The nucleus accumbens: an interface between cognition, emotion, and action.

Nearly 40 years of research on the function of the nucleus accumbens (NAc) has provided a wealth of information on its contributions to behavior but has also yielded controversies and misconceptions regarding these functions. A primary tenet of this review is that, rather than serving as a "reward" center, the NAc plays a key role in action selection, integrating cognitive and affective information processed by frontal and temporal lobe regions to augment the efficiency and vigor of appetitively or aversively motivated behaviors. Its involvement in these functions is most prominent when the appropriate course of action is ambiguous, uncertain, laden with distractors, or in a state of flux. To this end, different subregions of the NAc play dissociable roles in refining action selection, promoting approach toward motivationally relevant stimuli, suppressing inappropriate actions so that goals may be obtained more efficiently, and encoding action outcomes that guide the direction of subsequent ones.