely predicted by word length and imageability. No effects of argument optionality (i.e., greater difficulty for optionally transitive verbs than for 1-argument verbs) were found. Sentence-level tasks found no differences between the agrammatic and the fluent group in production or comprehension of both canonical and non-canonical sentences; rather, sentence comprehension accuracy was predicted by demographic variables and by aphasia severity. At the individual level, performance on the NAVS-I was significantly different from that of healthy speakers in 26/28 patients.

Conclusions

Data show that the NAVS-I is able to capture effects of argument structure complexity in verb production, and effects of syntactic complexity in sentence production and comprehension. In addition, our results point to verb production as the task with greater capability to differentiate agrammatism from other (fluent) forms of aphasia. The study provides support for the use of the NAVS-I in the diagnosis of aphasia, as it is able to detect language deficits at the individual level, even in participants with mild (residual) forms of aphasia.

Canonicity Effect on Sentence Processing of Persian-speaking Broca's Patients

Introduction

Fundamental notions of mapping hypothesis and canonicity were scrutinized in Persian-speaking aphasics.

Methods

To this end, the performance of four age-, education-, and gender matched Persian-speaking Broca's patients and eight matched healthy controls in diverse complex structures were compared via the conduction of two tasks of syntactic comprehension and grammaticality judgment.

Results

The tested structures included subject agentive, agentive passive, object experience, subject experience, subject cleft, and object cleft constructions. Our results, while corroborating the predictions of the mapping hypothesis, showed that in structures, in which linguistic elements were substituted and dislocated out of their canonical syntactic positions, namely, agentive passive, subject experiencer, object experiencer, and object cleft constructions, Broca's problems escalated. In contrast, in those structures whose constituent concatenations were aligned with canonical syntactic structures, namely subject agentive, and cleft structures, patients had above the chance performance. Ultimately, the theoretical and clinical implications of the study were discussed.

Conclusion

The number of predicates in a sentence, predicate types (psychological and agentive), as well as semantic heuristics and canonicity all by all could be regarded as the major culprits for aphasics' poor performance.

Effect of Lexical-Semantic Cues during Real-Time Sentence Processing in Aphasia

Using a visual world eye-tracking paradigm, we investigated the real-time auditory sentence processing of neurologically unimpaired listeners and individuals with aphasia. We examined whether lexical-semantic cues provided as adjectives of a target noun modulate the encoding and retrieval dynamics of a noun phrase during the processing of complex, non-canonical sentences. We hypothesized that the real-time processing pattern of sentences containing a semantically biased lexical cue (e.g., the venomous snake) would be different than sentences containing unbiased adjectives (e.g., the voracious snake). More specifically, we predicted that the presence of a biased lexical cue would facilitate (1) lexical encoding (i.e., boosted lexical access) of the target noun, snake, and (2) on-time syntactic retrieval or dependency linking (i.e., increasing the probability of on-time lexical retrieval at post-verb gap site) for both groups. For unimpaired listeners, results revealed a difference in the time course of gaze trajectories to the target noun (snake) during lexical encoding and syntactic retrieval in the biased compared to the unbiased condition. In contrast, for the aphasia group, the presence of biased adjectives did not affect the time course of processing the target noun. Yet, at the post-verb gap site, the presence of a semantically biased adjective influenced syntactic re-activation. Our results extend the cue-based parsing model by offering new and valuable insights into the processes underlying sentence comprehension of individuals with aphasia.

The role and use of event-related potentials in aphasia: A scoping review

Event-related potentials (ERPs) can provide important insights into underlying language processes in both unimpaired and neurologically impaired populations and may be particularly useful in aphasia. This scoping review was conducted to provide a comprehensive summary of how ERPs have been used with people with aphasia (PWA), with the goal of exploring the potential clinical application of ERPs in aphasia assessment and treatment. We identified 117 studies that met inclusionary criteria, reflecting six thematic domains of inquiry that relate to understanding both unimpaired and aphasic language processing and the use of ERPs with PWA. In these studies, a wide variety of ERP components were reported. Inconsistencies in reporting of participant characteristics and study protocols limit our ability to generalize beyond the individual studies and understand implications for clinical applicability. We discuss the potential roles of ERPs in aphasia management and make recommendations for further developing ERPs for clinical utility in PWA.

A Computational Evaluation of Two Models of Retrieval Processes in Sentence Processing in Aphasia

Can sentence comprehension impairments in aphasia be explained by difficulties arising from dependency completion processes in parsing? Two distinct models of dependency completion difficulty are investigated, the Lewis and Vasishth (2005) activation-based model and the direct-access model (DA; McElree, 2000). These models' predictive performance is compared using data from individuals with aphasia (IWAs) and control participants. The data are from a self-paced listening task involving subject and object relative clauses. The relative predictive performance of the models is evaluated using k-fold cross-validation. For both IWAs and controls, the activation-based model furnishes a somewhat better quantitative fit to the data than the DA. Model comparisons using Bayes factors show that, assuming an activation-based model, intermittent deficiencies may be the best explanation for the cause of impairments in IWAs, although slowed syntax and lexical delayed access may also play a role. This is the first computational evaluation of different models of dependency completion using data from impaired and unimpaired individuals. This evaluation develops a systematic approach that can be used to quantitatively compare the predictions of competing models of language processing.

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.

The time course of priming in aphasia: An exploration of learning along a continuum of linguistic processing demands

This study investigates learning in aphasia as manifested through automatic priming effects. There is growing evidence that people with aphasia have impairments beyond language processing that could affect their response to treatment. Therefore, better understanding these mechanisms would be beneficial for improving methods of rehabilitation. This study assesses semantic and repetition priming effects at varied interstimulus intervals, using stimuli that are both non-linguistic and linguistic in tasks that range from requiring nearly no linguistic processing to requiring both lexical and semantic processing. Results indicate that people with aphasia maintain typical patterns of learning across both linguistic and non-linguistic tasks as long as the implicit prime-target relationship does not depend on deep levels of linguistic processing. As linguistic processing demands increase, those with agrammatic aphasia may require more time to take advantage of learning through implicit prime-target relationships, and people with both agrammatic and non-agrammatic aphasia are more susceptible to breakdown of the semantic networks as processing demands on that system increase.

Neurocognitive Recovery of Sentence Processing in Aphasia

Purpose Reorganization of language networks in aphasia takes advantage of the facts that (a) the brain is an organ of plasticity, with neuronal changes occurring throughout the life span, including following brain damage; (b) plasticity is highly experience dependent; and (c) as with any learning system, language reorganization involves a synergistic interplay between organism-intrinsic (i.e., cognitive and brain) and organism-extrinsic (i.e., environmental) variables. A major goal for clinical treatment of aphasia is to be able to prescribe treatment and predict its outcome based on the neurocognitive deficit profiles of individual patients. This review article summarizes the results of research examining the neurocognitive effects of psycholinguistically based treatment (i.e., Treatment of Underlying Forms; Thompson & Shapiro, 2005) for sentence processing impairments in individuals with chronic agrammatic aphasia resulting from stroke and primary progressive aphasia and addresses both behavioral and brain variables related to successful treatment outcomes. The influences of lesion volume and location, perfusion (blood flow), and resting-state neural activity on language recovery are also discussed as related to recovery of agrammatism and other language impairments. Based on these and other data, principles for promoting neuroplasticity of language networks are presented. Conclusions Sentence processing treatment results in improved comprehension and production of complex syntactic structures in chronic agrammatism and generalization to less complex, linguistically related structures in chronic agrammatism. Patients also show treatment-induced shifts toward normal-like online sentence processing routines (based on eye movement data) and changes in neural recruitment patterns (based on functional neuroimaging), with posttreatment activation of regions overlapping with those within sentence processing and dorsal attention networks engaged by neurotypical adults performing the same task. These findings provide compelling evidence that treatment focused on principles of neuroplasticity promotes neurocognitive recovery in chronic agrammatic aphasia. Presentation Videohttps://doi.org/10.23641/asha.10257587.

Verb-argument integration in primary progressive aphasia: Real-time argument access and selection

BACKGROUND

Impaired sentence comprehension is observed in the three major subtypes of PPA, with distinct performance patterns relating to impairments in comprehending complex sentences in the agrammatic (PPA-G) and logopenic (PPA-L) variants and word comprehension in the semantic subtype (PPA-S). However, little is known about basic combinatory processes during sentence comprehension in PPA, such the integration of verbs with their subject and object(s) (verb-argument integration).

METHODS

The present study used visual-world eye-tracking to examine real-time verb-argument integration in individuals with PPA (12 with PPA-G, 10 with PPA-L, and 6 with PPA-S) and neurotypical older adults (15). Two baseline experiments probed eye movement control, using a non-linguistic task, and noun comprehension, respectively. Two verb-argument integration experiments examined the effects of verb meaning on (a) lexical access of the verb's direct object (argument access) and (b) selection of a semantically-appropriate direct object (argument selection), respectively. Eye movement analyses were conducted only for trials with correct behavioral responses, allowing us to distinguish accuracy and online processing.

RESULTS

The eye movement control experiment revealed no significant impairments in PPA, whereas the noun comprehension experiment revealed reduced accuracy and eye-movement latencies in PPA-S, and to a lesser extent PPA-G. In the argument access experiment, verb meaning facilitated argument access normally in PPA-G and PPA-L; in PPA-S, verb-meaning effects emerged on an atypical time course. In the argument selection experiment, significant impairments in accuracy were observed only in PPA-G, accompanied by markedly atypical eye movement patterns.

CONCLUSION

This study revealed two distinct patterns of impaired verb-argument integration in PPA. In PPA-S, impaired verb-argument integration was observed in the argument access experiment, indicating impairments in basic semantic combinatory processes which likely relate to damage in ventral language pathways. In contrast, listeners with PPA-G showed marked impairments of argument selection, likely relating to damage to left inferior frontal regions.

Speed-Accuracy Trade-Offs and Adaptation Deficits in Aphasia: Finding the "Sweet Spot" Between Overly Cautious and Incautious Responding

Purpose After stroke, how well do people with aphasia (PWA) adapt to the altered functioning of their language system? When completing a language-dependent task, how well do PWA balance speed and accuracy when the goal is to respond both as quickly and accurately as possible? The current work investigates adaptation theory ( Kolk & Heeschen, 1990 ) in the context of speed-accuracy trade-offs in a lexical decision task. PWA were predicted to set less beneficial speed-accuracy trade-offs than matched controls, and at least some PWA were predicted to present with adaptation deficits, with impaired accuracy or response times attributable to speed-accuracy trade-offs. Method The study used the diffusion model ( Ratcliff, 1978 ), a computational model of response time for simple 2-choice tasks. Parameters of the model can be used to distinguish basic processing efficiency from the overall level of caution in setting response thresholds and were used here to characterize speed-accuracy trade-offs in 20 PWA and matched controls during a lexical decision task. Results Models showed that PWA and matched control groups did not differ overall in how they set response thresholds for speed-accuracy trade-offs. However, case series analyses showed that 40% of the PWA group displayed the predicted adaptation deficits, with impaired accuracy or response time performance directly attributable to overly cautious or overly incautious response thresholds. Conclusions Maladaptive speed-accuracy trade-offs appear to be present in some PWA during lexical decision, leading to adaptation deficits in performance. These adaptation deficits are potentially treatable, and clinical implications and next steps for translational research are discussed.

Priming sentence comprehension in aphasia: Effects of lexically independent and specific structural priming

PURPOSE

Impaired message-structure mapping results in deficits in both sentence production and comprehension in aphasia. Structural priming has been shown to facilitate syntactic production for persons with aphasia (PWA). However, it remains unknown if structural priming is also effective in sentence comprehension. We examined if PWA show preserved and lasting structural priming effects during interpretation of syntactically ambiguous sentences and if the priming effects occur independently of or in conjunction with lexical (verb) information.

METHODS

Eighteen PWA and 20 healthy older adults (HOA) completed a written sentence-picture matching task involving the interpretation of prepositional phrases (PP; the chef is poking the solider with an umbrella) that were ambiguous between high (verb modifier) and low attachment (object noun modifier). Only one interpretation was possible for prime sentences, while both interpretations were possible for target sentences. In Experiment 1, the target was presented immediately after the prime (0-lag). In Experiment 2, two filler items intervened between the prime and the target (2-lag). Within each experiment, the verb was repeated for half of the prime-target pairs, while different verbs were used for the other half. Participants' off-line picture matching choices and response times were measured.

RESULTS

After reading a prime sentence with a particular interpretation, HOA and PWA tended to interpret an ambiguous PP in a target sentence in the same way and with faster response times. Importantly, both groups continued to show this priming effect over a lag (Experiment 2), although the effect was not as reliable in response times. However, neither group showed lexical (verb-specific) boost on priming, deviating from robust lexical boost seen in the young adults of prior studies.

CONCLUSIONS

PWA demonstrate abstract (lexically-independent) structural priming in the absence of a lexically-specific boost. Abstract priming is preserved in aphasia, effectively facilitating not only immediate but also longer-lasting structure-message mapping during sentence comprehension.

Masked Repetition Priming Treatment for Anomia

PURPOSE

Masked priming has been suggested as a way to directly target implicit lexical retrieval processes in aphasia. This study was designed to investigate repeated use of masked repetition priming to improve picture naming in individuals with anomia due to aphasia.

METHOD

A single-subject, multiple-baseline design was used across 6 people with aphasia. Training involved repeated exposure to pictures that were paired with masked identity primes or sham primes. Two semantic categories were trained in series for each participant. Analyses assessed treatment effects, generalization within and across semantic categories, and effects on broader language skills, immediately and 3 months after treatment.

RESULTS

Four of the 6 participants improved in naming trained items immediately after treatment. Improvements were generally greater for items that were presented in training with masked identity primes than items that were presented repeatedly during training with masked sham primes. Generalization within and across semantic categories was limited. Generalization to broader language skills was inconsistent.

CONCLUSION

Masked repetition priming may improve naming for some individuals with anomia due to aphasia. A number of methodological and theoretical insights into further development of this treatment approach are discussed.

What Matters in Semantic Feature Analysis: Practice-Related Predictors of Treatment Response in Aphasia

PURPOSE

This study investigated the predictive value of practice-related variables-number of treatment trials delivered, total treatment time, average number of trials per hour, and average number of participant-generated features per trial-in response to semantic feature analysis (SFA) treatment.

METHOD

SFA was administered to 17 participants with chronic aphasia daily for 4 weeks. Individualized treatment and semantically related probe lists were generated from items that participants were unable to name consistently during baseline testing. Treatment was administered to each list sequentially in a multiple-baseline design. Naming accuracy for treated and untreated items was obtained at study entry, exit, and 1-month follow-up.

RESULTS

Item-level naming accuracy was analyzed using logistic mixed-effect regression models. The average number of features generated per trial positively predicted naming accuracy for both treated and untreated items, at exit and follow-up. In contrast, total treatment time and average trials per hour did not significantly predict treatment response. The predictive effect of number of treatment trials on naming accuracy trended toward significance at exit, although this relationship held for treated items only.

CONCLUSIONS

These results suggest that the number of patient-generated features may be more strongly associated with SFA-related naming outcomes, particularly generalization and maintenance, than other practice-related variables.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5734113.

Electrophysiology of prosodic and lexical-semantic processing during sentence comprehension in aphasia

Event-related potentials (ERPs) were used to examine how individuals with aphasia and a group of age-matched controls use prosody and themattic fit information in sentences containing temporary syntactic ambiguities. Two groups of individuals with aphasia were investigated; those demonstrating relatively good sentence comprehension whose primary language difficulty is anomia (Individuals with Anomic Aphasia (IWAA)), and those who demonstrate impaired sentence comprehension whose primary diagnosis is Broca's aphasia (Individuals with Broca's Aphasia (IWBA)). The stimuli had early closure syntactic structure and contained a temporary early closure (correct)/late closure (incorrect) syntactic ambiguity. The prosody was manipulated to either be congruent or incongruent, and the temporarily ambiguous NP was also manipulated to either be a plausible or an implausible continuation for the subordinate verb (e.g., "While the band played the song/the beer pleased all the customers."). It was hypothesized that an implausible NP in sentences with incongruent prosody may provide the parser with a plausibility cue that could be used to predict syntactic structure. The results revealed that incongruent prosody paired with a plausibility cue resulted in an N400-P600 complex at the implausible NP (the beer) in both the controls and the IWAAs, yet incongruent prosody without a plausibility cue resulted in an N400-P600 at the critical verb (pleased) only in healthy controls. IWBAs did not show evidence of N400 or P600 effects at the ambiguous NP or critical verb, although they did show evidence of a delayed N400 effect at the sentence-final word in sentences with incongruent prosody. These results suggest that IWAAs have difficulty integrating prosodic cues with underlying syntactic structure when lexical-semantic information is not available to aid their parse. IWBAs have difficulty integrating both prosodic and lexical-semantic cues with syntactic structure, likely due to a processing delay.

A rational inference approach to group and individual-level sentence comprehension performance in aphasia

The rational inference, or noisy channel, account of language comprehension predicts that comprehenders are sensitive to the probabilities of different interpretations for a given sentence and adapt as these probabilities change (Gibson, Bergen & Piantadosi, 2013). This account provides an important new perspective on aphasic sentence comprehension: aphasia may increase the likelihood of sentence distortion, leading people with aphasia (PWA) to rely more on the prior probability of an interpretation and less on the form or structure of the sentence (Gibson, Sandberg, Fedorenko, Bergen & Kiran, 2015). We report the results of a sentence-picture matching experiment that tested the predictions of the rational inference account and other current models of aphasic sentence comprehension across a variety of sentence structures. Consistent with the rational inference account, PWA showed similar sensitivity to the probability of particular kinds of form distortions as age-matched controls, yet overall their interpretations relied more on prior probability and less on sentence form. As predicted by rational inference, but not by other models of sentence comprehension in aphasia, PWA's interpretations were more faithful to the form for active and passive sentences than for direct object and prepositional object sentences. However contra rational inference, there was no evidence that individual PWA's severity of syntactic or semantic impairment predicted their sensitivity to form versus the prior probability of a sentence, as cued by semantics. These findings confirm and extend previous findings that suggest the rational inference account holds promise for explaining aphasic and neurotypical comprehension, but they also raise new challenges for the account.

The curious case of processing unaccusative verbs in aphasia

BACKGROUND

Individuals with agrammatic Broca's aphasia (IWBA) exhibit a delay in lexical activation in S-V-O word order sentences and delayed lexical reactivation in sentences that contain syntactic dependencies. This pattern is in contrast to neurologically unimpaired individuals who immediately evince lexical reactivation at the gap in sentences that contain syntactic dependencies. However, in the case of sentences that contain unaccusative verbs, neurologically unimpaired individuals also exhibit a delay in lexical reactivation. This delay provides a unique opportunity to further examine lexical delays in IWBA.

AIM

The purpose of the current studies is to investigate the online comprehension of sentences that contain unaccusative verbs in IWBA and in a group of age-matched control (AMC) individuals.

METHODS AND PROCEDURES

Cross-modal picture priming was used to test for priming of a displaced lexical item (direct object noun) immediately after the unaccusative verb (at the gap) during the ongoing auditory stream and at three additional time points downstream from the verb (500 ms, 750 ms, and 1,250 ms).

OUTCOMES AND RESULTS

Delayed reactivation of the displaced lexical item downstream from the gap (similar to prior reports of delayed reactivation with younger unimpaired listeners) for both the AMCs and the IWBA was found.

CONCLUSION

These results provide support that IWBA do not evince a delayed time course of lexical reactivation for unaccusative verbs compared to neurologically unimpaired individuals.

The comprehension of sentences with unaccusative verbs in aphasia: a test of the intervener hypothesis

BACKGROUND

It is well accepted that individuals with agrammatic Broca's aphasia have difficulty comprehending some sentences with filler-gap dependencies. While investigations of these difficulties have been conducted with several different sentence types (e.g., object relatives, Wh-questions), we explore sentences containing unaccusative verbs, which arguably have a single noun phrase (NP) that is base-generated in object position but then is displaced to surface subject position. Unaccusative verbs provide an ideal test case for a particular hypothesis about the comprehension disorder-the Intervener Hypothesis-that posits that the difficulty individuals with agrammatic Broca's aphasia have comprehending sentences containing filler-gap dependencies results from similarity-based interference caused by the presence of an intervening NP between the two elements of a syntactic chain.

AIM

To assess a particular account of the comprehension deficit in agrammatic Broca's aphasia-the Intervener Hypothesis.

METHODS & PROCEDURES

We used a sentence-picture matching task to determine if listeners with agrammatic Broca's aphasia (LWBA) and age-matched neurologically unimpaired controls (AMC) have difficulty comprehending unaccusative verbs when placed in subject relative and complement phrase (CP) constructions.

OUTCOMES & RESULTS

We found above-chance comprehension of both sentence constructions with the AMC participants. In contrast, we found above-chance comprehension of CP sentences containing unaccusative verbs but poor comprehension of subject relative sentences containing unaccusative verbs for the LWBA.

CONCLUSIONS

These results provide support for the Intervener Hypothesis, wherein the presence of an intervening NP between two elements of a filler-gap dependency adversely affects sentence comprehension.

The Auditory Comprehension of Wh-Questions in Aphasia: Support for the Intervener Hypothesis

PURPOSE

This study examines 3 hypotheses about the processing of wh-questions in both neurologically healthy adults and adults with Broca's aphasia.

METHOD

We used an eye tracking while listening method with 32 unimpaired participants (Experiment 1) and 8 participants with Broca's aphasia (Experiment 2). Accuracy, response time, and online gaze data were collected.

RESULTS

In Experiment 1, we established a baseline for how unimpaired processing and comprehension of 4 types of wh-question (subject- and object-extracted who- and which-questions) manifest. There was no unambiguous support found for any of the 3 hypotheses in Experiment 1. In Experiment 2 with the Broca's participants, however, we found significantly lower accuracy, slower response times, and increased interference in our gaze data in the object-extracted which-questions relative to the other conditions.

CONCLUSIONS

Our results provide support for the intervener hypothesis, which states that sentence constructions that contain an intervener (a lexical noun phrase) between a displaced noun phrase and its gap site result in a significant processing disadvantage relative to other constructions. We argue that this hypothesis offers a compelling explanation for the comprehension deficits seen in some participants with Broca's aphasia.

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.

Lexical decay during online sentence processing in adults with specific language impairment

PURPOSE

Decay of memory traces is an important component of many theories of working memory, but there is conflicting evidence on whether the rate of decay differs for individuals with specific language impairment (SLI) as compared to peers with typical language. The authors tested the hypothesis that adults with SLI have a slower decay rate.

METHOD

Twenty adults with SLI, ages 18-27 years, and 23 age-matched peers identified target words in sentences. Sentences were presented at normal and slow rates. Participants separately judged whether a picture and sentence matched in meaning as a measure of sentence processing efficiency.

RESULTS

After controlling for sentence processing efficiency, the group with SLI was slower to detect words in sentences. Response times for the group with SLI increased less in the slow condition as compared to the group with typical language, resulting in a Group × Presentation Rate interaction.

CONCLUSIONS

The Group × Presentation Rate interaction is consistent with a slower lexical decay rate for adults with SLI, but differences in the ability to manage interference could not be ruled out. The findings suggest that decay rate differences may play a role in the working memory limitations found in individuals with SLI.

Processing lexical ambiguity in sentential context: Eye-tracking data from brain-damaged and non-brain-damaged individuals

The purpose of the present study was to identify general and syndrome-specific deficits in the lexical processing of individuals with non-fluent and fluent aphasia compared to individuals without cognitive, neurological or language impairments. The time course of lexical access, as well as lexical selection and integration was studied using a visual-world paradigm in three groups of Russian speakers: 36 individuals in the control group, 15 individuals with non-fluent aphasia and eight individuals with fluent aphasia. Participants listened to temporarily ambiguous sentences wherein the context biased the interpretation of an ambiguous word toward one of its two meanings. In half of the experimental sentences, a reanalysis was needed upon encountering the disambiguating phrase. The effect of the length of the intervening material between the ambiguous word and the disambiguation point was additionally monitored. All groups of participants showed intact lexical access under slowed speech rate, but non-fluent participants experienced difficulties with timely activation of multiple referents. At later stages of lexical processing, they additionally demonstrated a specific impairment of reanalysis. The deficit in participants with fluent aphasia was not focalized at any specific stage of lexical processing. Rather, the breakdown of lexical processes in fluent aphasia was likely related to difficulties with the inhibition of irrelevant lexical activation, which is further supported by the finding that increased phonological distance between the ambiguous word and ambiguity resolution was influential to the offline performance in this group.

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.

Verb Transitivity Bias Affects On-line Sentence Reading in People with Aphasia

BACKGROUND

Studies of sentence comprehension in non-disordered populations have convincingly demonstrated that probabilistic cues influence on-line syntactic processing. One well-studied cue is verb argument structure bias, which refers to the probability that a verb will occur in a particular syntactic frame. According to the Lexical Bias Hypothesis, people with aphasia have difficulty understanding sentences in which the verb's argument structure bias conflicts with the sentence structure (e.g., a transitively biased verb in an intransitive sentence). This hypothesis may provide an account of why people with aphasia have difficulty understanding both simple and complex sentences.

AIMS

The purpose of this study was to test the Lexical Bias Hypothesis using an on-line measure of written sentence comprehension, self-paced reading.

METHODS PROCEDURES

The participants were ten people with aphasia and ten non-brain-damaged controls. The stimuli were syntactically simple transitive and intransitive sentences that contained transitively- or intransitively-biased verbs. For example, the transitively-biased verb "called" appeared in sentences such as "The agent called (the writer) from overseas to make an offer." The intransitively-biased verb "danced" appeared in sentences such as "The couple danced (the tango) every Friday night last summer."

OUTCOMES RESULTS

Both groups' reading times for critical segments were longer when the verb's transitivity bias did not match the sentence structure, particularly in intransitive sentences.

CONCLUSIONS

The results were generally consistent with the Lexical Bias Hypothesis, and demonstrated that lexical biases affect on-line processing of syntactically simple sentences in people with aphasia and controls.