EMMA ULMER, PT, DPT, ATC
Emma can be reached at firstname.lastname@example.org.
What happens to the brain in winter?
It is that time of year again when the “holiday excitement” of winter is over, the days are still shorter, and we have hit multiple days of sub-zero temperatures with the great North Dakota wind howling.
A lot of people I have talked to lately report the “winter blues” are setting in. I am here to tell you that you are not alone. Many changes happen during the winter inside all of our brains that you may not know. Serotonin levels can be a culprit to the winter blues, but also the size of your brain may have an affect on your movement.
Serotonin is a chemical in your brain that is involved in eating/feeding behaviors, emotions, sleeping, and energy levels. The metabolism of serotonin fluctuates with seasonal changes and responds to light variations. This is how it is linked to winter. With less light in winter, serotonin gets quickly inactivated and has less time to work in our brain as compared to spring/summer months. Even though we can’t change how serotonin responds during winter months, there are ways we can increase effects of serotonin in our brain.
Sunshine: Increasing our exposure to light can help with serotonin levels. Sitting by a window or using light therapy to help boost serotonin levels.
Exercise: Exercise has been shown to have anti-depressant effects in the brain which parallels the effects of serotonin.
Not only does the metabolism of serotonin in the brain change, the actual size of the brain changes!
Throughout the year, there are two changes in brain size that are affected by seasonal change. First, the subcortical structures increase in size during winter while the cerebellum decreases in size. As the seasons change back into spring/summer, the opposite occurs. This raises the question of why this happens and how can we best use our natural brain changes to our advantage.
Subcortical – responsible for complex functions like learning, motivation, decision-making, and emotional and sensory processing
Cerebellum – responsible for the fluidity of complex movements, coordination; ex. Like hitting a baseball
The underlying cause of brain size change is still very unclear.
However, there are two theories out there that have been proposed to explain this.
Theory 1: Blood flow through the brain fluctuates with atmospheric pressure which is typically lower in the summer and higher in the winter. Oxygen levels are also affected by pressure changes requiring the brain to adjust blood flow into the brain. Thus, if we have more blood flow into the brain, theoretically, the brain should increase in size. Then why does the cerebellum decrease in size? The cerebellum shares blood supply with the brain stem but has a different blood supply than the rest of the brain.
Theory 2: The change in brain size is a vestigial reflex (a response that has lost its apparent function). When looking at research, the cerebellum shows the largest changes in size throughout the seasonal changes and is evolutionarily the oldest part of the human brain. To better explain this theory, let’s take a look at a smaller mammal. In the winter months, a shrew shrinks both in brain and body size. As the weather becomes warmer, the shrew returns to normal size. It is believed that a shrew shrinks in the fall to save energy throughout the winter. So, perhaps the human brain at one point in history changed with the seasons as a survival tactic, sacrificing some brain function to do so.
Even though we may lose some of our ability to complete complex movements due to our cerebellum decreasing in size, we have a better ability to use our subcortical functions like learning, motivation, and decision-making. So, use these cold winter months to accomplish your never-ending to do lists and learn a new skill.
Before you know it, the days with be filled with warm weather, your serotonin levels will naturally rise, and our brain size will change again.
EMMA ULMER, PT, DPT, ATC