2012年2月8日水曜日

Ventral Striatum Encodes Past and Predicted Value Independent of Motor Contingencies


Brandon L. Goldstein, Brian R. Barnett, Gloria Vasquez, Steven C. Tobia, Vadim Kashtelyan, Amanda C. Burton, Daniel W. Bryden, and Matthew R. Roesch
J. Neurosci. 2012;32 2027-2036
http://www.jneurosci.org/cgi/content/abstract/32/6/2027?etoc

The ventral striatum (VS) is thought to signal the predicted value of expected outcomes. However, it is still unclear whether VS can encode value independently from variables often yoked to value such as response direction and latency. Expectations of high value reward are often associated with a particular action and faster latencies. To address this issue we trained rats to perform a task in which the size of the predicted reward was signaled before the instrumental response was instructed. Instrumental directional cues were presented briefly at a variable onset to reduce accuracy and increase reaction time. Rats were more accurate and slower when a large versus small reward was at stake. We found that activity in VS was high during odors that predicted large reward even though reaction times were slower under these conditions. In addition to these effects, we found that activity before the reward predicting cue reflected past and predicted reward. These results demonstrate that VS can encode value independent of motor contingencies and that the role of VS in goal-directed behavior is not just to increase vigor of specific actions when more is at stake.

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