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Abstract
IntroductionPrevious literature has revealed that the anterior temporal lobe (ATL) is the semantic hub of left-sided or mixed semantic dementia (SD), whilst the semantic hub of right-sided SD has not been examined.MethodsSeventeen patients with right-sided SD, 18 patients with left-sided SD and 20 normal controls (NC) underwent neuropsychological assessments and magnetic resonance imaging scans. We investigated the relationship between the degree of cerebral atrophy in the whole brain and the severity of semantic deficits in left and right-sided SD samples, respectively.ResultsWe found the semantic deficits of right-sided SD patients were related to bilateral fusiform gyri and left temporal pole, whilst the left fusiform gyrus correlated with the semantic performance of left-sided SD patients. Moreover, all the findings couldn't be accounted for by total gray matter volume (GMV) or general cognitive degradation of patients.DiscussionThese results provide novel evidence for the current semantic theory, that the important regions for semantic processing include both anterior and posterior temporal lobes.
Highlights
Previous literature has revealed that the anterior temporal lobe (ATL) is the semantic hub of leftsided or mixed semantic dementia (SD), whilst the semantic hub of right-sided SD has not been examined
Using a large sample of mild and well-matched SD patients, we found left and right-sided SD patients had comparable deficits in semantic, episodic and general cognitive abilities and common atrophy in bilateral temporal and orbital frontal lobes
We found the left fusiform gyrus correlated with the semantic performance of left-sided SD, whilst the semantic deficits of right-sided SD patients were related to the bilateral fusiform gyri and left temporal pole
Summary
Semantic dementia (SD) is a variant of progressive primary aphasia which is characterized by the specific semantic loss and preserved abilities of other cognitive functions (Gorno-Tempini et al, 2011; Hodges and Patterson, 2007). Chan et al (2009) collected 20 right-sided SD patients and compared their imaging and neuropsychological data with left-sided SD patients. Right-sided SD patients suffer from severe semantic deficits. We applied comprehensive neuropsychological assessments and voxel-wised imaging scans in cases of mild right-sided SD and cases of mild left-sided SD with comparable severity. We assumed that (1) both groups would present with severe semantic deficits; (2) left-sided SD group would present with more severe language problems than rightsided SD group; (3) in right-sided SD sample, the semantic-related regions would include other regions such as the temporal pole beyond the fusiform gyrus. By using a big sample of right-sided SD patients, our study identifies their comprehensive characteristics and provides new evidence for the semantic model
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