Brain Regions Underlying Repetition and Comprehension Deficits in Aphasia: Evidence from voxel-based lesion symptom mapping

Carly Mayberry (). Brain Regions Underlying Repetition and Comprehension Deficits in Aphasia: Evidence from voxel-based lesion symptom mapping Professional Doctorate, School of Psychology, The University of Queensland.

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Author Carly Mayberry
Thesis Title Brain Regions Underlying Repetition and Comprehension Deficits in Aphasia: Evidence from voxel-based lesion symptom mapping
School, Centre or Institute School of Psychology
Institution The University of Queensland
Thesis type Professional Doctorate
Total pages 124
Language eng
Subjects 179999 Psychology and Cognitive Sciences not elsewhere classified
Abstract/Summary Impairments in word repetition and comprehension are common in individuals with aphasia. Repetition deficits have traditionally been ascribed to a disconnection of a left hemisphere dorsal white matter pathway, the arcuate fascicle (Geschwind, 1965), whereas comprehension deficits have been attributed to lesions of the left temporal lobe (Turken & Dronkers, 2011). Voxelwise lesion symptom mapping (LSM) is a relatively new technique that tests the statistical significance of the relationship between behavioral performance and lesions delineated on brain images. Interestingly, recent LSM studies investigating the neural correlates of repetition deficits have implicated a gray matter region in the left temporoparietal junction (TPJ), rather than the arcuate fascicle (Baldo, Katseff, & Dronkers, 2011; Fridriksson et al., 2010). In addition, recent neuroimaging research has implicated a left hemisphere ventral white matter pathway, either the extreme capsule (Saur et al., 2008; Wong, Chandrasekaran, Garibaldi, & Wong, 2011) or the inferior occipito-frontal fascicle (de Zubicaray, Rose, & McMahon, 2011; Turken & Dronkers, 2011), in comprehension. The aim of the current study was to investigate the anatomical correlates of both repetition and comprehension, as assessed by the Western Aphasia Battery (WAB), a standardized clinical aphasia battery. Participants were 21 chronic stroke patients who had suffered a left hemisphere lesion. Participants suffered from a range of aphasic impairments at different levels of severity. Two WAB indices, repetition and comprehension, were used in the analyses. Residual scores for each index were also calculated by statistically covarying for the influence of each (e.g., Schwartz et al., 2011). Based on a priori hypotheses region-of-interest (ROI) LSM analyses were conducted. Our results confirmed that left TPJ lesions are associated with repetition deficits, although not with the arcuate fascicle, consistent with prior studies. Further, the results indicated that comprehension deficits were associated with lesions in the vicinity of the left posterior superior temporal gyrus/sulcus, with some additional involvement of the underlying white matter, although not with lesions to the extreme capsule or inferior occipito-frontal fascicle. These findings support the critical involvement of the TPJ region in repetition and the critical involvement of posterior superior temporal cortex in comprehension. Future studies of dorsal and ventral white matter pathways may benefit from employing Diffusion Tensor Imaging (DTI), an MRI technique that characterizes water molecule mobility and allows for more sensitive exploration of fibre tract integrity.
Keyword aphasia
voxelwise lesion-symptom mapping

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Created: Sat, 17 Nov 2012, 20:23:58 EST by Carly Mayberry on behalf of Faculty of Social & Behavioural Sciences