Why Am I (and All Of Us) So Tired Around 2pm

If the massive energy supplement market is any indication, a lot of people tend to feel a little groggy towards the middle of the day, say around 1 or 2 pm. Well, researchers from the Swinburne University of Technology have looked into this little issue to learn more about the midday lethargy.

Published in the Journal of Neuroscience the study indicates something quite interesting. The study suggests that this afternoon dip in energy has something to do with our reward-processing center in the brain. Apparently, activity in this region fo the brain peaks in the morning and in the evening; and what goes up must come down. Apparently that come down is typically around 2pm.

In the study, the research team compared activity in the brain region, at least for young men, during a gambling task at the hours of 10am, 2pm, and 7pm. They found that activation in the brain’s left putamen—that’s the part related to reward response—hit its lowest point in the middle of the afternoon.

Study author Greg Murray, of the Swinburne University of Technology explains, “Understanding how the activity in the brain’s reward system changes throughout the day could have implications for depression, substance abuse, and sleep disturbances.”

Making this summary Jamie Byrne, Ph.D. candidate and lead study author reports, “Our best bet is that the brain is ‘expecting’ rewards at some times of day more than others, because it is adaptively primed by the body clock.” He also divulges a bit on the brain’s interpretation of both intrinsic (personal value or integrity) and extrinsic (money or prizes) rewards.

A primary conclusion links the brain’s reward expectations with the natural circadian rhythms; this is totally in tune with how the wakefulness hormones work. Basically, the brain does not expect a reward in the morning or the evening, simply because of how the hormones are fluctuating at those times of the day (waking up is, apparently, reward enough). However, in the middle of the day, this part of the brain wants rewards.

Byrnes likens the brain response to different expectations on your birthday. When you expect a party—you plan one, for example—is something you expect, so the reward expectation is very high. In fact, you might even have to work a little harder to enjoy it. On the other hand, if you were not expecting a surprise party, you might just simply enjoy it.

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