Apicella_1989_Brain.Behav.Evol_33_171

Unilateral injections of 6-hydroxydopamine into the substantia nigra of monkeys disrupted the initiation of learned movements performed with the contralateral forelimb. Failure to respond was observed in two types of behavioral tasks. The one involved a hand movement directed towards a target and the other, hand withdrawal without any spatial requirements at the end of the movement. The results suggest that the ability to perform the required response was recovered more quickly in the case of the task involving visually controlled movement.