Verbal memory function in mild aphasia

The impact of subcortical stroke-related aphasia on executive functions and working memory

Aphasia is a common post-stroke disorder characterized by impairments in speaking, listening, reading, and writing. Although cognitive impairments have been well studied in cortical aphasia, deficits associated with subcortical aphasia remain to be elucidated. The current study aimed to assess executive functions (EF) and working memory (WM) in patients with subcortical aphasia, and investigate the relationship between language abilities and cognition deficits. Participants of this research included patients with thalamus lesions (n = 9; mean age = 53.89 years) and healthy individuals (n = 9; mean age = 54.33 years). Assessment materials were the Mini-Mental State Examination (MMSE), Persian Western Aphasia Battery (P-WAB-1), digit span subtest of Adult Wechsler Test (WAIS-R), and Wisconsin Card Sorting Test (WCST). Obtained results revealed significant differences in all components of EF, as well as in WM forward and backward digit spans between patients and healthy individuals. However, investigating the relationship between MMSE and AQ scores and components of EF and WM revealed no significant difference. In conclusion, the findings of the present research indicated defects in cognitive functions, including WM and EF, in patients with subcortical stroke. Accordingly, it is crucial to provide optimal rehabilitation therapies for the improvement of language and cognitive problems upon subcortical aphasia.

Language learning in aphasia: A narrative review and critical analysis of the literature with implications for language therapy

People with aphasia (PWA) present with language deficits including word retrieval difficulties after brain damage. Language learning is an essential life-long human capacity that may support treatment-induced language recovery after brain insult. This prospect has motivated a growing interest in the study of language learning in PWA during the last few decades. Here, we critically review the current literature on language learning ability in aphasia. The existing studies in this area indicate that (i) language learning can remain functional in some PWA, (ii) inter-individual variability in learning performance is large in PWA, (iii) language processing, short-term memory and lesion site are associated with learning ability, (iv) preliminary evidence suggests a relationship between learning ability and treatment outcomes in this population. Based on the reviewed evidence, we propose a potential account for the interplay between language and memory/learning systems to explain spared/impaired language learning and its relationship to language therapy in PWA. Finally, we indicate potential avenues for future research that may promote more cross-talk between cognitive neuroscience and aphasia rehabilitation.

Identifying Verbal Short-Term Memory and Working Memory Impairments in Individuals With Latent Aphasia

Purpose This study was undertaken to explore whether measures of verbal short-term memory and working memory are sensitive to impairments in people with latent aphasia, who score within normal limits on typical aphasia test batteries. Method Seven individuals with latent aphasia and 24 neurotypical control participants completed 40 tasks from the Temple Assessment of Language and Short-term Memory in Aphasia (TALSA) that assess various aspects of verbal short-term memory, working memory, and language processing. Subtests were identified that differentiated between the two groups of participants. Results Twenty-one TALSA tasks were identified on which the participants with latent aphasia had significantly different performance than the typical control participants. All of these subtests engaged verbal short-term memory, and some involved working memory as well. Furthermore, the TALSA detected individual differences in linguistic profiles among participants with latent aphasia. Conclusions People with latent aphasia may be identified by tests that tap verbal short-term memory and working memory. In addition, the TALSA was found to be sensitive to the heterogeneity of this population. Further development of these measures will improve identification and treatment of this challenging population.

The Link Between Verbal Short-Term Memory and Anomia Treatment Gains

Purpose A significant relationship between verbal short-term memory (STM) and language performance in people with aphasia has been found across studies. However, very few studies have examined the predictive value of verbal STM in treatment outcomes. This study aims to determine if verbal STM can be used as a predictor of treatment success. Method Retrospective data from 25 people with aphasia in a larger randomized controlled trial of phonomotor treatment were analyzed. Digit and word spans from immediately pretreatment were run in multiple linear regression models to determine whether they predict magnitude of change from pre- to posttreatment and follow-up naming accuracy. Pretreatment, immediately posttreatment, and 3 months posttreatment digit and word span scores were compared to determine if they changed following a novel treatment approach. Results Verbal STM, as measured by digit and word spans, did not predict magnitude of change in naming accuracy from pre- to posttreatment nor from pretreatment to 3 months posttreatment. Furthermore, digit and word spans did not change from pre- to posttreatment or from pretreatment to 3 months posttreatment in the overall analysis. A post hoc analysis revealed that only the less impaired group showed significant changes in word span scores from pretreatment to 3 months posttreatment. Discussion The results suggest that digit and word spans do not predict treatment gains. In a less severe subsample of participants, digit and word span scores can change following phonomotor treatment; however, the overall results suggest that span scores may not change significantly. The implications of these findings are discussed within the broader purview of theoretical and empirical associations between aphasic language and verbal STM processing.

The Interaction between Semantic Representation and Episodic Memory

The experimental evidence on the interrelation between episodic memory and semantic memory is inconclusive. Are they independent systems, different aspects of a single system, or separate but strongly interacting systems? Here, we propose a computational role for the interaction between the semantic and episodic systems that might help resolve this debate. We hypothesize that episodic memories are represented as sequences of activation patterns. These patterns are the output of a semantic representational network that compresses the high-dimensional sensory input. We show quantitatively that the accuracy of episodic memory crucially depends on the quality of the semantic representation. We compare two types of semantic representations: appropriate representations, which means that the representation is used to store input sequences that are of the same type as those that it was trained on, and inappropriate representations, which means that stored inputs differ from the training data. Retrieval accuracy is higher for appropriate representations because the encoded sequences are less divergent than those encoded with inappropriate representations. Consistent with our model prediction, we found that human subjects remember some aspects of episodes significantly more accurately if they had previously been familiarized with the objects occurring in the episode, as compared to episodes involving unfamiliar objects. We thus conclude that the interaction with the semantic system plays an important role for episodic memory.

Nonverbal Working Memory as a Predictor of Anomia Treatment Success

PURPOSE

The purpose of the study was to determine (a) reliability of the spatial span as a nonverbal working memory (WM) task in individuals with aphasia, (b) whether participation in anomia treatment changed spatial span scores, and (c) the degree to which visuospatial WM predicted response to anomia treatment.

METHOD

Eight individuals with chronic aphasia were repeatedly assessed on the forward and backward conditions of the spatial span over 4 weeks while undergoing treatment for anomia. Experiment 1 assessed reliability of the spatial span conditions and determined whether span scores changed after beginning anomia treatment. Experiment 2 investigated the spatial span as a predictor of anomia treatment success.

RESULTS

Results of Experiment 1 showed that 7 participants demonstrated stability of the forward condition of the spatial span, and 5 participants demonstrated stability of the backward condition across all sessions (p = .05). No participants showed an effect of aphasia treatment on span performance in either condition. Experiment 2 found that the backward span condition significantly predicted anomia treatment effect size, F(1, 6) = 15.202, p = .008.

CONCLUSIONS

Visuospatial WM abilities were highly predictive of response to anomia treatment, supporting an account of WM that includes a central processing mechanism.

Psychophysiological Analysis of the Influence of Vasopressin on Speech in Patients with Post-Stroke Aphasias

Speech is an attribute of the human species. Central speech disorders following stroke are unique models for the investigation of the organization of speech. Achievements in neurobiology suggest that there are possible neuroendocrine mechanisms involved in the organization of speech. It is known that the neuropeptide vasotocin, analogous of vasopressin in mammals, modulates various components of vocalization in animals. Furthermore, the positive influence of vasopressin on memory, which plays an important role in the formation of speech, has been described. In this study, speech organization processes and their recovery with the administration of vasopressin (1-desamino-8-D-arginin-vasopressin) to 26 patients with chronic aphasias after stroke were investigated. Results showed that sub-endocrine doses of the neuropeptide with intranasal administration had positive influence primarily on simple forms of speech and secondarily on composite forms. There were no statistically significant differences between the sensory and integrative components of the organization of speech processes with vasopressin. In all cases, the positive effect of the neuropeptide was demonstrated. As a result of the effects, speech regulated by both brain hemispheres improved. It is suggested that the neuropeptide optimizes the activity both in the left and right hemispheres, with primary influence on the right hemisphere. The persistence of the acquired effects is explained by an induction of compensatory processes resulting in the reorganization of the intra-central connections by vasopressin.

The pivotal role of semantic memory in remembering the past and imagining the future

Episodic memory refers to a complex and multifaceted process which enables the retrieval of richly detailed evocative memories from the past. In contrast, semantic memory is conceptualized as the retrieval of general conceptual knowledge divested of a specific spatiotemporal context. The neural substrates of the episodic and semantic memory systems have been dissociated in healthy individuals during functional imaging studies, and in clinical cohorts, leading to the prevailing view that episodic and semantic memory represent functionally distinct systems subtended by discrete neurobiological substrates. Importantly, however, converging evidence focusing on widespread neural networks now points to significant overlap between those regions essential for retrieval of autobiographical memories, episodic learning, and semantic processing. Here we review recent advances in episodic memory research focusing on neurodegenerative populations which has proved revelatory for our understanding of the complex interplay between episodic and semantic memory. Whereas episodic memory research has traditionally focused on retrieval of autobiographical events from the past, we also include evidence from the recent paradigm shift in which episodic memory is viewed as an adaptive and constructive process which facilitates the imagining of possible events in the future. We examine the available evidence which converges to highlight the pivotal role of semantic memory in providing schemas and meaning whether one is engaged in autobiographical retrieval for the past, or indeed, is endeavoring to construct a plausible scenario of an event in the future. It therefore seems plausible to contend that semantic processing may underlie most, if not all, forms of episodic memory, irrespective of temporal condition.

Conceptualizing and Measuring Working Memory and its Relationship to Aphasia

BACKGROUND: General agreement exists in the literature that individuals with aphasia can exhibit a working memory deficit that contributes to their language processing impairments. Though conceptualized within different working memory frameworks, researchers have suggested that individuals with aphasia have limited working memory capacity, impaired attention-control processes as well as impaired inhibitory mechanisms. However, across studies investigating working memory ability in individuals with aphasia, different measures have been used to quantify their working memory ability and identify the relationship between working memory and language performance. AIMS: The primary objectives of this article are to (1) review current working memory theoretical frameworks, (2) review tasks used to measure working memory, and (3) discuss findings from studies that have investigated working memory as they relate to language processing in aphasia. MAIN CONTRIBUTION: Though findings have been consistent across studies investigating working memory ability in individuals with aphasia, discussion of how working memory is conceptualized and defined is often missing, as is discussion of results within a theoretical framework. This is critical, as working memory is conceptualized differently across the different theoretical frameworks. They differ in explaining what limits capacity and the source of individual differences as well as how information is encoded, maintained, and retrieved. When test methods are considered within a theoretical framework, specific hypotheses can be tested and stronger conclusions that are less susceptible to different interpretations can be made. CONCLUSIONS: Working memory ability has been investigated in numerous studies with individuals with aphasia. To better understand the underlying cognitive constructs that contribute to the language deficits exhibited by individuals with aphasia, future investigations should operationally define the cognitive constructs of interest and discuss findings within theoretical frameworks.

Performance of Individuals with Left-Hemisphere Stroke and Aphasia and Individuals with Right Brain Damage on Forward and Backward Digit Span Tasks

BACKGROUND: Working memory (WM) limitations have been suggested as a significant source of the linguistic processing deficits observed in individuals with aphasia (IWA). Digits forward (DF) and digits backward (DB) span tasks are frequently used to study WM in both healthy and clinical populations. Unfortunately, only a handful of studies have explored digit span in IWA. AIMS: The purpose of the current study is to measure the DF and DB spans of IWA and compare their digit spans to a group with right brain damage, but no aphasia (RBD). Additionally, DF and DB span is compared within each group to determine if there is indeed a performance differential that may support the idea that DB is a more difficult WM task in these populations. METHODS AND PROCEDURES: Seventeen IWA and 14 individuals with RBD participated in a DF and DB span task. Modifications to the span tasks were implemented to accommodate language deficits. A series of two digits were orally presented to each participant continuing to a maximum of eight digits. There were seven trials per digit series. Participants were asked to point to the correct order of digits on a written 1-9 digit list provided on individual note cards or verbally repeat the numbers if the participant was able to do so. OUTCOMES AND RESULTS: IWA demonstrated shorter digit spans than the RBD group. Both groups performed worse on the DB span tasks than the DF span tasks. CONCLUSIONS: The results are consistent with previous studies suggesting that DB span is shorter than DF span in other populations and that there are differences in performance on digit span tasks between the two groups. The differences between RBD group and IWA may be explained by decreased attentional capacity or inefficient resource allocation in IWA, or alternatively, a deficient phonological loop. Future studies should explore these possibilities.

Interdependence of episodic and semantic memory: evidence from neuropsychology

Tulving's (1972) theory of memory draws a distinction between general knowledge (semantic memory) and memory for events (episodic memory). Neuropsychological studies have generally examined each type of memory in isolation, but theorists have long argued that these two forms of memory are interdependent. Here we review several lines of neuropsychological research that have explored the interdependence of episodic and semantic memory. The studies show that these forms of memory can affect each other both at encoding and at retrieval. We suggest that theories of memory should be revised to account for all of the interdependencies between episodic and semantic memory; they should also incorporate forms of memory that do not fit neatly into either category.

Stroke and episodic memory disorders

Memory impairments are common after stroke, and the anatomical basis for impairments may be quite variable. To determine the range of stroke-related memory impairment, we identified all case reports and group studies through the Medline database and the Science Citation Index. There is no hypothesis about memory that is unique to stroke, but there are several important facets of memory impairment after stroke: (1) Every node of the limbic system implicated in memory may be damaged by stroke but very rarely in isolation and the combination of amnesia with the associated deficits often illuminates additional aspects of memory functions. (2) Stroke produces amnesia by damage to critical convergence white matter connections of the limbic system, and stroke is the only etiology of amnesia that can delineate the entire pathway of memory and critical convergence points. (3) Stroke also impairs memory, without causing classical amnesia, by damaging brain regions responsible for cognitive processes, some modality specific and some more generally strategic, that are essential for normal learning and recall.

Impaired List Learning Is Not a General Property of Frontal Lesions

Background: List-learning tasks are frequently used to provide measures of “executive functions” that are believed necessary for successful memory performance. Small sample sizes, confounding anomia, and incomplete representation of all frontal regions have prevented consistent demonstration of distinct regional frontal effects on this task. Objective: To confirm specific effects of lesions in different frontal regions. Subjects: Forty-one patients with chronic focal frontal lesions and 38 control subjects. There were no group differences in naming scores. Methods: Two word lists were presented, one with unblocked words from related categories and one in a preblocked format. Standard measures of learning, recall, recognition, and strategies were obtained, first for the frontal group as a whole and then for large but defined frontal regions. For all measures with significant group differences, a lesion “hotspotting” method identified possible specific regional injury effects. Results: The frontal group was impaired on almost all measures, but impairments on most measures were particularly identified with lesions in the left superior frontal lobe (approximately area 9s) and some deficits in learning processes were surprisingly more prominent on the blocked list. Conclusion: Difficulty with list learning is not a general property of all frontal lesions. Lesions in different frontal regions impair list learning through specific mechanisms, and these effects may be modified by manipulations of the task structure.

Language and visuospatial impairment in a case of crossed aphasia

Crossed aphasia in dextrals (CAD) constitutes an interesting model for understanding the lateralisation and interaction of language with other cognitive functions in the brain. The authors present a study of a right-handed patient with Wernicke's aphasia following a right hemisphere cerebrovascular accident, who also had impairment in visuospatial skills. Although the patient presented a remarkable improvement in language symptoms on longitudinal follow-up, the combination of linguistic, visuospatial, and attentional impairments ultimately resulted in a persisting inability to perform complex tasks. The study of mild residual disturbances can improve our understanding of the interaction of language with other cognitive functions, going some way towards explaining the particular features found in CAD.

Working memory in aphasia: theory, measures, and clinical implications

Recently, researchers have suggested that deficits in working memory capacity contribute to language-processing difficulties observed in individuals with aphasia (e.g., I. Caspari, S. Parkinson, L. LaPointe, & R. Katz, 1998; R. A. Downey et al., 2004; N. Friedmann & A. Gvion, 2003; H. H. Wright, M. Newhoff, R. Downey, & S. Austermann, 2003). A theoretical framework of working memory can aid in our understanding of a disrupted system (e.g., after stroke) and how this relates to language comprehension and production. Additionally, understanding the theoretical basis of working memory is important for the measurement and treatment of working memory. The literature indicates that future investigations of measurement and treatment of working memory are warranted in order to determine the role of working memory in language processing.

Frequency and risk factors of vascular cognitive impairment three months after ischemic stroke in china: the Chongqing stroke study

BACKGROUND

Frequency of poststroke cognitive impairment is high in western countries, and the risk factors of poststroke cognitive impairment have not been fully understood yet. We sought to examine the frequency and risk factors of cognitive impairment after ischemic stroke in a large stroke cohort of China.

METHODS

A total of 434 consecutive patients with ischemic stroke were enrolled. The cognitive status before and 3 months after stroke was evaluated using the Informant Questionnaire on Cognitive Decline in the Elderly and the Mini-Mental State Examination, respectively. Poststroke cognitive impairment was defined as cognitive impairment with concomitant stroke, stroke-related cognitive impairment was defined as cognitive impairment developing after index stroke, and cognitive impairment after first-ever stroke was defined as cognitive impairment developing after first-ever stroke. Logistic regression analysis was used to find the risk factors of cognitive impairment after stroke.

RESULTS

(1) Frequency of poststroke cognitive impairment was 37.1%, that of stroke-related cognitive impairment was 32.2%, and that of cognitive impairment after first-ever stroke was 29.6%. (2) The patients with cognitive impairment more often had older age, low educational level, atrial fibrillation, prior stroke, everyday drinking, left carotid territory infarction, multiple lesions, embolism, and dysphasia. (3) The factors associated with poststroke cognitive impairment in logistic regression analysis were age (OR 1.215, 95% CI 1.163-1.268), low educational level (OR 2.023, 95% CI 1.171-3.494), prior stroke (OR 5.130, 95% CI 2.875-9.157), everyday drinking (OR 2.013, 95% CI 1.123-3.607), dysphasia (OR 3.994, 95% CI 1.749-9.120), and left carotid territory infarction (OR 2.685, 95% CI 1.595-4.521).

CONCLUSIONS

Cognitive impairment is common 3 months after ischemic stroke in Chinese people. Risk factors for poststroke cognitive impairment include age, low educational level, everyday drinking, prior stroke, dysphasia, and left carotid territory infarction.

California Verbal Learning Test: performance by patients with focal frontal and non-frontal lesions

Although frontal lobe lesions do not cause classic amnesia, they may disrupt learning and memory in a number of ways. To investigate in finer detail the regions of frontal injury that are associated with impaired learning and to define the cognitive processing deficits specific to each region that disrupt memory, we compared 33 patients with focal frontal injury with patients with non-frontal injury and with normal controls on a standard neuropsychological instrument, the California Verbal Learning Test (CVLT). Subgroups of patients with distinct lesion site profiles were compared in a number of learning measures. All of the subgroups of patients with frontal lesions (with one exception) had inefficient learning due to poor implementation of a strategy of subjective organization. Despite this organizational deficiency, the performance of patients with frontopolar lesions normalized across trials. Only the subgroups with lesions centred either on the left posterior dorsolateral frontal region or the posterior medial frontal region had overall impaired learning and recall. The left posterior dorsolateral frontal group was most significantly impaired on all measures. This recall impairment was secondary to a mild lexical-semantic deficit. A recognition memory deficit in the same group was due to an abnormal response bias. Several groups had a modest increase in perseverative recalls; the underlying mechanisms differed. Disruption of different cognitive processes associated with specific frontal regions underlies the varied patterns of memory impairment. This study has demonstrated even finer differentiations within the frontal region than previously known.

Descriptive study of 192 adults with speech and language disturbances

CONTEXT

Aphasia is a very disabling condition caused by neurological diseases. In Brazil, we have little data on the profile of aphasics treated in rehabilitation centers.

OBJECTIVE

To present a descriptive study of 192 patients, providing a reference sample of speech and language disturbances among Brazilians.

DESIGN

Retrospective study.

SETTING

Speech Pathology Unit linked to the Neurology Division of the Hospital das Clínicas of the Faculdade de Medicina da Universidade de São Paulo.

SAMPLE

All patients (192) referred to our Speech Pathology service from 1995 to 2000.

PROCEDURES

We collected data relating to demographic variables, etiology, language evaluation (functional evaluation, Boston Diagnostic Aphasia Examination, Boston Naming and Token Test), and neuroimaging studies.

MAIN MEASUREMENTS

The results obtained in language tests and the clinical and neuroimaging data were organized and classified. Seventy aphasics were chosen for constructing a profile. Fourteen subjects with left single-lobe dysfunction were analyzed in detail. Seventeen aphasics were compared with 17 normal subjects, all performing the Token Test.

RESULTS

One hundred subjects (52%) were men and 92 (48%) women. Their education varied from 0 to 16 years (average: 6.5; standard deviation: 4.53). We identified the lesion sites in 104 patients: 89% in the left hemisphere and 58% due to stroke. The incidence of aphasia was 70%; dysarthria and apraxia, 6%; functional alterations in communication, 17%; and 7% were normal. Statistically significant differences appeared when comparing the subgroup to controls in the Token Test.

CONCLUSIONS

We believe that this sample contributes to a better understanding of neurological patients with speech and language disturbances and may be useful as a reference for health professionals involved in the rehabilitation of such disorders.

Memory and aphasia

Sixty-one acute and 17 chronic vascular left-hemisphere damaged patients were tested with five memory tasks that investigated verbal short-term (digit span) and long-term (paired-associate and story learning) memory, and spatial short- and long-term memory (Corsi's span and learning). Both brain-damaged groups were significantly impaired in all memory tasks (except for chronic patients in the story learning task) compared to normal controls. The presence of aphasia and locus of lesion (anterior, posterior and deep) had no effect on the memory impairment, with only one exception of paired-associate learning that was better performed by non-aphasic than aphasic patients. Eleven subjects were better at paired-associate learning than story recall, the reverse dissociation was never found. Finally, chronic patients performed significantly better than acute patients only in the Corsi's learning task.