Doctoral Dissertation Research: Hippocampal Modulation of Auditory Representations

With National Science Foundation support, Mr. Orduna and his advisor Dr. Gluck will conduct a year long investigation of how auditory discrimination training affects cortical representations of complex sounds. The natural environment is full of complex sounds containing a variety of information relevant to behavior. Learning about sounds or images can lead to changes in perceptual sensitivities that facilitate the processing of behaviorally relevant events. Although the neural mechanisms underlying these changes are not well understood, they are thought to depend on the brain's capacity to adaptively modify its cortical representations of sensations. Orduna and Gluck will measure electrophysiological responses of rats and humans to complex sounds before and after subjects have been trained to discriminate these sounds. Computational models of cortical and hippocampal processing suggest that the hippocampus modifies cortical representations to facilitate learning. The investigators will evaluate the role of the hippocampus in auditory learning by comparing learning-induced representational changes (measured as changes in evoked responses) in the auditory cortices of normal and hippocampal-lesioned rats. The joint use of behavioral and electrophysiological techniques, in combination with lesion techniques, will facilitate comparisons between the neural mechanisms underlying auditory learning in humans and other mammals. This project will illustrate a new way of evaluating current theories of how the cortex and the hippocampus interact during learning and memory processes. These scientific results should provide new knowledge about the brain basis of learning and memory.