Our Brains on Summer

It’s summer. Sure the official start date was June 21 but since I was a kid, summer starts on the last day of school. In my household we have finally hit that benchmark.

My summers were filled with camp, hanging out at the waterpark, and spending days reading about Maggie Adams and Queen Elizabeth’s court. Now, summer is spent trying to figure ways that I can look at anything besides a computer screen. And I love the longer days because my early morning workouts are now done in daylight. Basically, I really enjoy summer.

But not everyone does. Just like it’s polar opposite winter, summer can wield its influence on our brains. One way is that there are a small percentage of people who suffer from SAD, or Seasonal Affective Disorder, during this time of year. The long sunny days make them feel blue. And unfortunately for these depressives, much isn’t known about how to treat this long-light version of SAD since most research has examined its colder cousin that occurs during winter. However, science may be finding its way toward an explanation. Biologists at Vanderbilt University may have figured out the mechanism in which the seasons affect our brain.

Reporting in a May 2015 issue of the journal Current Biology, they identify the area of the brain that is affected by the seasonal light cycles that drive SAD. It’s a small region in the mid-brain called the dorsal raphe nucleus. Never heard of it? Join the club. Apparently it houses many of the specialized neurons that control our levels of serotonin—the hormone that determines our mood. When serotonin is abundant, we are happy and when our brains are a serotonin wasteland, we’re depressed or sad.

Shifting beach-y, sun-soaked daydreams into deep, dark thoughts aren’t the only things that our brain may do during summer, its telling time. Turns out that our brain may not need a calendar to know what season it is, suggests a Japanese study published in the recent issue of the Proceedings of the National Academy of Sciences. It turns out that there is an area of our brain that keeps seasonal time—think of it as a large-scale version of the circadian rhythms that dictate our sleep-wake cycle. Both are controlled by the suprachiasmatic nucleus aka SCN in the brain. The SCN expresses (or broadcasts since SCN sounds like a television network) certain genes during the 24 hours that make up our day. Two SCN regions synchronize their gene expression during the short days of winter but then fall out of phase as the days get longer as in summer. Think of it watching the same program on television but in two different rooms of your house: there is always a bit of lag between the two broadcasts. Now imagine if you left the TV on all day and that lag time increased; that is what happens in the SCN regions during summer.

I am sure there are many other things that summer does to our brain, like overheat it. But there is one thing that we should make sure we do for our brain: give it a real vacation.

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