Performance on delayed response tasks by patients with parkinsonism.

Eleven post-thalamotomy Parkinson's disease patients, and 11 post-operative, age matched, spinal control subjects, were tested on three visual discrimination matching tasks, two of which involved a delay in response. Error and reaction time scores were recorded. The former produced no differentiation but reaction time scores were significantly faster for the control group on the two tasks involving delay in response but not for the `no-delay' task. Since the motor components of all three tasks were the same, this significant difference in reaction time scores was attributed to the factor of delay in response, and treated as evidence that basal ganglia damage in humans can produce a purely cognitive impairment. The role of sensorimotor interactions, as another factor in this deficit, was also discussed.