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For whom the bells toll: Networked circadian clocks in the brain

Erik Herzog
Department of Biology, Washington University , USA

Circadian regulation of brain activity is a well established phenomenon. Daily changes in spontaneous firing and responsivity have been: reported for many and diverse brain areas, traditionally associated with sleep and wake states and typically assumed to arise as a result of drive from the hypothalamic suprachiasmatic nuceus (SCN). With recent discoveries that cells outside the SCN have intrinsic circadian rhythms in gene expression, we have begun to investigate the potential for extra-SCN circadian pacemakers within the brain. We find a diversity of rhythmic capabilities depending upon brain area. One area, the main olfactory bulb ( OB ), has intrinsic daily rhythms in gene expression and firing rate which persist in vitro and in vivo in the absence of the SCN. This talk will focus on recent results implicating this circadian oscillator in local regulation of olfactory sensitivity and more global regulation of olfactory coding and locomotor behaviors.