Personal and extrapersonal orientation in Huntington's disease patients and those at risk

Two aspects of spatial cognition, personal and extrapersonal orientation, were studied in 21 patients with Huntington's disease, 49 individuals at risk for the disease, and 41 healthy control subjects. Personal orientation was assessed using the Standardized Road Map Test of Directional Sense. Extrapersonal orientation was measured using a route-walking task under two conditions--with and without turning the body while traversing the routes. Relative to normal controls, HD patients performed more slowly on the personal orientation test, and less accurately on the extrapersonal orientation task in the TURN, but not the NO-TURN condition. At-risk individuals performed like the normal control subjects on all measures. The results suggest a deficit in personal but not extrapersonal orientation in HD. It is suggested that disruption of fronto-striatal pathways mediates this deficit.