How Different Seasons Affect The Way Your Brain Works

You've probably experienced fluctuating moods with the seasons, but there's a good chance you never realized that your brain activity also differs based on seasonal changes -- varying between spring, summer, fall and winter -- as a new study has shown.

The Belgian study, published this week in the journal Proceedings of the National Academy of Sciences, finds that the brain utilizes its resources differently to perform the same cognitive tasks depending on what season it is. 

"Seasonal fluctuations are important in animals," Dr. Gilles Vandewalle, a neuroscientist at the University of Liege and the study's lead author, told The Huffington Post in an email. "Mood and immunity are well known to change with seasons in humans and there are indications that several brain aspects could also be seasonal."

For the study, the researchers measured brain function in 28 Belgian adults during all four seasons of the year. At each session, the participants spent four- and-a-half days in a lab, without access to the outside world or to sunlight -- so they were completely sheltered from seasonal cues. After that time period, the participants' brains were scanned while they completed a task requiring sustained attention, and another task requiring them to exercise their working memory. 

Their test scores did not change at different times of the year, however the neural "cost" of that performance differed. In the summer, brain activity peaked on the attention tasks. During the winter, they used significantly less brain activity involved in attention. On the memory task, brain activity peaked in autumn and hit a low in the spring. 

So, the brain is more active in the summer when attention tasks are being performed, where as in the fall memory recall uses more brain activity.

What does this suggest? It's possible that the brain adapts its level of efficiency to the time of year. 

"A bigger activation can mean that there is more means available to do the task such that it is easier," Vandewalle said. "Lower activation in winter can mean that the brain is less efficient and that it will be more difficult to do the task and in a way more costly because requiring more other resources to maintain performance." 

The researchers don't yet know why these seasonal brain changes occur, and they're not the first to study seasonal biological processes. they're not the only biological processes that seem to vary with the seasons. 

Scientists have shown that mood can change with the seasons, as well as metabolism (it's easier to gain weight in the winter). The activity of human genes also changes with the seasons, and so can immune system activity. A study last year also found that we may perceive colors differently in summer compared with winter.

But this new study is the first to show that brain activity related to attention and memory may also have a seasonal element. Anna Wirz-Justice, a chronobiologist at the University of Basel who was not involved in the study, expressed excitement over the findings. 

"Even though we live in an artificial environment with light cycles that are no longer seasonal, we have the programming in our brains to respond to seasonality,” she told Scientific American.

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