Unraveling the Thread of Aphasia Rehabilitation: A Translational Cognitive Perspective

Translational neuroscience is a multidisciplinary field that aims to bridge the gap between basic science and clinical practice. Regarding aphasia rehabilitation, there are still several unresolved issues related to the neural mechanisms that optimize language treatment. Although there are studies providing indications toward a translational approach to the remediation of acquired language disorders, the incorporation of fundamental neuroplasticity principles into this field is still in progress. From that aspect, in this narrative review, we discuss some key neuroplasticity principles, which have been elucidated through animal studies and which could eventually be applied in the context of aphasia treatment. This translational approach could be further strengthened by the implementation of intervention strategies that incorporate the idea that language is supported by domain-general mechanisms, which highlights the impact of non-linguistic factors in post-stroke language recovery. Here, we highlight that translational research in aphasia has the potential to advance our knowledge of brain-language relationships. We further argue that advances in this field could lead to improvement in the remediation of acquired language disturbances by remodeling the rationale of aphasia-therapy approaches. Arguably, the complex anatomy and phenomenology of aphasia dictate the need for a multidisciplinary approach with one of its main pillars being translational research.

Short-term memory and sentence comprehension in Catalan aphasia

The main goal of the present study is to investigate visual and verbal short-term memory side to side with sentence comprehension in Catalan-speaking subjects with aphasia in comparison with subjects without brain damage. We aim to examine whether there are any significant correlations between their performance on short-term memory and comprehension tasks in order to evaluate the hypothesis that linguistic and memory deficits in aphasia are the result of a dysfunction of a common mechanism, usually short-term memory. Eigthy-four control subjects and twelve individuals suffering from different types of aphasia were assessed using the Catalan version of the Comprehensive Aphasia Test (CAT-CAT), which includes one recognition task and two digit and word span tests to evaluate visual and verbal short-term memory, respectively, as well as a sentence-to-picture comprehension task. The results showed that the performance of subjects with aphasia was significantly low on all tasks. Yet, the logistic regression analysis revealed that the magnitude of the differences between the control and experimental group varied across subtests, and that visual short-term memory was better preserved than verbal memory. The results also showed that there were no significant correlations between memory and language comprehension, which rules out the hypothesis that the deficits observed are due to a common underlying mechanism. Individual variation was also observed, specially on memory subtests, which suggest that memory impairments cannot explain the comprehension deficit in aphasia.

Predictors beyond the lesion: Health and demographic factors associated with aphasia severity

BACKGROUND

Lesion-related factors are associated with severity of language impairment in persons with aphasia. The extent to which demographic and health factors predict language impairment beyond traditional cortical measures remains unknown. Identifying and understanding the contributions of factors to predictive models of severity constitutes critical knowledge for clinicians interested in charting the likely course of aphasia in their patients and designing effective treatment approaches in light of those predictions.

METHODS

Utilizing neuroimaging and language testing from our cohort of 224 individuals in the chronic stage of recovery from a left-hemisphere stroke in a cross-sectional study, we first conducted a lesion symptom mapping (LSM) analysis to identify regions associated with aphasia severity scores. After controlling for lesion volume and damage to pre-identified areas, three models were created to predict severity scores: 1) Demographic Model (N = 147); 2) Health Model (N = 106); and 3) Overall Model (N = 106). Finally, all identified factors were entered into a Final Model to predict raw severity scores.

RESULTS

Two areas were associated with aphasia severity-left posterior insula and left arcuate fasciculus. The results from the Demographic Model revealed non-linguistic cognitive ability, age at stroke, and time post-stroke as significant predictors of severity (P = .005; P = .02; P = .001, respectively), and results from the Health Model suggested the extent of leukoaraiosis is associated with severity (P = .0004). The Overall Model showed a relationship between aphasia severity and cognitive ability (P = .01), time post-stroke (P = .002), and leukoaraiosis (P = .01). In the Final Model, which aimed to predict raw severity scores, demographic, health, and lesion factors explained 55% of the variance in severity, with health and demographic factors uniquely explaining nearly half of performance variance.

CONCLUSIONS

Results from this study add to the literature suggesting patient-specific variables can shed light on individual differences in severity beyond lesion factors. Additionally, our results emphasize the importance of non-linguistic cognitive ability and brain health in aphasia recovery.

Executive control deficits and lesion correlates in acute left hemisphere stroke survivors with and without aphasia

In contrast to the traditional definition of the disorder, many individuals with aphasia exhibit non-linguistic cognitive impairments, including executive control deficits. Classic lesion studies cite frontal lobe damage in executive dysfunction, but more recent lesion symptom-mapping studies in chronic aphasia present mixed results. In this study, we compared executive control abilities of acute stroke survivors with and without aphasia and investigated lesion correlates of linguistic and non-linguistic cognitive tasks. Twenty-nine participants with acute left hemisphere stroke resulting in aphasia (n = 14) or no aphasia (n = 15) completed clinical MRI and testing, including three NIH Toolbox Cognition Batteries (Pattern Comparison Processing Speed, Flanker Inhibitory Control and Attention, and Dimensional Change Card Sort Tests) and the Boston Naming Test. We compared performance between groups using Wilcoxon rank sum tests. We used Least Absolute Shrinkage and Selection Operator Regression to identify neural markers (percent regional damage, hypoperfusion within vascular territories, and total lesion volume) of executive control deficits and anomia. Group performance was comparable on the Pattern Comparison Processing Speed Test, but people with aphasia had poorer standard scores, lower accuracy, and slower response times on the Dimensional Change Card Sort Test than people without aphasia. Damage to extrasylvian regions (dorsolateral prefrontal cortex, intraparietal sulcus) was related to executive control deficits, whereas language network damage (to inferior frontal and superior and posterior middle temporal gyri) was linked to naming impairments. These results suggest people with aphasia can exhibit comorbid executive control impairments linked to damage outside classic language network areas.

The Role of Gesture in Communication and Cognition: Implications for Understanding and Treating Neurogenic Communication Disorders

When people talk, they gesture. Gesture is a fundamental component of language that contributes meaningful and unique information to a spoken message and reflects the speaker's underlying knowledge and experiences. Theoretical perspectives of speech and gesture propose that they share a common conceptual origin and have a tightly integrated relationship, overlapping in time, meaning, and function to enrich the communicative context. We review a robust literature from the field of psychology documenting the benefits of gesture for communication for both speakers and listeners, as well as its important cognitive functions for organizing spoken language, and facilitating problem-solving, learning, and memory. Despite this evidence, gesture has been relatively understudied in populations with neurogenic communication disorders. While few studies have examined the rehabilitative potential of gesture in these populations, others have ignored gesture entirely or even discouraged its use. We review the literature characterizing gesture production and its role in intervention for people with aphasia, as well as describe the much sparser literature on gesture in cognitive communication disorders including right hemisphere damage, traumatic brain injury, and Alzheimer's disease. The neuroanatomical and behavioral profiles of these patient populations provide a unique opportunity to test theories of the relationship of speech and gesture and advance our understanding of their neural correlates. This review highlights several gaps in the field of communication disorders which may serve as a bridge for applying the psychological literature of gesture to the study of language disorders. Such future work would benefit from considering theoretical perspectives of gesture and using more rigorous and quantitative empirical methods in its approaches. We discuss implications for leveraging gesture to explore its untapped potential in understanding and rehabilitating neurogenic communication disorders.

Changes in white matter microstructure related to non-linguistic cognitive impairment in post-stroke aphasia

OBJECTS

Post-stroke aphasia (PSA) often have non-linguistic cognitive impairment. We aimed to ascertain its characteristics of non-linguistic cognitive impairment and the corresponding changes in white matter microstructures.

METHODS

Ten patients with PSA and 17 healthy controls (HCs) were enrolled. Loewenstein occupational therapy cognitive assessment (LOTCA) were used to assess non-linguistic cognitive function. Summary T-test was performed to compare the LOTCA scores between PSA and the Chinese norm. Tract-based spatial statistics (TBSS) was used to calculate fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD) after collecting diffusion tensor imaging data. Correlation analysis was performed between these metrics and LOTCA scores.

RESULTS

The days after stroke onset of PSA was 428.0±52.0. The total LOTCA score of PSA (78.20±22.63) was lower than the Chinese norm (97.65±16.24, P=0.003), as well as the scores of orientation, spatial perception (SP), motor praxis (MP), and attention (P<0.05). Lower FA and higher MD/RD in bilateral inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), and left superior longitudinal fasciculus (SLF) were found in PSA compared with HCs. The MD and RD of the right uncinate fasciculus (UF) was negatively correlated with SP and MP scores (r=-0.787, r=-0.733, r=-0.726; P<0.05). The FA of left UF was negatively correlated with orientation score (r=-0.690, P=0.04).

CONCLUSION

Patients with PSA have non-linguistic cognitive impairment. The integrity of the white matter microstructures can be extensively damaged. Impaired SP and MP in patients with PSA are related to UF damage.

Post-stroke Aphasia as a Prognostic Factor for Cognitive and Functional Changes in Patients With Stroke: Ischemic Versus Hemorrhagic

Objective

To investigate the comprehensive outcomes in aphasic patients, including their cognitive and functional status after ischemic or hemorrhagic stroke. It also aimed to clarify whether aphasia is a prognostic factor for cognitive and functional improvements in stroke patients.

Methods

Sixty-seven ischemic or hemorrhagic stroke patients in the subacute stage who had been diagnosed with aphasia using the Korean version of Frenchay Aphasia Screening Test (K-FAST) were included in the study. Forty-six stroke patients without aphasia were used as controls. All patients were examined with the Korean version of the Western Aphasia Battery (K-WAB). Cognitive and functional assessments of the patients including the Korean version of Mini-Mental State Examination (K-MMSE), and the Korean version of Modified Barthel Index (K-MBI) were performed during admission and 4 weeks after the initial assessments.

Results

The initial and follow-up total K-MMSE and K-MBI scores were significantly lower in aphasic patients than in non-aphasic controls. The K-WAB scores highly correlated with the total K-MMSE scores at the follow-up stage in all aphasic stroke patients. The K-WAB scores moderately correlated with the follow-up scores of the K-MBI in ischemic stroke patients but not in hemorrhagic stroke patients.

Conclusion

Aphasia influences the cognitive and functional status of stroke patients and has a greater impact on cognitive improvement. Aphasia severity can be one of the prognostic factors for cognitive status in aphasic patients with stroke.

Decision Making by People With Aphasia: A Comparison of Linguistic and Nonlinguistic Measures

Purpose Decision making involves multiple cognitive and linguistic processes. The extent to which these processes are involved depends, in part, on the conditions under which decision making is assessed. Because people with aphasia (PWA) have impaired language abilities and may also present with cognitive deficits, they may have difficulty during decision-making tasks. Yet little research exists on the decision-making abilities of PWA. Thus, the purposes of this study were to investigate the performance of PWA on linguistic and nonlinguistic decision-making measures and to explore the relationship between decision making and cognitive test performance. Method A quasi-experimental design was used to compare the performance of PWA (n = 16) and age- and education-matched control participants (n = 16) on three decision-making tasks: Making a Decision subtest from the Functional Assessment of Verbal Reasoning and Executive Strategies (linguistic decision-making task), Iowa Gambling Task (nonlinguistic decision-making task with ambiguity), and Game of Dice Task (nonlinguistic decision-making task without ambiguity). Participants also completed assessments of language, working memory, and executive functions. Scores on the three decision-making tasks were compared between groups, and cognitive influences on decision-making performance were examined using correlation analyses. Results PWA differed significantly from control participants on linguistic decision making, particularly when required to verbalize their rationale for making their decision. PWA and control participants did not differ significantly on measures of nonlinguistic decision making. Performance on multiple cognitive measures was correlated with performance on the linguistic reasoning task, as well as one of the nonlinguistic tasks (Game of Dice Task). Conclusions Decision-making tasks that are heavily dependent on language, such as those used in capacity assessments, may disadvantage PWA. Assessments of decision-making capacity should include communication supports for people with acquired communication disorders; further investigation in the areas of decision making and aphasia is needed.

Language in schizophrenia and aphasia: the relationship with non-verbal cognition and thought disorder

Objective: To determine the relationship between language abnormalities and broader cognitive impairment and thought disorder by examining language and cognition in schizophrenia and aphasia (a primary language disorder).Methods: Cognitive and linguistic profiles were measured with a battery of standardised tests, and compared in a clinical population of n = 50 (n = 30 with schizophrenia and n = 20 with aphasia) and n = 61 non-clinical comparisons (n = 45 healthy controls and n = 16 non-affected first-degree relatives of patients with schizophrenia).Results: Both clinical groups showed linguistic deficits. Verbal impairment was more severe in participants with aphasia, whereas non-verbal performance was more affected in participants with schizophrenia. In schizophrenia, but not in aphasia, verbal and non-verbal performance were associated. Formal thought disorder was associated with impairment in executive function and in grammatical, but not naming, tasks.Conclusion: While patients with schizophrenia and aphasia showed language impairments, the nature and cognitive basis of these impairments may be different; language performance disassociates from broader cognitive functioning in aphasia but may be an intrinsic expression of a broader cognitive impairment in schizophrenia. Thought disorder may represent a core malfunction of grammatical processing. Results suggests that communicative ability may be a valid target in cognitive remediation strategies in schizophrenia.

Executive control in frontal lesion aphasia: Does verbal load matter?

Executive control impairments in aphasia resulting from frontal lesions are expected, given that integrity of frontal regions is critical to executive control task performance. Yet the consistency of executive control impairments in aphasia is poorly understood. This is due to previous studies using only a brief set of measures or failing to account for the high language processing demands of many executive control tasks. This study investigated performance across a series of specific and broad executive control task, whilst comparing differences between low or high verbal task versions. Ten participants with aphasia secondary to left inferior frontal lesions and fifteen age matched controls completed a battery of verbal and low verbal executive control tasks tapping into the three core domains of inhibiting, switching, and updating of working memory. For both controls and participants with aphasia, there was no consistent influence of verbal load on either reaction time or accuracy performance. When compared to controls, participants with aphasia demonstrate a general slowing of responses across all reaction time tasks, and are less accurate on switching and updating tasks. These findings do suggest that language processing is not essential for executive control task performance, given that verbal load does not matter. Furthermore, tasks which involve holding multiple sources of information in mind, such as during switching or updating, are particularly vulnerable in aphasia.

Cognitive functioning in chronic post-stroke aphasia

There is a minimal amount of knowledge regarding the cognitive abilities of people with aphasia. We evaluated the performance of individuals with chronic aphasia (AP) and control participants without aphasia (CP) with left hemisphere stroke in a battery of nonverbal cognitive tests and its relationship with aphasia severity, comprehension abilities, and speech fluency in a prospective cross-sectional study. Cognitive evaluation comprised 10 nonverbal tests. Scores were converted to age and education adjusted standard scores. Forty-eight AP and 32 CP were included. AP average scores were below normal range in three tests: Camel and Cactus Test, immediate recall of 5 Objects Test and Spatial Span. The mean test scores were significantly lower in AP than in CP, except in four tests. Aphasia severity and verbal comprehension ability correlated significantly with semantic memory, constructive abilities and attention/processing speed tests. Subjects with nonfluent aphasia had lower scores than CP in memory, executive functions and attention tests, while subjects with fluent aphasia showed lower scores in memory tests only. On average half of the individuals with aphasia exhibit results within the normal range. Nonetheless, their performance was worse than that of controls, despite the fact that many tests do not correlate with the severity of language disorder.

Different Cognitive Profiles of Patients with Severe Aphasia

Cognitive dysfunction frequently occurs in aphasic patients and primarily compromises linguistic skills. However, patients suffering from severe aphasia show heterogeneous performance in basic cognition. Our aim was to characterize the cognitive profiles of patients with severe aphasia and to determine whether they also differ as to residual linguistic abilities. We examined 189 patients with severe aphasia with standard language tests and with the CoBaGA (Cognitive Test Battery for Global Aphasia), a battery of nonverbal tests that assesses a wide range of cognitive domains such as attention, executive functions, intelligence, memory, visual-auditory recognition, and visual-spatial abilities. Twenty patients were also followed longitudinally in order to assess their improvement in cognitive skills after speech therapy. Three different subgroups of patients with different types and severity of cognitive impairment were evidenced. Subgroups differed as to residual linguistic skills, in particular comprehension and reading-writing abilities. Attention, reasoning, and executive functions improved after language rehabilitation. This study highlights the importance of an extensive evaluation of cognitive functions in patients with severe aphasia.