Fig. 2.

Identification of phasic response. In these plots, the average spike densities are aligned at the time of the cue onset. The schedule fraction is shown at the top. The phasic response was identified automatically by finding the peak average firing across all of the schedule fractions, shown here by asolid vertical line in the panelrepresenting the response in the 2/2 schedule. The beginning was defined as the minimum between 200 msec before the cue onset and the peak for this response, and the end of the responses was defined as the minimum between the peak and 1000 msec after the peak. These are shown by the dashed vertical lines in the panellabeled 2/2. This time period was then applied to the responses in all of the schedule fractions (dashed vertical lines). Theasterisk indicates that the peak response occurred for the indicated schedule, here 2/2. The same algorithm was used for bar release-related neurons and reward-related neurons, with the search periods being 200 msec before to 500 msec after bar release and 200 msec before to 750 msec after reward delivery, respectively.Ordinate: sp/s, spikes per second.