Fig. 1

a Task schematic, showing sequence of events in one trial (left panels) 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 an additional fluid bolus (i.e., large reward), whereas the opposite well offered 1 bolus (i.e., small reward). The reward stipulations again reversed in Block 4. b Percent choice on free-choice trials in each value manipulation over the first ten and last ten trials of each block averaged across animals and sessions (controls, black bars; cocaine, gray bars). c Percent correct on forced-choice trials in the same manner as b. d Reaction time (odor port exit minus odor offset) on all free-choice trials for each value manipulation. e Reaction time (odor port exit minus odor offset) on forced-choice trials in the same manner as b and c. For these analyses, behavior was looked at by session. f Average number of lever presses during sucrose (black) or cocaine (gray) self-administration averaged across rats for each day (days 1–12). g, h Location of recording sites (Paxinos and Watson). Gray boxes mark the extent of the recording locations. Sucrose control group n = 6; cocaine group n = 4. Error bars indicate SEM. Asterisks (*) indicate significance (p < 0.05) in multi-factor ANOVA and/or post-hoc t-tests