The striatum and self-paced movements

Monkeys (Macacca fascicularis) were tested for their ability to perform learned, self-initiated arm movements for reward, both before and after receiving bilateral putamen lesions. The rate at which they made the movements was significantly reduced postoperatively, but their performance on a visually cued control task was normal. It is argued that the impairment was not a consequence of poor motor control or motivation, but that it reflected a reduced capacity to recall learned movements in the absence of external cues. The results complement similar findings for monkeys with supplementary motor cortex (SMA) lesions; the putamen is interconnected with the SMA in a cortico-striatal-thalamocortical loop.