Mice are trained with one session per day consisting of 250 trials. “High” and “low” probability ports are randomly assigned to the left and right port at the beginning of the session. All trials start with a 10-second illumination of the central port light. A central nosepoke within 10 seconds extinguishes the central nosepoke light and initiates the next phase of the trial. Trials in which the mouse fails to nosepoke during this window are recorded as center omissions. After the center nosepoke, cue lights on both side ports are illuminated for 10 seconds, and mice can nosepoke in either side port. Trials in which mice fail to nosepoke at a side port during this 10-second window are recorded as side omissions. A side nosepoke at the “high” probability port results in reward delivery (10uL) in the central port 80% of the time in both phase 5.1 and phase 5.2. A side nosepoke at the “low” probability port results in reward delivery in the central port 0% of the time in phase 5.1 or 20% of the time in phase 5.2. A side nosepoke at the “low” probability port results in reward delivery in the central port 0% of the time in phase 5.1 or 20% of the time in phase 5.2. Once a side port is selected, reward is delivered at the central port based on these probabilities and the central port light stays illuminated for 10 seconds. Once the central port light turns off, the intertrial interval (ITI) begins (a randomly selected period of time between 20-30 seconds). In Phase 5.1, a switch in the pairing of left and right ports with “high” (80%) and “low” (0%) probability of reward occurs periodically. Contingency reversals occur at a random frequency (every 7-23 rewarded trials) throughout the session.
Mice continue these sessions for a minimum of 6 days and maximum of 10 days; mice reaching a total of >80 rewarded trials over 3 cumulative days are classified as ‘learners’ and go to Phase5.2. If a mouse does not reach the >80 rewarded trials criterion after 10 days of training, it is labelled a ‘non-learner’, but still goes on to Phase5.2. In Phase5.2, trials have a similar structure, but the contingency switch only occurs when mice choose the high reward-probability port on >80% of the last 15 trials. All mice undergo 3 Phase5.2 sessions.