The dorsomedial striatum mediates flexible choice behavior in spatial tasks

The dorsomedial striatum plays a critical role in action selection and evaluation as well as in value-based decision making. Rodent studies implicated the posterior subregion of the dorsomedial striatum (pDMS) in acquisition and expression of action-outcome associations and in choosing actions that lead to rewarded locations. However, it is not clear whether the pDMS is involved in action selection based on an assessment of the efforts and outcomes of the available response options. Here we investigated in rats the effects of pDMS cell body lesions on effort-based decision making in a cost-benefit T-maze task. In this task, subjects could either choose to climb a barrier to obtain a high reward in one arm or a low reward in the other arm without a barrier. Furthermore, the effects of pDMS cell body lesions were examined in this task after a spatial alteration of reward allocation to analyze flexibility of choice behavior. Results revealed that choice behavior based on an assessment of cost-benefit ratios of the available response options was intact in rats with pDMS lesions. However, relative to sham controls, choice behavior in rats with pDMS lesions was less flexible after a spatial reversal of the high and low reward goal arm. Thus, in a T-maze task as used here, the pDMS may not support effort-related decision making, but flexibility of spatially guided behavior. (C) 2011 Elsevier B.V. All rights reserved.