MIZUMORI, Sheri J.Y.: A neural systems analysis of adaptive navigation in rodents

The hippocampus is thought to be critical for adaptive navigation since hippocampal lesions produce deficits in visual spatial learning, and hippocampal neurons fire relative to an animal’s location in space. Hippocampal ‘place cells’ are thought to contribute to a place code that is derived from knowledge about the spatial relationships between components of the visual environment. However, behavioral studies show that rats can rapidly and effectively switch from spatial to nonspatial strategies while solving tasks if visual cues become unreliable. Thus, animals process multiple forms of sensory information in parallel, linking them in a context-specific way. We suggest that this process involves more than just the hippocampus; the retrosplenial cortex (RC) and the striatum may contribute to the flexible use of cognitive strategies during navigation. Anatomical and physiological evidence indicate that the RC may play a special role in the integration of visual and self-generated information about one’s own movements and orientation in space. Furthermore RC may associate visual and nonvisual (i.e. self motion) cues to update memory representations elsewhere, as well as engage the retrieval of appropriate associations during the performance of familiar spatial tasks. Single unit data will be presented that lend initial support for these interpretations of RC function. The striatum, on the other hand, may evaluate the reinforcement consequences of specific behaviors exhibited in particular environmental contexts. Consistent with this view, striatal unit data will also be presented. It will be argued that cooperative interactions between hippocampus, neocortex and striatum allow animals to readily adopt the most efficient strategy during navigation. (Supported by MH58755)