Verbal memory and sentence comprehension in aphasia: A case series

ABSTRACT

This case series explores the relationship between verbal memory capacity and sentence comprehension in four patients with aphasia. Two sentence comprehension tasks showed that two patients, P1 and P2, had impaired syntactic comprehension, whereas P3 and P4’s sentence comprehension was intact. The memory assessment tasks showed that P1 and P2 had severely impaired short-term memory, whereas P3 and P4 performed within the normal range in the short-term memory tasks. This finding suggests an association between short-term memory deficit and sentence comprehension difficulties. P1 and P3 exhibited impaired comparable working memory deficits, suggesting a dissociation between working memory and sentence comprehension.     

Positive effects of a computerised working memory and executive function training on sentence comprehension in aphasia

Aphasia, the language disorder following brain damage, is frequently accompanied by deficits of working memory (WM) and executive functions (EFs). Recent studies suggest that WM, together with certain EFs, can play a role in sentence comprehension in individuals with aphasia (IWA), and that WM can be enhanced with intensive practice. Our aim was to investigate whether a combined WM and EF training improves the understanding of spoken sentences in IWA. We used a pre–post-test case control design. Three individuals with chronic aphasia practised an adaptive training task (a modified n-back task) three to four times a week for a month. Their performance was assessed before and after the training on outcome measures related to WM and spoken sentence comprehension. One participant showed significant improvement on the training task, another showed a tendency for improvement, and both of them improved significantly in spoken sentence comprehension. The third participant did not improve on the training task, however, she showed improvement on one measure of spoken sentence comprehension. Compared to controls, two individuals improved at least in one condition of the WM outcome measures. Thus, our results suggest that a combined WM and EF training can be beneficial for IWA.     

The relationship between short-term memory,conflict resolution,and sentence comprehension impairments in aphasia

Background: Sentence comprehension involves the integration of multiple linguistic representations. This integration can be especially challenging when different cues lead to conflicting interpretations. Short-term memory (STM) and conflict resolution are two processes that have been previously linked to sentence comprehension and could assist in integration. However, the relation of each process to comprehension independently of the other has not been fully clarified.

Aims: We tested two patients with contrasting STM and conflict resolution profiles in different sentence comprehension tasks to evaluate the relationship between the three abilities.

Methods & Procedures: Patients completed (a) six STM tasks that tested either span or updating; (b) two executive function tasks that tested conflict resolution; and (c) three tasks that evaluated sentence comprehension.

Outcomes & Results: The patient with poorer STM and better conflict resolution had variable success in sentence comprehension that was contingent on memory load and the extent to which interpretation was supported by semantic knowledge. In contrast, the patient with good STM but slow conflict resolution demonstrated accurate comprehension across all tasks and conditions, and delayed reaction times for sentences containing conflict between cues.

Conclusions: The results provide broad support for a link between STM and sentence comprehension. They suggest that inefficient conflict resolution might be associated with slowed down but not inaccurate comprehension of sentences when other abilities, including STM, are intact. We discuss the ways in which STM and conflict resolution may and may not assist sentence comprehension in individuals with aphasia.     

失语患者的句子理解实验研究

目的分析失语患者句子语义加工特点,为言语康复训练提供依据。方法将研究对象分为2组,即20例失语患者(失语组)和20例无失语患者(对照组);实验1考察句子语义结构判断,实验2为不同句法难度句子的语义加工,实验3是复句的逻辑语义判断。结果实验组对语义结构加工明显不及对照组;对于句法难度不同的句子语义加工,实验组与对照组对于不同类型句子判断的难度顺序一致,但判断能力上有一定的差异;实验组对于关联词语与肢命题的逻辑语义关系的分析能力明显不及对照组。结论失语患者句子语义加工特点不同,应作为针对性制定康复计划的客观依据。     

The treatment of an auditory working memory deficit and the implications for sentence comprehension abilities in mild "receptive" aphasia

Background: Theoretical studies have shown that some deficits in verbal short-term/working memory can impact comprehension abilities. Clinicians often suspect that their clients are failing to understand speech because they cannot remember what has been said. Yet there are no reports of how to treat such a problem. Aims: To see if improving the short-term/working memory abilities of a person with aphasia would improve her comprehension at the sentence level. In addition, we sought to explore the issues involved in carrying out research-based therapy in a clinical environment. Methods & Procedures: The memory and language impairments of a person with aphasia were assessed. The memory impairments were then targeted in therapy by requiring the repetition of gradually more demanding sentences. Comprehension itself was not practised at all during therapy. Outcome and Results: Certain aspects of short-term and working memory improved post-therapy, notably an increase in digit span and an ability to repeat more words in sentences. There was a limited generalisation of improvement to comprehension tasks, meaning that the client could understand longer sentences and required fewer repetitions. The existence of possible additional impairments was revealed post-therapy. Conclusions: If memory limitations are causing comprehension difficulty, therapy may need to take the focus away from language and on to short-term/working memory. However, improvement may be limited. In addition, we suggest that within the context of a clinical setting, a reasonable balance between research and therapy can be struck (albeit with some difficulty) if compromises are made.     

Reading comprehension treatment in aphasia: a systematic review

Background: Reading difficulties often present as a consequence of aphasia. The specific nature of reading deficits varies widely in manifestation, and the cause of these deficits may be the result of a phonological, lexical semantic, or cognitive impairment. Several treatments have been developed to address a range of impairments underlying reading difficulty.

Aims: The purpose of this review is to describe the current research on reading comprehension treatments for persons with aphasia, assess the quality of the research, and summarize treatment outcomes.

Methods & Procedures: A systematic review of the literature was conducted based on a set of a priori questions, inclusion/exclusion criteria, and pre-determined search parameters. Results were summarized according to treatment type, methodologic rigor, and outcomes.

Outcomes & Results: Fifteen studies meeting criteria were identified. A variety of reading comprehension treatments was implemented including: oral reading, strategy-based, cognitive treatment, and hierarchical reading treatments. Quality ratings were highly variable, ranging from 3 to 9 (on a 12-point scale). Overall, 14 of the 18 individuals for whom individual data were provided demonstrated some degree of improvement (oral reading 4/5 participants, strategy based 4/6, and cognitive treatment 6/7). Gains were also evident for hierarchical reading treatment administered to participant groups via computer; however, the degree to which improvement reached statistical significance varied among studies.

Conclusions: Reading comprehension treatments have the potential to improve reading comprehension ability in persons with aphasia; however, outcomes were variable within and among treatment methods. We suggest focusing future research on factors such as participant candidacy and treatment intensity using increased methodological rigor.     

Short-term and working memory impairments in aphasia

The aim of the present study is to investigate short-term memory and working memory deficits in aphasics in relation to the severity of their language impairment. Fifty-eight aphasic patients participated in this study. Based on language assessment, an aphasia score was calculated for each patient. Memory was assessed in two modalities, verbal and spatial. Mean scores for all memory tasks were lower than normal. Aphasia score was significantly correlated with performance on all memory tasks. Correlation coefficients for short-term memory and working memory were approximately of the same magnitude. According to our findings, severity of aphasia is related with both verbal and spatial memory deficits. Moreover, while aphasia score correlated with lower scores in both short-term memory and working memory tasks, the lack of substantial difference between corresponding correlation coefficients suggests a possible primary deficit in information retention rather than impairment in working memory.     

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

Background & Aims: 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 & Procedures: 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.     

A longitudinal study of sentence comprehension difficulty in primary progressive aphasia

CONTEXT: Patients with primary progressive aphasia have sentence comprehension difficulty, but the longitudinal course of this deficit has not been investigated. OBJECTIVE: To determine how grammatical, single word meaning, and working memory factors contribute to longitudinal decline of sentence comprehension in primary progressive aphasia. We hypothesised partially distinct patterns of sentence comprehension difficulty in subgroups of patients with progressive non-fluent aphasia (PNFA) and semantic dementia (SD). DESIGN: Cohort. SETTING: Institutional out patient referral centre. PATIENTS: PNFA (n = 14), SD (n = 10). MAIN OUTCOME MEASURE: Sentence comprehension accuracy. RESULTS: PNFA patients were significantly impaired at understanding grammatically complex sentences when first seen, and this was more evident than impairment of their comprehension of grammatically simple sentences (p<0.05). Comprehension of grammatically complex sentences correlated with their working memory deficit at presentation (p<0.05). PNFA patients showed modest decline over time in grammatical comprehension. In SD, comprehension of grammatically complex sentences was not more impaired than comprehension of grammatically simple sentences when first seen, but these patients demonstrated a significant longitudinal decline in understanding grammatically complex sentences (p<0.05). Cox regression analyses showed that a deficit in single word meaning contributes to the progressive impairment for grammatically complex sentences in SD (p<0.05), but working memory does not contribute to longitudinal decline in PNFA. CONCLUSION: Patients with PNFA and SD have sentence comprehension difficulty, but distinct factors contribute to this impairment during the course of their disease.     

Real-time processing in reading sentence comprehension for normal adult individuals and persons with aphasia

Abstract

One cannot but be grateful to Jon Lyon for his comprehensive review of the literature relating communication and drawing. He has clearly stated the benefits of drawing in aphasia therapy, and has equally clearly addressed the limitations. Because my attempts at therapy tend to emphasize compensationsfor more natural communication modes, drawing has a continuously alluring pull. Perhaps the most interesting part of Lyon's paper to me is his comments that directly relate to patients. Thus, my comments will be limited to additional patient information and some questions generated as a result.     

Lexical access rate of closed-class elements during auditory sentence comprehension in adults with aphasia

Background: One hypothesis regarding the underlying impairment in agrammatic comprehension suggests that individuals with this disorder suffer from a reduction in lexical activation of closed-class words and therefore cannot appropriately construct a syntactic frame on which lexical semantic information can be applied (Friederici, 1988). Aims: Given the temporally based hypothesis, this investigation examined the effects of increased inter-word intervals (IWI) following closed-class words on auditory comprehension of various sentence types by individuals with agrammatic comprehension. It was hypothesised that providing a longer temporal window for access and processing of closedclass words would improve sentence structure comprehension. Methods & Procedures: Twelve adults with aphasia participated in an agent identification task given varying auditory sentence stimuli. Six sentence types and six IWI durations served as independent variable while accuracy and response times were measured. Outcomes & Results: Results indicated that auditory sentence comprehension performance improves when IWIs are increased. However, differences exist among individuals in response to specific IWI durations. Conclusions: Implications of delayed access rates of closed-class words in agrammatic comprehension are discussed.     

Neural basis for sentence comprehension: grammatical and short-term memory components

We monitored regional cerebral activity with BOLD fMRI while subjects were presented written sentences differing in their grammatical structure (subject-relative or object-relative center-embedded clauses) and their short-term memory demands (short or long antecedent-gap linkages). A core region of left posterior superior temporal cortex was recruited during all sentence conditions in comparison to a pseudofont baseline, suggesting that this area plays a central role in sustaining comprehension that is common to all sentences. Right posterior superior temporal cortex was recruited during sentences with long compared to short antecedent-gap linkages regardless of grammatical structure, suggesting that this brain region supports passive short-term memory during sentence comprehension. Recruitment of left inferior frontal cortex was most clearly associated with sentences that featured both an object-relative clause and a long antecedent-gap linkage, suggesting that this region supports the cognitive resources required to maintain long-distance syntactic dependencies during the comprehension of grammatically complex sentences.     

Role for memory capacity in sentence comprehension: Evidence from acute stroke

Background: Previous research has suggested that short-term and working memory (WM) resources play a critical role in sentence comprehension, especially when comprehension mechanisms cannot rely on semantics alone. However, few studies have examined this association in participants in acute stroke, before the opportunity for therapy and reorganisation of cognitive functions.

Aims: The present study examined the hypothesis that severity of short-term memory (STM) deficit due to acute stroke predicts the severity of impairment in the comprehension of syntactically complex sentences. Furthermore, we examined the association between damage to the short-term and WM network and impaired sentence comprehension, as an association would be predicted by the previous hypothesis.

Methods & Procedures: Forty-seven participants with acute stroke and 14 participants with a transient ischemic attack (TIA; the control group) were included in the present study. Participants received a language battery and clinical or research scans within 48 hrs of hospital admittance. The present study focused on the behavioural data from the STM and WM span tasks and a sentence-picture matching comprehension task included in this battery. Using regression analyses, we examined whether short-term and WM measures explained significant variance in sentence comprehension performance.

Outcomes & Results: Consistent with prior research, STM explained significant variance in sentence comprehension performance in acute stroke; in contrast, WM accounted for little variance beyond that which was already explained by STM. Furthermore, ischemia that included the short-term/WM network was sufficient to cause sentence comprehension impairments for syntactically complex sentences.

Conclusions: The present study suggests that STM resources are an important source of sentence comprehension impairments.     

The contribution of working memory to language comprehension: differential effect of aphasia type

Background: Experimental studies of short-term memory and working memory (WM) in aphasia fail to discriminate cognitive impairments of different aphasia types—non-fluent, Broca-type aphasia and fluent, Wernicke-type aphasia. However, based on the varying fundamental features of these two aphasia syndromes, the potentially different underlying mechanisms of impairment and scant preliminary evidence of varying cognitive deficits, a differential relationship between cognitive function and language processing in these two groups can be predicted.

Aims: The current study investigates the hypothesis concerning the differential impact of cognitive impairments in individuals with fluent versus non-fluent aphasia types.

Methods & Procedures: Participants with fluent (n = 19) and non-fluent (n = 16) aphasia and participants without brain damage (n = 36) were presented with an eye-tracking WM task. Additionally, individuals with aphasia completed two language comprehension tasks.

Outcomes & Results: Results revealed significant decrease in WM capacity in individuals with aphasia compared with participants without brain damage. The two aphasia groups performed similarly on the WM and language tasks. Furthermore, for participants with non-fluent aphasia, it was revealed that WM makes a significant contribution to language comprehension, while for fluent individuals this relationship was not significant.

Conclusions: Overall, the present data support the claim that there are cognitive deficits in aphasia and that these cognitive deficits tend to exacerbate the language impairments of persons with non-fluent aphasia types. The results are discussed in the context of varying mechanisms of impairment in different types of aphasia. The present findings have important implications both for the assessment and the treatment of individuals with aphasia and for understanding the nature of aphasia.     

The neural basis of reversible sentence comprehension: evidence from voxel-based lesion symptom mapping in aphasia

We explored the neural basis of reversible sentence comprehension in a large group of aphasic patients (n = 79). Voxel-based lesion symptom mapping revealed a significant association between damage in temporo-parietal cortex and impaired sentence comprehension. This association remained after we controlled for phonological working memory. We hypothesize that this region plays an important role in the thematic or what-where processing of sentences. In contrast, we detected weak or no association between reversible sentence comprehension and the ventrolateral pFC, which includes Broca's area, even for syntactically complex sentences. This casts doubt on theories that presuppose a critical role for this region in syntactic computations.     

Verb and sentence production and comprehension in aphasia: Northwestern Assessment of Verbs and Sentences (NAVS)

Background: Verbs and sentences are often impaired in individuals with aphasia, and differential impairment patterns are associated with different types of aphasia. With currently available test batteries, however, it is challenging to provide a comprehensive profile of aphasic language impairments because they do not examine syntactically important properties of verbs and sentences.

Aims: This study presents data derived from the Northwestern Assessment of Verbs and Sentences (NAVS; Thompson, 2011 Thompson, C. K. 2011. Northwestern Assessment of Verbs and Sentences Evanston, IL [Google Scholar]), a new test battery designed to examine syntactic deficits in aphasia. The NAVS includes tests for verb naming and comprehension, and production of verb argument structure in simple active sentences, with each examining the effects of the number and optionality of arguments. The NAVS also tests production and comprehension of canonical and non-canonical sentences.

Methods & Procedures: A total of 59 aphasic participants (35 agrammatic and 24 anomic) were tested using a set of action pictures. Participants produced verbs or sentences for the production subtests and identified pictures corresponding to auditorily provided verbs or sentences for the comprehension subtests.

Outcomes & Results: The agrammatic group, compared to the anomic group, performed significantly more poorly on all subtests except verb comprehension, and for both groups comprehension was less impaired than production. On verb naming and argument structure production tests both groups exhibited difficulty with three-argument verbs, affected by the number and optionality of arguments. However, production of sentences using three-argument verbs was more impaired in the agrammatic, compared to the anomic, group. On sentence production and comprehension tests, the agrammatic group showed impairments in all types of non-canonical sentences, whereas the anomic group exhibited difficulty primarily with the most difficult, object relative, structures.

Conclusions: Results show that verb and sentence deficits seen in individuals with agrammatic aphasia are largely influenced by syntactic complexity; however, individuals with anomic aphasia appear to exhibit these impairments only for the most complex forms of verbs and sentences. The present data indicate that the NAVS is useful for characterising verb and sentence deficits in people with aphasia.     

Reciprocal scaffolding treatment: A person with aphasia as clinical teacher

Background: Reciprocal Scaffolding Treatment (RST) is one of several potentially beneficial life participation approaches for aphasia. In RST, treatment occurs during genuine, relevant, and context dependent interactions that represent goals at the activity and participation levels of the World Health Organization International Classification of Functioning, Disability and Health (ICF; World Health Organization, 2001) and is based on an apprenticeship model of learning where novices are taught skills by a more skilled partner. RST was used to construct a communicatively challenging environment in which an expert with aphasia (AE) taught novices (graduate student clinicians) how to communicate with persons with aphasia in the context of conversation group treatment sessions. This is in contrast to many treatment techniques when the person with aphasia is the novice who is trying to relearn communication skills during treatment sessions with a speech‐language pathologist as the expert.

Aims: The goal of the study was to investigate the effect of RST on improvement in word retrieval and conversational components in an individual with anomic aphasia.

Methods & Procedures: This was a case study using pretreatment – post treatment assessment. The independent variable was application of RST and the contextual variables were the presence of novices (graduate student clinicians) and unfamiliar conversation partners (undergraduate speech‐language pathology students). The dependent variables were scores on a word fluency task (FAS) and conversational measures (CIUs and TTR). Over the course of a seven week training period, AE taught communication strategies to four novice graduate student clinicians, who used the strategies in conversation groups composed of 3 to 4 persons with aphasia.

Outcomes & Results: The individual with aphasia made positive changes in word fluency, Correct Information Units and Type‐Token Ratio.

Conclusions: These findings, while preliminary in nature, show how the authentic use of language in structured reciprocal interactions such as teaching may improve language. A reciprocal teaching environment carries with it the expectation that at least one participant have an intent to participate as an expert in order to convey information to novices. We speculate that the combination of reciprocal interaction and the intent to convey information, in this case in a unique manner, support improved language skills.     

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 & 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 & 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.