Prism Adaptation in Alzheimer's and Huntington's Disease

Abstract

Patients with Alzheimer's disease (AD; n = 13), Huntington's disease (HD; n = 14), and normal elderly control subjects (n = 16) were compared on a perceptual adaptation task involving laterally displaced vision. All subjects 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 < .01) but not for AD patients (r = -.13, p < .34). The impaired adaptation performance of HD patients, like previously demonstrated impairments in motor skill learning and weight biasing, seems to be due to a motor programming deficit resulting from neostriatal dysfunction.