Reaction times and visuospatial processing in Parkinson's disease.

Three motor reaction time tasks which differed in visuospatial complexity but not in motor demands were completed by a group of Parkinson's disease patients and a group of matched control subjects. Response initiation times increased with visuospatial difficulty, whereas movement times remained within a similar range. The two groups differed in response initiation and movement execution times across all reaction time conditions. However, there was no disproportionate increase in response initiation times between an initial nonspatial condition and more complex visuospatial conditions in Parkinson disease patients, and the patients did not make more errors than control subjects. The results do not give support to the hypothesis of a generalised visuospatial deficit in Parkinson's disease.