Evaluating the granularity and statistical structure of lesions and behaviour in post-stroke aphasia. Issue 2 (19th May 2020)

• Record Type: Journal Article
• Authors: Zhao, Ying; Halai, Ajay D; Lambon Ralph, Matthew A
• Is Part Of: Brain communications. Volume 2:Issue 2(2020)
• Publication Date: 2020-05-19
• Subjects: stroke -- aphasia -- lesion–symptom mapping -- middle cerebral artery -- cortical vascular branches; 616
• DOI: 10.1093/braincomms/fcaa062
• Languages: English
• ISSNs: 2632-1297

Abstract

Abstract: The pursuit of relating the location of neural damage to the pattern of acquired language and general cognitive deficits post-stroke stems back to the 19th century behavioural neurology. While spatial specificity has improved dramatically over time, from the large areas of damage specified by post-mortem investigation to the millimetre precision of modern MRI, there is an underlying issue that is rarely addressed, which relates to the fact that damage to a given area of the brain is not random but constrained by the brain's vasculature. Accordingly, the aim of this study was to uncover the statistical structure underlying the lesion profile in chronic aphasia post-stroke. By applying varimax-rotated principal component analysis to the lesions of 70 patients with chronic post-stroke aphasia, we identified 17 interpretable clusters, largely reflecting the vascular supply of middle cerebral artery sub-branches and other sources of individual variation in vascular supply as shown in classical angiography studies. This vascular parcellation produced smaller displacement error in simulated lesion–symptom analysis compared with individual voxels and Brodmann regions. A second principal component analysis of the patients' detailed neuropsychological data revealed a four-factor solution reflecting phonological, semantic, executive-demand and speech fluency abilities. As a preliminary exploration, stepwise regression was used to relate behavioural factor scores to the lesion principal components. Phonological ability was related to two components, which covered the posterior temporal region including the posterior segment of the arcuate fasciculus, and the inferior frontal gyrus. Three components were linked to semantic ability and were located in the white matter underlying the anterior temporal lobe, the supramarginal gyrus and angular gyrus. Executive-demand related to two components covering the dorsal edge of the middle cerebral artery territory, while speech fluency was linked to two components that were located in the middle frontal gyrus, precentral gyrus and subcortical regions (putamen and thalamus). Future studies can explore in formal terms the utility of these principal component analysis-derived lesion components for relating post-stroke lesions and symptoms. Abstract : Brain damage post-stroke is not random but is constrained by the neurovascular system. Zhao et al. applied principal component analysis to post-stroke lesions to construct a parcellation of the middle cerebral artery cortical supply. This parcellation was used in lesion–symptom mapping, and mis-localization analyses showed lower error compared to Brodmann areas. Graphical Abstract: