response (termed reinforcement-inhibition or RFi cells; Figure 4C). Note that since inhibitions occurred at varying times relative to the response across individual cells, only 5 of the 9 type RFi cells are shown in the average PEH. For those locations, significant increases in [DA]s were observed (F8,152 = 4.0, p < 0.0001). Dopamine levels significantly increased 1 s prior to the response and remained significantly elevated 9 s after response completion. Finally, of the 75 NAc neurons, 46 cells (61%) showed no change in cell firing relative to the cocaine-reinforced response, termed nonphasic or NP cells. Remarkably, at only two locations at which NP cells were recorded did dopamine significantly change (both in the core) in response to the lever press, however no significant overall change in rapid dopamine release was observed when data was averaged (Figure 4D). The distribution of cell types across the core and shell and their relationship to phasic dopamine release are shown in Table 1.
