Figure 1.

Design of behavioral task. (A) Procedure of the light-side discrimination task. One of two pure tones (2 and 10 kHz) is constantly presented during the trial. The operant chamber is equipped with left (L), center (C), and right (R) sensor holes for nose-poke behavior. The bottom lines and arrows show the time course of events in one trial. (B) Sequence of blocks with different reward probability conditions. In each block of 25 trials, the reward probability is fixed to high (H, 80%) or low (L, 20%). The rats are informed of the high or low probability of the reward by one of the two pure tones. No tone is presented in inter-block intervals (IBI). (C) Sequence of blocks in the probe test. One of the two pure tones is presented in each block but rats obtain no reward. No tone is presented during the extinction phase.