Prism adaptation in Alzheimer's and Huntington's disease.

13 Ss with Alzheimer's disease (AD), 14 with Huntington's disease (HD), and 16 normal elderly control Ss were compared on a perceptual adaptation task involving laterally displaced vision. All Ss were required to point to a target while wearing distorting prisms that shifted objects 20° to the right or left. Quantitative indices of baseline, preadaptation, adaptation, and aftereffects were obtained. Only HD patients failed to adapt to the prisms after visuomotor feedback and to evidence negative aftereffects when the prisms were removed. Adaptation was significantly correlated with dementia for HD patients (r?=?–.63, p?r?=?–.13, p?