Automatic activation of motor programs by object affordances in patients with Parkinson's disease.

Clinical observations of kinesia paradoxica and freezing in patients with Parkinson's disease suggest that the automatic activation of motor programmes by visual stimuli may not require intact basal ganglia function, and that an increased sensitivity to such object affordances may contribute to some symptoms of the disease. Employing a paradigm that measures the degree of interference from object affordances on voluntary actions, we confirm that activation of object affordances are preserved in Parkinson's disease, but find no evidence that there is an increased sensitivity to the effects of object affordances on voluntary action.