Different representation of forthcoming reward in nucleus accumbens and medial prefrontal cortex.

We recorded single units in the rat nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC) to investigate activity related to reward mediation and anticipation during execution of an alternating reward task. NAcc and mPFC neurons showed increased activity differently during an interposed delay preceding reward delivery. Some NAcc neurons increased their activity specifically during the delay period before reward presentation, discriminating forthcoming food or water presentation. A subset of neurons in the mPFC similarly discriminated between food and water reward during the delay; however, about half did not discriminate reward qualities. These results show that the NAcc and the mPFC contribute differently to the organization and execution of goal-directed behavior.