That mid-afternoon slump that seems so familiar isn't really about having too much food at lunch, or not having enough sugar. While a candy bar commercial might make you think you need a sweet treat to be yourself again, the reality is it's likely the brain's reward center that's responsible for the afternoon fog and not a lack of chocolatey goodness.
The region of the brain that processes reward feelings is the least active during this mid-afternoon period, regardless of food intake and that is what leads to the lack of motivation and a feeling of fatigue that can be overwhelming.The way our brains process reward is thought to be intricately connected with mood disorders and even addiction. A disruption in this region could be part of the biology behind depression and other mood disorders. The research, from a team at the Swinburne University of Technology in Australia suggests that when the brain slows down in processing rewards, the result is a lack of vigor, a feeling of tiredness and a dip in productivity. Understanding how the brain's reward system can ebb and flow could lead to new and better treatments for substance abuse, depression, and anxiety.
Experts have gone back and forth over what causes a slump in attention and productivity after lunch. From blood sugar to chemicals in food, the information has been confusing at times. The team at Swinburne used a gambling task, something the brain responds to because winning a game is an easily recognizable reward in the brain. Using 16 healthy young men, the activity was carried out at intervals during the day. Times included 10 am, 2 pm and 7 pm.
While the volunteers were engaged in the task, functional MRI scans (fMRI) were conducted to show, in real time, which areas of the brain were active. Looking at the blood oxygen levels on these scans was how the activity was determined, and the results were a bit of a surprise. It's been thought that the reward center was least active at night and more active during the day, following the circadian rhythm of work and sleep, however, it's a bit of a paradox. The brain has learned to expect rewards during the more active daylight times, so it doesn't work as hard to get them. It's as if "rest leads to rust" as it does in physical exercise.
When completing the tasks, the MRIs of the volunteers showed much less activity during the day. This lack of activity is what leads to that blah feeling of low productivity. The activity takes place in a region of the brain called the left putamen. Since it's been ingrained in most of us that rewards come during the day, without much activity required to seek them out, this region takes a bit of a break, and that slowed down effect is felt. Since we tend to not expect rewards first thing in the morning or the evening, the brain goes into a busy phase of actively searching for reward opportunities, and that provides more of a boost.
Jamie Byrne, a clinical psychology Ph.D. candidate at Australia's Swinburne University of Technology, and lead author of the new study explained, "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 circadian system." In other words, it's not about the food; the brain is just wired this way so step away from that candy bar. Going forward the team would like to see how the information can be used to plan a more productive day or ward off depression symptoms, but first, a larger study would need to happen, and then more data can be analyzed. The video below has more information, check it out.