“Photoperiod and Brain Blood Flow: Changing Day Length to Alter Cerebral Perfusion”

“Two bits of information, the absolute day length, and whether day lengths are increasing or decreasing, signal time of year and whether winter is approaching or receding. This information is coded in the body by the hormonal melatonin signal, which is suppressed by light and secreted exclusively at night. Using the information from duration of melatonin secretion animals can measure day length (an ability called photoperiodism) and respond to the shortening days of fall by reorganizing their physiology and behavior…
short days are associated with reduced learning and memory, hippocampal neurogenesis, and impaired long-term potentiation (LTP) along the Shaffer-collateral-CA1 pathway. What could be causing these deficits in cognitive capacity in response to short days? We hypothesized that changes in learning and memory would be preceded by a reduction in blood flow to the hippocampus, a primary brain structure that controls spatial memory formation…
Our study demonstrated that in addition to these factors, day length can contribute to seasonal plasticity in blood flow. These findings may have implications for seasonal changes in cognitive functions in humans, as recent studies report that short photoperiods are associated with reduced hippocampal volumes in a large community sample. Short-day reductions in blood flow may have additional implications for seasonal changes in cardiovascular disease, as the incidence of stroke is increased during the short days of winter.”


Very cool study, exciting future directions. It makes me want to add photoperiod adjustments to my future work.

I have so many questions about how this is regulated… it also seems like it would be easy to mine existing human fMRI data to confirm that this is true for us.

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