Mechanisms of spatial memory

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The hippocampus is a crucial brain structure for spatial cognition (among other things), in reptiles, birds and mammals. However, after many decades of research, its precise role is still the subject of considerable controversy. Our lab has been investigating the role of the hippocampus in spatial memory and navigation using a variety of techniques, including computational (neural network) modelling and human memory experiments in virtual reality (VR) environments. We are beginning to understand the conditions under which people rely on cognitive maps, and the cues they draw upon to form those maps. The proposed research will further our understanding of these processes. Our computational models of the hippocampal memory system will be extended to take into account the fact that people use multiple strategies for navigation. While some people tend to favor a cognitive map strategy, others favor a landmark strategy, based more on motor memory than spatial memory (e.g. "turn left at the supermarket"). Our models will help to shed light on the neural mechanisms that may subserve these complex functions. Complementing this theoretical work, experimental methods will be used to test predictions of the model and shed further light on the conditions governing the use of cognitive maps. Our past research indicates that objects at navigationally relevant locations such as major intersections in a virtual town tend to be remembered better than other objects on tests of spatial memory, even though other objects are remembered equally well on tests of recognition memory. If objects are encoded as part of a cognitive map, rather than simply being remembered as part of "visual snapshots" or motor memories, people should be able to reliably locate these objects when tested from a range of unfamiliar viewpoints. Moreover, they should be able to remember the locations of objects after long delays, as opposed to relying upon spatial working memory and mental imagery. In the long term, our work could have important implications not only for understanding the basic mechanisms underlying spatial cognition, but for rehabilitating individuals with spatial memory and navigation deficits, as are common with ageing.