Neurobiological Analyses of Plasticity: Learning and Memory

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The long-term goal of Dr. Thompson's research is to understand how the mammalian brain codes, stores, and retrieves memories. This has proved to be one of the most complex problems in the fields of neuroscience and psychology. It is also one of the most important. Over the course of evolution, biological organisms have developed two ways of storing information. One is the familiar genetic code embedded in the DNA; the other, no less important, is the ability to store acquired information and experience in the brain. In order to understand the mechanisms of memory storage, it is necessary to identify the specific circuitry in the brain required to store a given type of memory. Dr. Thompson has selected a basic form of associative learning shared equally by humans and other mammals, classical conditioning of discrete behavioral responses learned to deal with aversive events. An example of such conditioning is learning to close the eyelid in response to a tone (conditional stimulus, or CS) that signals the occurrence of a puff of air on the eye (unconditional stimulus, or US). Dr. Thompson and his colleagues have discovered that very discrete regions of the cerebellum are essential for this basic form of learning. They have also succeeded in identifying most of the essential brain circuitry involved in this basic form of associative learning. Dr. Thompson and his colleagues will use several neurophysiological methods and behavioral training procedures to (1) complete the identification of the essential auditory CS pathway, (2) determine whether or not memory traces are formed in this pathway before it reaches the cerebellum, (3) characterize the patterns of neuronal response in the essential US pathway and in the essential conditional- response pathway, (4) determine the exact locations where memory traces are formed, (5) begin analysis of the mechanism of memory-trace formation, (6) determine if the essential cerebellar circuit can mediate the "cognitive" behavioral phenomenon of "blocking," and (7) explore how higher brain structures (cerebral cortex, hippocampus) modulate the essential cerebellar memory-trace circuit. In addition to understanding basic mechanisms of memory storage, Dr. Thompson's work offers the promise of understanding how motor skills are coded and learned. The potential practical applications range from treatment of learning disabilities to enhancement of skilled human performance to the development of an entirely new approach to the problem of control of movement in robotics.