Sexual dimorphic circuits in photoperiodic encoding and photic processing

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PROJECT SUMMARY/ABSTRACT Light regulates neurological function through circuits that remain poorly defined, and there remains a significant unmet need in understanding photic plasticity in the brain of both sexes. For example, seasonal changes in day length (i.e., photoperiod) modulate sleep, attention, appetite, metabolism, mood, and immune function occur in a large number of people, with up to 80% being women. The suprachiasmatic nucleus (SCN) drives circadian and photoperiodic responses to light, but there is a large gap in our understanding of sex differences in SCN photic and photoperiodic processing. Our preliminary data indicate that circadian and photoperiodic responses differ by sex, with females display larger behavioral responses to light mediated by divergent SCN circuits. Based on these data, we propose the central hypothesis that photic processing differs between males and females because the retina-SCN circuit is sexual dimorphic. We will test that biological sex influences cellular responses to light (Aim1), photoperiodic responses to day length (Aim2), and neural adaptations in SCN circuits (Aim3). These studies will benefit from the collective expertise of this collaborative research team, which specializes in retinal physiology, SCN network properties, cellular imaging, and computational analyses. Independent of sex differences, successful completion of these studies will provide novel insights into neural mechanisms of photic processing and photoperiodic encoding to advance understanding in both sexes. Further, this work is expected to provide information that will be critical to better understanding diseases incurred by other forms of light-induced disruption (e.g., shiftwork, jetlag).