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Poster B33, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

The neural representation of concrete and abstract verb processing in aphasia

Reem S. W. Alyahya1,2, Ajay Halai1, Paul Conroy1, Matthew A. Lambon Ralph1;1Neuroscience and Aphasia Research Unit, University of Manchester, United Kingdom, 2King Fahad Medical City, Saudi Arabia

Processing concrete concepts is easier and more efficient than processing abstract ones in healthy adults and people with language impairments following brain damage (aphasia). This concreteness effect led some researchers to propose segregated neural correlates to process concrete and abstract concepts. While, concreteness effects have only been documented in nouns, some studies have shown differences between processing nouns and verbs in aphasia. The aim of this study was to explore the behavioural status of concrete and abstract verb processing in aphasia, and identify their neural representation using lesion-symptom mapping. A review of the available neuropsychological and aphasiological tests suggested that there is a dearth of comprehension tests for abstract verbs. Therefore, we developed a neuropsychological test to assess the comprehension of concrete and abstract verbs. Specifically, we generated a new verb synonym judgement test that consists of 80 verb stimuli, in which we manipulated imageability and frequency values across and within conditions, yielding four categories: concrete high-frequency, concrete low-frequency, abstract high-frequency and abstract low-frequency. Normative data was collected from 25 elderly healthy participants and the results revealed ceiling effects across all four categories (> 97.2%). Subsequently, the test was administered to a cohort of 48 participants with chronic post-stroke aphasia, including a diverse range of aphasia classifications and severities. The results using a 2 x 2 ANOVA revealed a significant effect of imageability, with better comprehension of concrete verbs (Mean = 33.13, SD = 7.5) compared to abstract verbs (Mean = 23.64, SD =9.2). There was no effect of frequency or interaction effect between imageability and frequency on verb processing. This provides evidence that processing concrete verbs is more robust than abstract verbs in chronic post-stroke aphasia, which aligns with existing literature on concrete and abstract noun processing. Lesion-symptom mapping was conducted using voxel-based correlational methodology. The results revealed a range of common cortical regions that support processing concrete and abstract items in the left anterior temporal lobe and posterior supramarginal gyrus. Further direct contrast between concrete and abstract items revealed significant graded differences between them. Specifically, left frontal regions (inferior frontal gyrus, middle frontal gyrus and pre-central gyrus) were associated with processing abstract over concrete verbs; whereas, left posterior temporal and occipital regions (inferior temporal gyrus, posterior middle temporal gyrus and inferior lateral occipital cortex) were associated with processing concrete over abstract verbs. The current findings are consistent with results using other methods, such as functional neuroimaging and neuro-stimulation, proposing graded differences between the neural representation of concrete and abstract concepts. The contribution of left posterior ventral regions with concrete words probably reflects the activation of visual imagery associated with concrete concepts. On the other hand, the involvement of frontal regions with abstract words can be interpreted in terms of its role in semantic control, as a result of the variable meanings associated with abstract concepts, especially when the items is presented as a single word rather than a full context.

Topic Area: Language Disorders

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