The basic trial design is illustrated in Fig. 1A. Each trial began with the illumination of house lights that instructed the rat to nose-poke into the central port. Nose-poking initiated a 1,000-ms precue delay period. At the end of the precue delay period, a directional light located to the right or left of the rat was flashed for 100 ms. If the rat exited the port at any time prior to presentation of the directional cue, the trial was aborted and the house lights were extinguished. On 80% of trials, presentation of either the left or the right cue light signaled the direction of the fluid well in which the rat was to respond in order to obtain a liquid reward. On the remaining 20% of trials, the first cue was presented, but after a variable delay between 0 and 100 ms (selected with replacement from uniform distribution), the light opposite the location of the first cue was turned on and remained on until a behavioral response was made. These trials were referred to as STOP-change trials and were randomly
