Figure 1. A, Task schematic showing sequence of events in one trial (left) and the sequence of blocks in a session (right). Rats were required to nose poke in the odor port for 0.5 s before the odor turned on for 0.5 s instructing them to respond to the adjacent fluid wells below where they would receive liquid sucrose reward after 500–7000 ms. For each recording session, one fluid well was arbitrarily designated as short (a short 500 ms delay before reward) and the other designated as long (a relatively long 1–7 s delay before reward) (Block 1). After the first block of trials (∼60 trials), contingencies unexpectedly reversed (Block 2). With the transition to Block 3, the delays to reward were held constant across wells (500 ms), but the size of the reward was manipulated. The well designated as long during the previous block now offered two to three fluid boli, whereas the opposite well offered one bolus. The reward stipulations again reversed in Block 4. B, Percentage choice on free-choice trials in each value manipulation over the first 10 and last 10 trials of each block averaged across animals and sessions (controls, black bars; cocaine, gray bars). C, Percentage correct on forced-choice trials in the same manner as B. For these analyses, the sample was behavior associated with each unit to better represent changes in behavioral output as it relates to the firing rates of single neurons that contribute to the single-unit and population analysis described below. D, Reaction time (odor port exit minus odor offset) on forced-choice trials in the same manner as B and C. E, Reaction time (odor port exit minus odor offset) on all free-choice trials for each value manipulation. F, Response bias for each session and each rat in each group computed for free- and forced-choice trials by subtracting the percentage of low-value choice from high-value choice (divided by the sum) for each session and subtracting the percentage correct on low-value trials from the percentage correct on high-value trials (divided by the sum) for each session and then averaging over the two. Each color represents a single rat; small dots represent each session and large dots represent the median overall all sessions within one rat. *p < 0.05, #p = 0.06, t test. Error bars indicate SEM. G, H, Location of recording sites (Paxinos and Watson). Gray boxes mark the extent of the recording locations.