The hippocampal formation is part of the brain known to be critically involved in learning and memory. Hippocampal damage in humans caused profound, nearly global amnesia for events which occur after the lesion. One type of ability affected is spatial, or navigational learning. Individuals with hippocampal damage cannot learn their way around a new environment. Some insight into how the hippocampus may accomplish its role in spatial learning has come from studies which examine the activity of single cells in the hippocampus in vertebrates as they navigate in an environment. In each part of the hippocampal region studied to date, cells show striking spatial correlates. Cells in one region fire in a location-specific manner, so that they are active only when the animal is within a particular, circumscribed region of space. Cells in another area fire only when the animal is facing a particular direction, regardless of its location. In yet a third area, cells fire as a function of both direction and location. Dr. Sharp will examine the spatial firing correlates of the cells in the hippocampal area. She will examine the basic spatial firing properties of cells in part of the hippocampal region which have not yet been studies. This will provide novel information about the nature of the spatial signal in the hippocampal formation. In addition, Dr. Sharp will conduct analytical studies to discover the sensory and mnemonic determinants of the spatial firing properties of cells in these areas, as well as in areas in which the basic spatial properties are already known. Another aspect of her work will be to examine changes in hippocampal physiology which result from exposing animals to spatially-complex environments. These long-lasting changes are thought to possibly reflect information storage mechanisms in the hippocampus. Thus, examination of the timecourse, mechanisms, and conditions of such neuronal plasticity could provide insight into how the hippocampal area orchestrates learning. Dr. Sharp's results will be used to try to understand the role played by the hippocampus in learning and memory, specifically as it relates to the onset of Alzheimer's disease in the aging brain.***//
