a second increase in dopamine (maximum of 157 nM) approximately 4 s following the lever press response. The [DA] increase relative to the lever press was confirmed with principal component regression (Figure 3 bottom, blue trace superimposed on the peri-event histogram, PEH). Also illustrated in the bottom portion of Figure 3 is a PEH and corresponding raster display that show the activity of a single NAc neuron simultaneously recorded. In this case, the neuron showed an increase in cell firing that began within 1 s following response completion, and maintained a sustained increase in firing (maximum of 11.7 Hz) during the 10 s post-response period.
