Lauren Dempsey, MS in Biomedicine and Law, RN, FISM News
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New research from the University of California San Diego School of Medicine shows how changes in the length of the day directly impact the brain.
Davide Dulcis, senior study author and associate professor in the Department of Psychiatry at UC San Diego School of Medicine and member of the Center for Circadian Biology at UC San Diego, led the team of researchers. Dulcis’s team used mice to evaluate how neurons are affected by changes in day length and the subsequent behavioral changes that occurred in response to variations in light exposure.
The study was published earlier this month in Science Advances and details how seasonal changes directly correlate with sleep, appetite, hormones, and brain activity. This is because neurons in the suprachiasmatic nucleus (SCN) communicate these changes from the retina to the rest of the body. The SCN is the part of the brain that regulates each person’s own biological clock, or circadian rhythms.
Researchers found in the mice model that seasonal changes are being recorded at a cellular level. They were able to “artificially manipulate the activity of specific SCN neurons and successfully induce dopamine expression within the hypothalamic PVN network,” Dulcis told UC San Diego News Center.
Dulcis and his team explain how the SCN neurons work together to adapt to changes in daylight and found that “the SCN explicitly encodes seasonal changes in photoperiod by the relative phases of daily rhythms of electrical activity and clock gene expression of individual SCN neurons” as well as “alter the number of neurotransmitters expressing neurons in the paraventricular nucleus (PVN).”
These changes occur in the part of the brain that controls stress, metabolism, growth, reproduction, the immune system, and other functions.
Alessandra Porcu, Ph.D. is a researcher in Dulcis’s lab and the first author of the study.
“We revealed novel molecular adaptations of the SCN-PVN network in response to day length in adjusting hypothalamic function and daily behavior,” Porcu said. “The multi-synaptic neurotransmitter switching we showed in this study might provide the anatomical/functional link mediating the seasonal changes in mood and the effects of light therapy.”
The authors are hopeful that the findings of their research will help to explain how the brain adapts and is impacted by daily light exposure from seasonal changes as well as how to better treat disorders that are a result of those associated with these changes.
The National Institute of Mental Health (NIMH) estimates that millions of Americans suffer from a type of depression called seasonal affective disorder (SAD), especially in Northern areas where daylight hours are shorter in the winter. It usually occurs in winter and lasts about 4-5 months. Women are four times more likely to be diagnosed than men. Treatment for SAD usually includes light therapy, psychotherapy, vitamin D, and antidepressant medications that can be used in combination with one another.