Neural systems underlying episodic memory: insights from animal research

Two strategies used to uncover neural systems for episodic-like memory in a nimals are discussed (i) an attribute of episodic memory (what? when? where ?) is examined in order to reveal the neuronal interactions supporting that component of memory; and (ii) the connections of a structure thought to be central to episodic memory in humans are studied at a level of detail not feasible in humans. By focusing on spatial memory (where?) and the hippocam pus, it has proved possible to bring the strategies together. A review of l esion, disconnection and immediate early-gene studies in animals reveals th e importance of interactions between the hippocampus and specific nuclei in the diencephalon (most notably the anterior thalamic nuclei) for spatial m emory. Other parts, of this extended hippocampal system include the mammill ary bodies and the posterior cingulate (retrosplenial) cortex. Furthermore, by combining lesion and immediate early-gene studies it is possible to sho w how the loss of one component structure or tract can influence the remain ing regions in this group of structures. The validity of this convergent ap proach is supported by new findings showing that the same set of regions is implicated in anterograde amnesia in humans.