As we leave summer behind and plunge into fall, you can expect to notice the sun rising later and setting earlier.
These seasonal light changes have long been known to impact everything from eating patterns and sleep to hormonal and brain activity.
But, according to a new study conducted by researchers at the University of California San Diego School of Medicine, the colder months’ shorter days can also spur behavioral changes.
This finding was discovered after researchers used a mouse model to analyze a unique process in which neurons change the expression of neurotransmitters in response to the length of daylight. And these changes in expression ultimately led to disrupted behavior.
Much of the work focused on a region located within the hypothalamus– which is the part of the brain that produces hormones controlling hunger, mood, body temperature, heart rate, and more.
And within the hypothalamus is a small structure known as the suprachiasmatic nucleus (SCN). The SCN is responsible for keeping time, if you will, and regulating humans’ circadian rhythm– in other words, the mental, physical, and behavioral changes that follow a twenty-four-hour cycle and impact nearly every bodily function.
And interestingly, the SCN operates using input from photosensitive cells located in the retina– which are able to communicate even the slightest changes in day length and light to the rest of our bodies.
So, the study described how about twenty thousand SCN neurons essentially coordinate with each other to keep up with and adapt to differing day lengths.
And in mice, the researchers specifically found that the neurons alter their expression of critical neurotransmitters, which ultimately results in changed brain activity and daily behaviors.
morrowlight – stock.adobe.com – illustrative purpose only, not the actual person
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Moreover, seasonal light changes were also found to alter numerous neurons in the paraventricular nucleus (PVN)– another region of the brain that is critical in controlling stress, growth, metabolism, reproduction, and immunity.
“The most impressive new finding in this study is that we discovered how to artificially manipulate the activity of specific SCN neurons and successfully induce dopamine expression within the hypothalamic PVN network,” Dulcis explained.
In other words, the researchers believe their study is groundbreaking because it provides a novel explanation of how the brain reacts to seasonal light changes. Plus, equipped with these findings, scientists now have an actionable target to offer new treatments for disorders associated with seasonal light exposure changes.
To read the study’s complete findings, which have since been published in Science Advances, visit the link here.
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