Semantic activation in patients with Parkinson's disease.

Fifteen patients with Parkinson's Disease and fifteen age matched control subjects performed a reaction time task which permitted the separation of gross motoric slowing from the slowing of an internal mental process. The Parkinsonian subjects were slower overall than controls, indicating the expected slowing in their gross motoric responses. However, there was no difference between the Parkinsonian subjects and the control subjects in the speed of internal mental processing. These results suggest that PD may not impair an automatic process like access to semantic memory.