Behavioural and neuroanatomical evidence in episodic memory in the rat

Abstract

In an attempt to test the hypothesis that rat's can perform very similar behaviours to episodic memory in humans, we here develop a novel Paviovian conditioning procedure demonstrating integrated what- where-when representations. Rats explored two distinctive contexts, one in the morning and the other in the evening. Subsequently, either in the morning or the evening, they received a foot shock immediately upon entry into a third context that equally resembled the two explored contexts. When conditioned freezing was measured at an intermediate time of day, rats showed significantly more fear of the context congruent with the time of day of the foot shock. Thus, rats automatically form an integrated time-place memory that can be flexibly updated by future events, essential characteristics of episodic memory. Furthermore, it is shown that these memories rely upon some of the same neuroanatomical structures, including the medial prefrontal cortex and the hippocampus, as are specifically required for episodic memory in humans.