|About the Book|
In the broadest sense, my interest in neuroscience has been in the understanding of mechanisms underlying the neural control of behavior. To more specifically address this broad topic, I have chosen to examine questions regarding the circadianMoreIn the broadest sense, my interest in neuroscience has been in the understanding of mechanisms underlying the neural control of behavior. To more specifically address this broad topic, I have chosen to examine questions regarding the circadian regulation of learning and memory as my thesis project. I believe that studying the crossroads of these two fields may be potentially beneficial to both. First, little is known about the direct output effects of the SCN and the circadian system. Studying circadian regulation of learning and memory may help to elucidate output mechanisms by which the SCN regulates physiological processes. Second, learning and memory is clearly dependent upon the state of the organism and the circadian system drives daily changes in the state of the organism that impacts a range of processes from gene expression to behavior. Furthermore, these daily changes in learned behavior can be used to identify molecules or genes involved in learning that also fluctuate between the day and the night, thereby linking the molecular genetics underlying learning and memory with the behavior. In studying the circadian regulation of learning and memory, I hope I have contributed positively to both fields of study.-The first chapter of my thesis details our investigation of the circadian regulation of hippocampal excitability and long term potentiation (LTP). The results provide the first evidence that an endogenous circadian oscillator modulates synaptic plasticity in the hippocampus. The second chapter of my thesis details our investigation of the impact of melatonin on hippocampal long term potentiation and excitability. The results suggest that hippocampal synaptic plasticity may be constrained by melatonin through a mechanism involving MT2 receptor mediated regulation of the adenylyl cyclase/protein kinase A pathway. Genes responsible for generating circadian oscillations are expressed in a variety of brain regions not typically associated with circadian timing. The functions of this clock gene expression are largely unknown, and in the third and final chapter of my thesis, we sought to explore the role of a key circadian gene, Period2 (mPer2) in hippocampal physiology and learned behavior. Together, the results provide evidence that the clock gene mPer2 plays a critical role in synaptic plasticity and in the recall of some forms of learned behavior.