Unilateral Stimulation of the Dorsolateral Striatum Attenuates Goal-Directed Action.

It has long been known that the dorsomedial (DMS) and dorsolateral striatum (DLS) mediate distinct forms of action control, with DMS mediating goal-directed actions and DLS mediating habits. Recent evidence suggests that, in accord with its role in goal-directed control, unilateral stimulation of dorsomedial striatum (DMS) enhances actions contralateral to the stimulation in a manner that scales with the prior reward history of that action. In the current study, we assessed whether the effects of unilateral stimulation of the dorsolateral striatum (DLS) induce a response bias that reflects enhanced habitual control, as measured by the effect of stimulation on ongoing goal-directed control. Rats were first trained to press two levers for distinct outcomes in a manner likely to induce goal-directed control of these actions. We then assessed the effects of unilateral hM3D DREADDs-induced stimulation of the DMS or DLS, applied during an outcome devaluation choice test and outcome-mediated reinstatement, both known to depend on DMS activity. DMS stimulation had no impact on the choice of either the action ipsilateral or contralateral to the stimulation, either during devaluation or reinstatement. In contrast, stimulation of the DLS abolished goal-directed control in both tests, reducing sensitivity to outcome devaluation both on the ipsilateral and contralateral lever. In addition, stimulation both attenuated reinstatement and induced a response bias away from the contralateral lever during reinstated responding. These data suggest that, rather than driving motor output per se, the DLS is important for selecting motor programs triggered by stimulus-response associations.