Distinct roles for striatal subregions in mediating response processing revealed by focal excitotoxic lesions.

This study examined the relative roles of distinct striatal areas in response processing. Rats were trained on a reaction time task that enabled performance on each side of the rat's body to be assessed independently. Rats then received unilateral lesions of the whole dorsal striatum or restricted medial or lateral lesions. Both medial and lateral lesions induced a response bias in contralateral space, but this bias was less severe in rats with medial lesions. Medial striatal lesions led to an increase in premature responses. Lateral striatal lesions produced an increase in late responses. It is suggested that the lateral striatum mediates the selection of responses, and the medial striatum acts to influence inhibitory control over responding. Discrete striatal areas are thus functionally dissociable, but both have a crucial role in the organization of responding in space.