Figure 2.

Representative patterns of responding for an individual rat across 3 consecutive sessions of saline, histamine, spiradoline, or remifentanil paired with one lever (Lever A; i.e., before a lever reversal). Percent choice for the infusion + a pellet (left panels) and corresponding heat maps depicting response type for each trial (right panels). Trial-by-trial performance is color-coded as follows: white represents no response (an omission); light gray represents a response for a pellet only; and dark gray represents a response for the infusion + a pellet. The preceding condition to saline was no infusion (i.e., before surgery). The preceding condition to histamine (1.0 mg/kg/infusion) was saline (paired with Lever A, reversal). The preceding condition to both spiradoline (0.056 mg/kg/infusion) and remifentanil (0.01 mg/kg/infusion) was histamine (paired with Lever A, reversal).