Diurnal Arousal in Learning and Memory

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The brain’s ability to learn and remember is a topic of extensive debate and research. Mammals share many similarities, including the way in which information from the outside world is processed and stored. Mammalian circadian rhythms have long been thought to be essentially involved with these processes. This experiment is designed to explore the brain’s ability to process and store information at different times of the day. Changes in or the absence of circadian neurotransmitters lead to serious impairments correlated with sleep and wakefulness [1]. Orexin, one neurochemical that will be examined in this experiment, helps mediate arousal and has widespread projections throughout the brain, including the hippocampus [2]. In a study performed with rats in a four-quadrant water maze, it was found that orexin demonstrates a significant function in spatial learning and memory [3]. Norepinephrine, another neurotransmitter, is produced by brainstem nuclei and has been shown to help control wakefulness and sleep. Research also suggests that this system is important in responses to cognitive challenges, stress, and behavioral stimuli, due to one of its functions to enhance attention [4]. In this experiment, a water-filled radial maze is used to test the ability of mice to process spatial information at different times of the day. Specific structures of the brain involved in wakefulness and arousal are analyzed for differential neuronal activation during the course of the day and correlated with behavioral performance.

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