Neuroanatomical correlations of visuospatial processing in primary progressive aphasia

Clinical phenotyping of primary progressive aphasia (PPA) has largely focused on speech and language presentations, leaving other cognitive domains under-examined. This study investigated the diagnostic utility of visuospatial profiles and examined their neural basis among the three main PPA variants. We studied the neuropsychological performances of 118 PPA participants and 30 cognitively normal controls, across eleven measures of visuospatial cognition, and investigated their neural correlates via voxel-based morphometry analysis using visuospatial composite scores derived from principal component analysis. Principal component analysis identified three main factors: visuospatial-executive, visuospatial-memory and visuomotor components. Logopenic variant PPA performed significantly worst across all components; nonfluent/agrammatic variant PPA showed deficits in the visuospatial-executive and visuomotor components compared to controls; and the semantic variant PPA scored significantly lower than nfvPPA and control in the visuospatial-memory component. Grey matter volumes over the right parieto-occipital cortices correlated with visuospatial-executive performance; volumetric changes in the right anterior parahippocampal gyrus and amygdala were associated with visuospatial-memory function, and visuomotor composite scores correlated significantly with the grey matter volume at the right precentral gyrus. Discriminant function analysis identified three visuospatial measures: Visual Object and Space Perception and Benson figure copy and recall test, classified 79.7% (94/118) of PPA into their specific variant. This study shows that each PPA variant also carries a distinctive visuospatial cognitive profile that corresponds with grey matter volumetric changes and in turn can be largely represented by their performance on the visuomotor, visuospatial memory and executive functions.