Characterizing the Contributions of Discrete Hippocampal Subfields to Contextual and Cued Fear Conditioning Using Multiple Measures

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Accumulating evidence suggests that a number of psychological and emotional disorders, including phobias and post-traumatic stress syndrome, may in part reflect conditioned (learned) emotional responses to environmental stimuli. Among the many successful approaches used to explore the acquisition of conditioned emotional responses has been an examination of the acquisition, expression, and retention of Pavlovian fear conditioning in rats. In these studies, an initially neutral stimulus (the conditioned stimulus [CS], for example a tone, light, or odor) and an aversive unconditioned stimulus ([US], are typically paired in a forward manner. Following several pairings, subsequent re-exposure to the CS or to the context in which CS-US pairing took place elicits in rats a variety of behavioral and physiological responses, including increased heart rate and blood pressure, increased defecation and urination, and freezing behavior, collectively thought to reflect an internal state of "fear". An olfactory stimulus can serve effectively as a both a CS and a contextual stimulus in fear conditioning, and that the basic principles governing the acquisition of emotional responses conditioned to auditory and visual stimuli can be extended to the olfactory system. The proposed studies will examine the extent to which a particular brain structure, the hippocampus, participates in a variety of forms of Pavlovian fear conditioning. Based on both neuroanatomical and electrophysiological evidence, it is hypothesized that different sub-areas within the hippocampus will contribute to different "types" of emotional learning. Specifically, the hypotheses that dorsal hippocampus participates preferentially in learning about the emotional significance of places and that the ventral hippocampus is preferentially involved in learning about the emotional significance of internal states such as hunger or thirst, and that the entire hippocampus is involved in learning about the emotional significance of odors will be tested. Collectively these studies will significantly enhance our current understanding of the role of the hippocampus in emotional learning specifically and learning and memory processes in general. This project will involve undergraduate students and will recruit minority students from the Rutgers University Program "Research in Science and Engineering:".