Fig. 1.

Schematic diagram of the experimental design. (A) Fear conditioning phase, two CSs (e.g., red light and blue light) were paired with a shock (CS+E, CS+NE) at a partial reinforcement rate of 60%. A third CS (e.g., a yellow light) was never paired with a shock (CS−). This phase consisted of 32 trials: 8 CS+E, 8 CS+NE, and 16 CS−. (B) Extinction learning phase, the CS+E was presented in absence of a shock along with the CS− for 32 trials: 16 CS+E and 16 CS. The CS+NE was not presented in this phase. On Day 2, the (C) Extinction Recall phase 32 trials: 8 CS+E, 8 CS+NE, and 16 CS− were presented in the absence of a shock. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)