The Role of Processing Speed and Cognitive Control on Word Retrieval in Aging and Aphasia

Do age and language impairment affect speed of recognition for words with high and low closeness centrality within the phonological network?

PURPOSE

Speed and accuracy of lexical access change with healthy ageing and neurodegeneration. While a word's immediate phonological neighbourhood density (i.e. words differing by a single phoneme) influences access, connectivity to all words in the phonological network (i.e. closeness centrality) may influence processing. This study aimed to investigate the effect of closeness centrality on speed and accuracy of lexical processing pre- and post- a single word-training session in healthy younger and older adults, and adults with logopenic primary progressive aphasia (lvPPA), which affects phonological processing.

METHOD

Participants included 29 young and 17 older healthy controls, and 10 adults with lvPPA. Participants received one session of word-training on words with high or low closeness centrality, using a picture-word verification task. Changes in lexical decision reaction times (RT) and accuracy were measured.

RESULT

Baseline RT was unaffected by age and accuracy was at ceiling for controls. Post-training, only young adults' RT were significantly faster. Adults with lvPPA were slower and less accurate than controls at baseline, with no training effect. Closeness centrality did not influence performance.

CONCLUSION

Absence of training effect for older adults suggests higher threshold to induce priming, possibly associated with insufficient dosage or fatigue. Implications for word-finding interventions with older adults are discussed.

Semantic impairment in aphasia: A problem of control?

PURPOSE

The relationship between cognitive processes and language ability in aphasia has recently gained increasing attention, with some authors suggesting that control impairments may underlie difficulties with semantic tasks in aphasia. This paper aims to present an overview of the current research on the involvement of cognitive processes in semantic processing tasks and discuss the proposed relationship between cognitive control and semantic processing in aphasia.

METHOD

The role of cognitive processes in semantic processing tasks commonly used in the aphasiology literature is discussed and two theoretical approaches to semantic processing that contribute to the understanding of the nature of semantic breakdown in aphasia are outlined. Finally, we examine the evidence put forward in the Controlled Semantic Cognition framework with regard to the interpretation of impaired performance on semantic processing tasks in people with aphasia.

RESULT

Non-linguistic cognitive abilities such as working memory, inhibition and control are required by semantic processing tasks, in addition to access to conceptual information, making it difficult to dissociate these abilities. Several issues exist regarding the evidence put forward for a control deficit as the underlying cause of poor performance on semantic processing tasks in aphasia.

CONCLUSION

It remains unclear whether impairment on semantic tasks in people with aphasia is related to problems with the representation and/or processing (activation/retrieval) of meaning or problems with cognitive control (or both). Further research is still needed to fully understand how non-linguistic cognitive processes interact with semantic processing, as well as clarify and consistency the definition of control.

Correlating Eye-Tracking Fixation Metrics and Neuropsychological Assessment after Ischemic Stroke

Background and Objectives: Stroke survivors commonly experience cognitive deficits, which significantly impact their quality of life. Integrating modern technologies like eye tracking into cognitive assessments can provide objective and non-intrusive measurements. Materials and Methods: This study aimed to evaluate the cognitive and visual processing capabilities of stroke patients using eye-tracking metrics and psychological evaluations. A cohort of 84 ischemic stroke patients from the N-PEP-12 clinical study was selected for secondary analysis, based on the availability of eye-tracking data collected during a visual search task using an adapted Trail Making Test. Standardized cognitive assessments, including the Montreal Cognitive Assessment (MoCA) and digit span tasks, were also conducted. Results: Correlation analyses revealed some notable relationships between eye-tracking metrics and cognitive measures, such as a positive correlation between Symbol Search performance and the number of fixations. Anxiety levels were found to be positively correlated with first fixation duration, while longer first fixation durations were associated with poorer cognitive performance. However, most correlations were not statistically significant. Nonparametric ANOVA showed no significant differences in fixation metrics across the visits. Conclusions: These findings suggest a complex relationship between cognitive status, gaze fixation behavior, and psychological well-being in stroke patients. Further research with larger sample sizes and analysis of saccadic eye movements is needed to better understand these relationships and inform effective interventions for stroke rehabilitation.

Acoustic and phonemic processing are impaired in individuals with aphasia

Acoustic and phonemic processing are understudied in aphasia, a language disorder that can affect different levels and modalities of language processing. For successful speech comprehension, processing of the speech envelope is necessary, which relates to amplitude changes over time (e.g., the rise times). Moreover, to identify speech sounds (i.e., phonemes), efficient processing of spectro-temporal changes as reflected in formant transitions is essential. Given the underrepresentation of aphasia studies on these aspects, we tested rise time processing and phoneme identification in 29 individuals with post-stroke aphasia and 23 healthy age-matched controls. We found significantly lower performance in the aphasia group than in the control group on both tasks, even when controlling for individual differences in hearing levels and cognitive functioning. Further, by conducting an individual deviance analysis, we found a low-level acoustic or phonemic processing impairment in 76% of individuals with aphasia. Additionally, we investigated whether this impairment would propagate to higher-level language processing and found that rise time processing predicts phonological processing performance in individuals with aphasia. These findings show that it is important to develop diagnostic and treatment tools that target low-level language processing mechanisms.

Descriptive discourse in fluent aphasia: The predictive role of attention, phonology, lexical retrieval and semantics

AIMS

To study the relationship between cognitive and linguistic skills (as measured through standardized tasks) over spontaneous speech elicited during a picture description task.

METHODS & PROCEDURES

21 controls and 19 people with fluent aphasia matched by age and sex were evaluated using transcripts made from a picture description task coded using the CHAT format and analyzed using Computerized Language Analysis (CLAN). Indices obtained from the speech samples contained measures of lexical quantity and diversity, morphosyntactic complexity, informativeness, and speech fluency, along with different kinds of speech errors. We studied their correlations with attentional measures from Conners' Continuous Performance Test and with standardized measures of naming, pseudoword repetition and semantic non-verbal association. We further used stepwise linear regression to analyze the predictive value of standardized linguistic and cognitive skills over discursive indices.

OUTCOMES & RESULTS

Contrary to our initial hypothesis, there were no significant correlations between attentional scores and discourse variables in aphasic participants. Moreover, semantic association, along with naming, was the measure more related with discourse performance in people with fluent aphasia, but cognitive and linguistic standardized measures had overall little predictive power on most discourse indices. In the control group, there was a certain association of naming skills and attentional reaction time with discourse variables, but their predictive power was also low.

CONCLUSIONS & IMPLICATIONS

The current results do not support a strong relationship between basic attentional skills and performance in descriptive discourse in fluent aphasia. Although some of the standardized tasks seem to bear some relationship with spontaneous speech, there is a high amount of interindividual variability in discourse that is not captured by classical cognitive tasks routinely used in assessment. Further work on the determinants of discourse performance in aphasia and on the clinical application of discourse analysis is warranted.

Which blueberries are better value? The development and validation of the functional numeracy assessment for adults with aphasia

BACKGROUND

People with aphasia (PWA) can experience functional numeracy difficulties, that is, problems understanding or using numbers in everyday life, which can have numerous negative impacts on their daily lives. There is growing interest in designing functional numeracy interventions for PWA; however, there are limited suitable assessments available to monitor the impact of these interventions. Existing functional numeracy assessments lack breadth and are not designed to be accessible for PWA, potentially confounding their performance. Additionally, they do not include real-life demands, such as time pressure, which may affect their ecological validity. Thus, there is a crucial need for a new assessment to facilitate further research of PWA's functional numeracy.

AIMS

To develop, validate and pilot a wide-ranging, aphasia-friendly functional numeracy assessment to investigate how functional numeracy is impacted by aphasia severity and time pressure demands, and to explore predictors of PWA's functional numeracy.

METHODS & PROCEDURES

To develop the Functional Numeracy Assessment (FNA), 38 items inspired by the General Health Numeracy Test (GHNT) and Excellence Gateway were adapted for suitability for PWA and entered in a computerized psychometric-style test. The final 23 items (FNA23) were selected based on 213 neurotypical controls' performance, and controlled for difficulty, response modality and required numeracy skills. Aphasia-friendly adaptations of the GHNT and Subjective Numeracy Scale were used to examine the FNA23's concurrent validity. Internal consistency reliability and interrater reliability (for spoken responses) were also examined. A novel Time Pressure Task was created by slight adaptation of seven FNA23 questions to explore the effects of time pressure on functional numeracy performance. A total of 20 PWA and 102 controls completed all measures on an online testing platform.

OUTCOMES & RESULTS

The FNA23 demonstrated acceptable internal consistency reliability (KR-20 = 0.81) and perfect interrater reliability (for spoken responses). FNA23 and GHNT scores were positively associated, suggesting satisfactory concurrent validity. PWA demonstrated poorer functional numeracy than controls and took longer to complete assessments, indicating that aphasia impacts functional numeracy. Time pressure did not significantly impact performance. PWA demonstrated a wide range of functional numeracy abilities, with some performing similarly to controls.

CONCLUSIONS & IMPLICATIONS

The FNA23 is a wide-ranging, valid and reliable assessment which, with further development, will be a useful tool to identify and monitor PWA's functional numeracy difficulties in research and clinical practice. Considering PWA's widespread functional numeracy difficulties evidenced by this study, all PWA would likely benefit from routine evaluation for functional numeracy difficulties as part of their neurorehabilitation journeys.

WHAT THIS PAPER ADDS

What is already known on this subject Few studies have investigated functional numeracy difficulties in PWA. No published functional numeracy assessments exist that have been specifically designed to be accessible for PWA. What this paper adds to existing knowledge The newly developed FNA23 is a valid and reliable tool to extensively assess PWA's functional numeracy. This study confirmed previous findings of widespread functional numeracy difficulties in PWA that are related to their aphasia severity. What are the potential or actual clinical implications of this work? The FNA23 can be used to assess PWA's functional numeracy to inform areas of strengths and difficulties to target in intervention, and to monitor progress towards achieving intervention objectives. All PWA should be routinely evaluated for functional numeracy difficulties.

Dissociable language and executive control deficits and recovery in post-stroke aphasia: An exploratory observational and case series study

A growing body of evidence indicates many, but not all, individuals with post-stroke aphasia experience executive dysfunction. Relationships between language and executive function skills are often reported in the literature, but the degree of interdependence between these abilities remains largely unanswered. Therefore, in this study, we investigated the extent to which language and executive control deficits dissociated in 1) acute stroke and 2) longitudinal aphasia recovery. Twenty-three individuals admitted to Johns Hopkins Hospital with a new left hemisphere stroke completed the Western Aphasia Battery-Revised (WAB-R), several additional language measures (of naming, semantics, spontaneous speech, and oral reading), and three non-linguistic cognitive tasks from the NIH Toolbox (i.e., Pattern Comparison Processing Speed Test, Flanker Inhibitory Control and Attention Test, and Dimensional Change Card Sorting Test). Two participants with aphasia (PWA) with temporoparietal lesions, one of whom (PWA1) had greater temporal but less frontal and superior parietal damage than the other (PWA2), also completed testing at subacute (three months post-onset) and early chronic (six months post-onset) time points. In aim 1, principal component analysis on the acute test data (excluding the WAB-R) revealed language and non-linguistic executive control tasks largely loaded onto separate components. Both components were significant predictors of acute aphasia severity per the WAB-R Aphasia Quotient (AQ). Crucially, executive dysfunction explained an additional 17% of the variance in AQ beyond the explanatory power of language impairments alone. In aim 2, both case patients exhibited language and executive control deficits at the acute post-stroke stage. A dissociation was observed in longitudinal recovery of these patients. By the early chronic time point, PWA1 exhibited improved (but persistent) deficits in several language domains and recovered executive control. In contrast, PWA2 demonstrated mostly recovered language but persistent executive dysfunction. Greater damage to language and attention networks in these respective patients may explain the observed behavioral patterns. These results demonstrate that language and executive control can dissociate (at least to a degree), but both contribute to early post-stroke presentation of aphasia and likely influence longitudinal 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.

Processing Speed Predicts Mean Performance in Task-Switching but Not Task-Switching Cost

In several studies, it has been suggested that task-switching performance is linked to processing speed. Here we argue that the relation between processing speed and high-level cognitive ability found in previous studies may be due to confounded measurements of processing speed and task-switching ability. In the present study we required participants to complete an inspection time (IT) task to probe their processing speed. We employed conventional task-switching paradigms but applied a linear integrated speed-accuracy score (LISAS) which combines latency and accuracy scores to express task-switching ability. The results of regression analyses show that IT predicted average performance in task-switching paradigms. However, IT did not relate to any specific effects common in the task-switching task, which contradicts previous results. Our results suggest independent mechanisms of processing speed and tasks that require a high level of cognitive flexibility and control.

What is Functional Communication? A Theoretical Framework for Real-World Communication Applied to Aphasia Rehabilitation

Aphasia is an impairment of language caused by acquired brain damage such as stroke or traumatic brain injury, that affects a person’s ability to communicate effectively. The aim of rehabilitation in aphasia is to improve everyday communication, improving an individual’s ability to function in their day-to-day life. For that reason, a thorough understanding of naturalistic communication and its underlying mechanisms is imperative. The field of aphasiology currently lacks an agreed, comprehensive, theoretically founded definition of communication. Instead, multiple disparate interpretations of functional communication are used. We argue that this makes it nearly impossible to validly and reliably assess a person’s communicative performance, to target this behaviour through therapy, and to measure improvements post-therapy. In this article we propose a structured, theoretical approach to defining the concept of functional communication. We argue for a view of communication as “situated language use”, borrowed from empirical psycholinguistic studies with non-brain damaged adults. This framework defines language use as: (1) interactive, (2) multimodal, and (3) contextual. Existing research on each component of the framework from non-brain damaged adults and people with aphasia is reviewed. The consequences of adopting this approach to assessment and therapy for aphasia rehabilitation are discussed. The aim of this article is to encourage a more systematic, comprehensive approach to the study and treatment of situated language use in aphasia.