Figure 2.

A graphical representation of the behavioral windows used for analysis. The firing rates on each trial were segmented as depicted, splitting the trial into behaviors directed into the VI nosepoke and FI nosepoke. Periods of time in which the rat held its snout within the nosepoke aperture were analyzed, as were brief intervals just following or preceding these nosepoking windows. Responding on the VI nosepoke prior to responding on the FI nosepoke were classified as the VI1 period, and responding on the VI nosepoke following FI responding were classified as the VI2 period. The first 200 ms following the onset of each poke was deemed a poke initiation and is designated in green. The final 200 ms preceding the offset of each poke was deemed a poke termination and is designated in red. The time between poke initiation and poke termination was deemed a nosepoke hold and is colored grey for VI nosepoke holds and light blue for FI nosepoke holds. In order to switch from the VI nosepoke to the FI nosepoke, and vice-versa, the rat had to retreat down a hallway around current VI nosepoke and enter another hallway to advance toward the FI nosepoke. We classified the first and last 200 ms intervals of these switch periods as transitions. The retreat portion is designated yellow, and the procession portion is designated in dark blue. Some, but not all, response periods had multiple pokes/holds (e.g., VI1 here). Therefore, a mean firing rate for each response phase was computed. The response holds lasted varying durations, and the firing rate was simply reported as the total spike count/total duration of the hold. The remaining analytic windows (Poke Initiation, Poke Termination, Transition Retreat, and Transition advance) were of a fixed length, and were further split into ten 20 ms bins to evaluate changes in spike pattern (not shown). To identify whether a single neuron was modulated by the variables in question, repeated measure ANOVAs were conducted by comparing windows of equivalent color, representing equivalent behaviors, with each segment composing a within-subject phase. Individual trials served as “subjects.” Trials were randomly chosen to have the active VI nosepoke on the left or right side of the operant chamber, and the spatial position of the active nosepoke served as a between-subjects factor.