A neuronal model of memory - integrative processing in the retrosplenial head direction system

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Understanding memory is one of the most important scientific problems today, because of the devastating effects of memory loss (e.g., in Alzheimer?s disease). Remembering life events is closely linked to navigation, and so memory research has hitherto focused on spatial memory. Spatial memory is complex, however, and progress has been slow. The present proposal aims to develop a research programme studying a simpler version of spatial memory, memory for the landmarks that indicate directional heading and can be used to orient (such as one might orient using the statue of Eros, when emerging from the Piccadilly Underground). To remain oriented during movement, it is necessary to combine learned landmark information with information about self-motion. Both landmark learning and its combination with self-motion signals are thought to take place in a brain region known as retrosplenial cortex (RSC). Consistent with this idea, RSC becomes active when people learn about new environments, and damage to this structure (e.g., following stroke) causes both disorientation and amnesia. The present project will try to understand how landmark memory is formed in RSC, and how it is updated during self-motion. The activity of single RSC neurons will be observed while rats learn about new landmarks, or when familiar landmarks are moved, to try and determine what information the cells ?know? about the landmarks (colour, shape etc) and whether they also know about the spatial position of landmarks, or simply about their identity. Studies of groups of neurons will try to determine the extent to which they influence each other, as opposed to be influenced by the senses (such as vision). The goal is to try and determine whether the ?memory trace? for new landmark learning is located in RSC, and how this interacts with information about movement. If the project is successful, the RSC will be a valuable structure with which to pursue more complex questions about memory formation, such as what chemical signals are involved, and how these processes might be improved, for example with drugs. Thus, this work will not only help elucidate the processing pathways underpinning the sense of direction, but will also contribute more broadly to an understanding of the processes by which memories are formed and stored, and of how amnesia might be treated or even prevented.