Figure 1. IA task.

(a) Schema of the light-dark box used for the IA task. Rats were housed in a home cage. On the training day, a brief electrical foot shock (2 s) was applied in the dark box in the shock cage. (b) Thirty minutes after IA training, the trained rats consistently showed a longer latency before entering the dark side of the box (**F _{1, 14}=26.841, P<0.001 versus before, n=8, one-way factorial ANOVA, error bars indicate ±s.e.m.).