Assessment of linguistic and verbal short-term memory components of language abilities in aphasia.

Some current models of aphasia emphasize a role of short-term memory in the processing of language and propose that the language impairment in aphasia involves impairment to cognitive processes that activate and maintain representations of words over the time-period needed to support single word and multiple word tasks, including verbal span tasks. This paper reports normative data from 39 people with aphasia and 16 age-matched neurotypical controls on a test battery for aphasia that assesses effects of increased short-term/working memory load on word and sentence processing as well as effects of linguistic variations on verbal short-term memory abilities Two concepts are discussed that capture the unique potential of this test battery for research and clinical practice: specificity of diagnosis and sensitivity to all degrees of aphasia severity, including mild aphasia. An analysis is included that shows how the performance of individuals with mild aphasia who achieve normal level of performance on the Western Aphasia Battery (Kertesz, 2006) show a decline in a temporal delay condition that is greater than performance of control participants. We also report preliminary data showing differential effects of adding a time interval before a response or between items to be compared: reduced accuracy for some individuals with aphasia and improved accuracy for others. The theoretical and clinical importance of this finding is discussed, as well as the overall potential for this test battery to be used in research and as a clinical tool. Finally, we discuss the relevance of this test battery to investigate functional communication abilities in aphasia.

Effects of semantic context on access to words of low imageability in deep-phonological dysphasia: a treatment case study.

BACKGROUND: Deep dysphasia is a relatively rare subcategory of aphasia, characterised by word repetition impairment and a profound auditory-verbal short-term memory (STM) limitation. Repetition of words is better than nonwords (lexicality effect) and better for high-image than low-image words (imageability effect). Another related language impairment profile is phonological dysphasia, which includes all of the characteristics of deep dysphasia except for the occurrence of semantic errors in single word repetition. The overlap in symptoms of deep and phonological dysphasia has led to the hypothesis that they share the same root cause, impaired maintenance of activated representation of words, but that they differ in severity of that impairment, with deep dysphasia being more severe. AIMS: We report a single-subject multiple baseline, multiple probe treatment study of a person who presented with a pattern of repetition that was consistent with the continuum of deep-phonological dysphasia: imageability and lexicality effects in repetition of single and multiple words and semantic errors in repetition of multiple-word utterances. The aim of this treatment study was to improve access to and repetition of low-imageability words by embedding them in modifier-noun phrases that enhanced their imageability. METHODS & PROCEDURES: The treatment involved repetition of abstract noun pairs. We created modifier-abstract noun phrases that increased the semantic and syntactic cohesiveness of the words in the pair. For example, the phrases "long distance" and "social exclusion" were developed to improve repetition of the abstract pair "distance-exclusion". The goal of this manipulation was to increase the probability of accessing lexical and semantic representations of abstract words in repetition by enriching their semantic -syntactic context. We predicted that this increase in accessibility would be maintained when the words were repeated as pairs, but without the contextual phrase. OUTCOMES & RESULTS: Treatment outcomes indicated that increasing the semantic and syntactic cohesiveness of low-imageability and low-frequency words later improved this participant's ability to repeat those words when presented in isolation. CONCLUSIONS: This treatment approach to improving access to abstract word pairs for repetition was successful for our participant with phonological dysphasia. The approach exemplifies the potential value in manipulating linguistic characteristics of stimuli in ways that improve access between phonological and lexical-semantic levels of representation. Additionally, this study demonstrates how principles of a cognitive model of word processing can be used to guide treatment of word processing impairments in aphasia.

Short-Term Memory and Aphasia: From Theory to Treatment.

This article reviews existing research on the interactions between verbal short-term memory and language processing impairments in aphasia. Theoretical models of short-term memory are reviewed, starting with a model assuming a separation between short-term memory and language, and progressing to models that view verbal short-term memory as a cognitive requirement of language processing. The review highlights a verbal short-term memory model derived from an interactive activation model of word retrieval. This model holds that verbal short-term memory encompasses the temporary activation of linguistic knowledge (e.g., semantic, lexical, and phonological features) during language production and comprehension tasks. Empirical evidence supporting this model, which views short-term memory in the context of the processes it subserves, is outlined. Studies that use a classic measure of verbal short-term memory (i.e., number of words/digits correctly recalled in immediate serial recall) as well as those that use more intricate measures (e.g., serial position effects in immediate serial recall) are discussed. Treatment research that uses verbal short-term memory tasks in an attempt to improve language processing is then summarized, with a particular focus on word retrieval. A discussion of the limitations of current research and possible future directions concludes the review.

Using Virtual Technology to Promote Functional Communication in Aphasia: Preliminary Evidence From Interactive Dialogues With Human and Virtual Clinicians.

PURPOSE: We investigated the feasibility of using a virtual clinician (VC) to promote functional communication abilities of persons with aphasia (PWAs). We aimed to determine whether the quantity and quality of verbal output in dialogues with a VC would be the same or greater than those with a human clinician (HC). METHOD: Four PWAs practiced dialogues for 2 sessions each with a HC and VC. Dialogues from before and after practice were transcribed and analyzed for content. We compared measures taken before and after practice in the VC and HC conditions. RESULTS: Results were mixed. Participants either produced more verbal output with the VC or showed no difference on this measure between the VC and HC conditions. Participants also showed some improvement in postpractice narratives. CONCLUSION: Results provide support for the feasibility and applicability of virtual technology to real-life communication contexts to improve functional communication in PWAs.

Effects of working memory load on processing of sounds and meanings of words in aphasia.

BACKGROUND: Language performance in aphasia can vary depending on several variables such as stimulus characteristics and task demands. This study focuses on the degree of verbal working memory (WM) load inherent in the language task and how this variable affects language performance by individuals with aphasia. AIMS: The first aim was to identify the effects of increased verbal WM load on the performance of judgments of semantic similarity (synonymy) and phonological similarity (rhyming). The second aim was to determine if any of the following abilities could modulate the verbal WM load effect: semantic or phonological access, semantic or phonological short-term memory (STM) and any of the following executive processing abilities: inhibition, verbal WM updating, and set shifting. METHOD AND PROCEDURES: Thirty-one individuals with aphasia and 11 controls participated in this study. They were administered a synonymy judgment task and a rhyming judgment task under high and low verbal WM load conditions that were compared to each other. In a second set of analyses, multiple regression was used to identify which factors (as noted above) modulated the verbal WM load effect. OUTCOME AND RESULTS: For participants with aphasia, increased verbal WM load significantly reduced accuracy of performance on synonymy and rhyming judgments. Better performance in the low verbal WM load conditions was evident even after correcting for chance. The synonymy task included concrete and abstract word triplets. When these were examined separately, the verbal WM load effect was significant for the abstract words, but not the concrete words. The same pattern was observed in the performance of the control participants. Additionally, the second set of analyses revealed that semantic STM and one executive function, inhibition ability, emerged as the strongest predictors of the verbal WM load effect in these judgment tasks for individuals with aphasia. CONCLUSIONS: The results of this study have important implications for diagnosis and treatment of aphasia. As the roles of verbal STM capacity, executive functions and verbal WM load in language processing are better understood, measurements of these variables can be incorporated into our diagnostic protocols. Moreover, if cognitive abilities such as STM and executive functions support language processing and their impairment adversely affects language function, treating them directly in the context of language tasks should translate into improved language function.

Lexicality Effects in Word and Nonword Recall of Semantic Dementia and Progressive Nonfluent Aphasia.

BACKGROUND: Verbal working memory is an essential component of many language functions, including sentence comprehension and word learning. As such, working memory has emerged as a domain of intense research interest both in aphasiology and in the broader field of cognitive neuroscience. The integrity of verbal working memory encoding relies on a fluid interaction between semantic and phonological processes. That is, we encode verbal detail using many cues related to both the sound and meaning of words. Lesion models can provide an effective means of parsing the contributions of phonological or semantic impairment to recall performance. METHODS AND PROCEDURES: We employed the lesion model approach here by contrasting the nature of lexicality errors incurred during recall of word and nonword sequences by 3individuals with progressive nonfluent aphasia (a phonological dominant impairment) compared to that of 2 individuals with semantic dementia (a semantic dominant impairment). We focused on psycholinguistic attributes of correctly recalled stimuli relative to those that elicited a lexicality error (i.e., nonword → word OR word → nonword). OUTCOMES AND RESULTS: Patients with semantic dementia showed greater sensitivity to phonological attributes (e.g., phoneme length, wordlikeness) of the target items relative to semantic attributes (e.g., familiarity). Patients with PNFA showed the opposite pattern, marked by sensitivity to word frequency, age of acquisition, familiarity, and imageability. CONCLUSIONS: We interpret these results in favor of a processing strategy such that in the context of a focal phonological impairment patients revert to an over-reliance on preserved semantic processing abilities. In contrast, a focal semantic impairment forces both reliance upon and hypersensitivity to phonological attributes of target words. We relate this interpretation to previous hypotheses about the nature of verbal short-term memory in progressive aphasia.

Remediation of language processing in aphasia: Improving activation and maintenance of linguistic representations in (verbal) short-term memory.

BACKGROUND: Verbal short-term memory (STM) impairments are invariably present in aphasia. Word processing involves a minimal form of verbal STM, i.e., the time course over which semantic and phonological representations are activated and maintained until they are comprehended, produced, or repeated. Thus it is reasonable that impairments of word processing and verbal STM may co-occur. The co-occurrence of language and STM impairments in aphasia has motivated an active area of research that has revealed much about the relationship of these two systems and the effect of their impairment on language function and verbal learning (Freedman & Martin, 2001; Martin & Saffran, 1999; Trojano & Grossi, 1995). In keeping with this view a number of researchers have developed treatment protocols to improve verbal STM in order to improve language function (e.g., Koenig-Bruhin & Studer-Eichenberger, 2007). This account of aphasia predicts that treatment of a fundamental ability, such as STM, which supports language function, should lead to improvements that generalise to content and tasks beyond those implemented in treatment. AIMS: We investigated the efficacy of a treatment for language impairment that targets two language support processes: verbal short-term memory (STM) and executive processing, in the context of a language task (repetition). We hypothesised that treatment of these abilities would improve repetition abilities and performance on other language tasks that require STM. METHOD: A single-participant, multiple-baseline, multiple-probe design across behaviours was used with a participant with conduction aphasia. The treatment involved repetition of words and nonwords under three "interval" conditions, which varied the time between hearing and repeating the stimulus. Measures of treatment effects included acquisition, maintenance, and follow-up data, effect sizes, and pre- and post-treatment performance on a test battery that varies the STM and executive function demands of language tasks. OUTCOMES #ENTITYSTARTX00026; RESULTS: Improvement of repetition was mostly specific to treated stimuli. Post-treatment measures of language ability indicated improvements in single and multiple word processing tasks, verbal working memory tasks, and verbal span. CONCLUSIONS: Treatment of STM and executive processes in the context of a word repetition task resulted in improvements in other non-treated language tasks. The approach used in this study can be incorporated into other language-processing tasks typically used in treatment of language disorders (e.g., sentence processing).

Effects of two lexical retrieval cueing treatments on action naming in aphasia.

The effects of two cueing treatments, Phonological Cueing Treatment (PCT) and Semantic Cueing Treatment (SCT), were examined with three chronic speakers with aphasia. The effects of treatment on action naming were measured with the use of single-subject experimental designs. The participants had received PCT and SCT to improve object naming in a previous investigation and had responded positively to both treatments. In the current study, Speaker 1 received SCT, Speaker 2 received PCT, and Speaker 3 received both SCT and PCT. Action naming improved for Speakers 1 and 3, but not for Speaker 2. These findings indicate that PCT and SCT may have utility in facilitating action naming for some speakers with aphasia but that the effects of these treatments may vary across grammatical form classes (e.g., nouns versus verbs).