Disruption of estimation of body-scaled aperture width in Hemiparkinson's disease

A group of patients with left-sided symptoms of Parkinson's disease (LPD) w as compared with a group of patients with right-sided symptoms (RPD) and wi th a group of healthy age-matched controls on body-scaled judgements of ape rture width. Participants judged whether or not they would fit through a li fe-sized schematic doorway shown on a large screen. A staircase technique w as used to find the door width for which 50% of the judgements were positiv e. The ratio between this measure and the width of the participant's body a t the shoulders (the aperture to shoulder - A/S ratio) was calculated. The A/S ratio was approximately 1.5 in the LPD group, approximately 0.9 in the RPD group, and approximately 1. 1 in the control group, suggesting that the visual representation of the doorway (or that of its relationship to perce ived body-size) is compressed in LPD (and perhaps expanded in RPD). The A/S ratios were invariant with viewing distance (0.6 or 1.5 in), the contrast polarity of the display (white on dark, or vice versa) and the doorway surr ound (blank, or vertical or horizontal stripes). The findings are discussed with reference to the neural representation of external space and of the b ody, and to the motor problems of Parkinson's disease. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.