Cronin-Golomb A. Impact of optic flow perception and egocentric coordinates on veering

Spatial navigation is a complex process requiring integration of visuoperceptual information.The present study examined how visuospatial function relates to navigational veering in Parkinson’s disease, a movement disorder in which visuospatial cognition is affected by the degeneration of the basal ganglia and resulting dysfunction of the parietal lobes.We hypothesized that patients whose initial motor symptoms start on the left versus right side of the body (LPD, predominant right-hemisphere dysfunction; RPD, predominant left-hemisphere dysfunc-tion) would display distinct patterns of navigational veering associated with the groups ’ dissimilar visuospatial profiles. Of particular interest was to examine the association of navigational veering (lateral deviation along the medio-lateral axis) with perception of egocentric coordinates and of radial optic flow patterns, both of which are mediated by the parietal lobes. Thirty-one non-demented Parkinson’s disease patients (16 LPD, 15 RPD) and 18 healthy control (HC) adults received visuospatial tests, of whom 23 Parkinson’s disease patients and 17 HC also underwent veering assessment.The participants were examined on three visual-feedback navi-gation conditions: none (eyes closed), natural, and optic flow supplied by a virtual-reality headset. All groups veered to the left when walking with eyes closed, women with Parkinson’s disease more so than the other par-ticipants. On the navigation assessments with visual feedback, only LPD patients deviated right of centre. On tests of visuospatial function, the perceivedmidlinewas shifted rightward in LPD (men andwomen), increas