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

Abstract

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.

Mismatch Negativity (MMN) as an Index of Cognitive Dysfunction

“…Lesions to cortical regions involving speech and language skills often result in significant deficits in communication ability, as well as deficits in related functions such as verbal working memory (Martin et al 2012). Investigations of auditory discrimination using the MMN in patients with acquired aphasia due to cerebral infarct have generally found reduced amplitude or absent MMNs to speech stimuli (Aaltonen et al 1993; Csépe et al 2001).…”

Accent identification by adults with aphasia

“…Note too that we did not find any relationship between level of language functioning and performance on our task (though this may have been due to the relatively small sample size). A second possible explanation for the difference in categorization ability is that the adults with aphasia may have diminished working memory capacity (Martin, Kohena, Kalinyak-Fliszara, Soverib, & Laineb, 2012), which would interfere with their ability to store the sentences whilst extracting perceptual cues and applying existing knowledge of accents before making a decision in the task. Research suggests that adults with aphasia require longer to process speech in an unfamiliar accent (Dunton et al, 2011) which may be due to greater demands on working memory.…”

Dual-Task Effects on Story Retell for Participants With Moderate, Mild, or No Aphasia: Quantitative and Qualitative Findings

“…Participants with aphasia completed a test battery to evaluate their language, verbal working memory, overall cognitive aptitude, and communication confidence. Tests included the Western Aphasia Battery Revised (WAB-R;Kertesz, 2006), the rhyming triplet judgment and synonym triplet judgment tasks from the Temple Assessment of Language and Short-term memory in Aphasia (TALSA; Martin, Kohen, & Kalinyak-Fliszar, 2010;Martin, Kohen, Kalinyak-Fliszar, Soveri, & Laine, 2012), the Test of Nonverbal Intelligence, Fourth Edition (TONI-IV;Brown, Sherbenou, & Johnson, 2010), and the Communication Confidence Rating Scale for Aphasia (CCRSA;Babbitt, Heinemann, Semik, & Cherney, 2011;Cherney, Babbitt, Semick, & Heinemann, 2011). All participants with aphasia were also screened for dysarthria, limb apraxia, and oral apraxia.…”