The use of metric and non metric cues in memory: an investigation using reversal learning in appetitive and non-appetitive tasks

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The ability to navigate in our environment and remember the location of objects in that environment is central to survival. Changes in location have long been correlated with changes in cell activity in the hippocampus, a brain region known to be important for spatial learning and navigation. Evidence suggests that this hippocampal cell activity is controlled by the distance and angle/direction properties of an environment (metric) and other properties such as wall color and lighting (non-metric). These are the same types of cues that allow us, behaviourally, to distinguish between two environments. My recent work, using a response reversal paradigm (a rat is trained to turn right on a T-maze and then subsequently trained to turn left, thus the rat learns competing responses that produce interference between memories), has shown that metric properties, particularly direction, are the most important feature in distinguishing between two locations and allowing an animal to make a location-specific response. The research described in the present proposal will use a rat model to continue to investigate the role of direction in a variety of learning tasks and also to assess the role of another metric property, distance. These results should allow us to understand how we use spatial information to prevent interference between memories that are formed. A better understanding of basic memory processes and factors that interfere with memory retrieval, allows us to determine what processes are compromised when memory fails. In order to treat or slow the progression of memory failure due to such disorders as Alzheimer's disease and dementia (disorders which affect the hippocampus), we first need to know how cells within the hippocampus are influenced by environmental cues and how this manifests itself in behavioral change.