It has been postulated that the NAc is comprised of ‘neuronal ensembles’ or groups of cells with similar functional properties that are activated by synchronous excitation of their inputs (Pennartz et al., 1994). Within this framework, dopamine functions as a neuromodulator, gating the activation of NAc neurons by glutamatergic inputs from the BLA, hippocampus and PFC, and influences NAc output (Mogenson et al., 1980; Pennartz et al., 1994; Nicola et al., 2000; Carelli & Wightman, 2004). Our findings that dopamine release in the NAc occurs primarily at locations at which patterned activation of NAc neurons are recorded, even in the presence of cocaine, supports this view. The correlation of dopamine release and cell firing across both the core and shell indicates that dopamine is equally positioned within both sub-regions to influence the activation of specific sets of NAc neurons.
