A major goal of behavioral neuroscience research is the identification of the neurobiological processes which underlie learning and memory. One important model system for examining experience-based changes in neuronal activity is long-term potentiation, or LTP. This is a relatively long-lasting change in the efficiency of synapses, which results from stimulation with a brief, high frequency train of weak electrical pulses. This form of "neuronal plasticity" was first discovered in the hippocampal formation, a brain region known to be involved in memory formation. Dr. Rose' recent work has shown that by using a pattern of electrical stimulation which mimics either of two prominent electrophysiological activity patterns of the hippocampus (complex spike discharge and theta rhythm), he could markedly reduce the threshold for inducing LTP. This effect, termed "primed burst" (PB) potentiation, is invoked quite reliably by as few as five appropriately patterned stimuli. Because of its low threshold, and of its similarity to well-known electrical activity patterns, it is proposed that a PB-like process may occur within the hippocampus during the formation of new memories. Dr. Rose is recording electrophysiological activity from the hippocampi of normal, awake rats to evaluate this hypothesis. This work is clarifying both the physiological and behavioral conditions which promote PB potentiation, thus suggesting their role in the learning process. He is also examining the correlation between PB potentiation and memory by examining the effects of stress and aging (two conditions known to impair mnemonic function) upon the capacity of hippocampal synapses to show this PB effect.
