Fight, flight, focus: researchers find a pathway from exercise to cognition
The locus coeruleus norepinephrine system (LC-NE system), is the primary source of norepinephrine, the chemical behind the fight-or-flight response.
It’s a tried and true method for improving your focus: taking a break for a brisk walk.
But while research has shown that short bouts of exercise benefit your brain, it’s unclear exactly how.
New findings from Northeastern University suggests the system regulating the body’s fight-or-flight response might be an answer.
“For more than two decades, we’ve shown that there’s a beneficial relationship of a single dose of exercise on cognition,” said Charles Hillman, Michele and Anthony Manganaro distinguished professor and director of the Institute for Cognitive and Brain Health at Northeastern. “This is the first attempt to directly try and understand a mechanism that underpins that relationship in children.”
The research provides more evidence that children need opportunities for physical activities to optimize their physical and mental health. Understanding a mechanism by which exercise and the brain are connected also enables further exploration and understanding of how to maximize benefits to cognitive and brain health.
Scientists have long connected regular exercise with beneficial changes in brain function and structure including improved growth and survival of the neurons which receive, transmit and process information.
Hillman, who is in the departments of psychology and physical therapy, movement and rehabilitation sciences, and his lab has also found that short bouts of exercise – or ‘acute exercise’ – make you feel more focused and improves cognition. But you’re not really going to alter your brain structure after only 20 minutes, he said.
So, what’s giving your brain that added boost?
Hillman and colleagues Lauren Raine, an assistant professor in the institute and in the department of physical therapy, movement and rehabilitation sciences at Northeastern, and psychology postdoctoral researcher Christina Bertrand hypothesized that the locus coeruleus norepinephrine system, or LC-NE system, might play a role. Originating in the brain stem, the LC-NE system is the primary source of norepinephrine, a chemical behind the fight-or-flight response, for the central nervous system.
Previous research has suggested a link between acute exercise and changes in salivary alpha-amylase (sAA), an enzyme that, among other functions, indicates the brain is producing norepinephrine. SAA and the stress hormone cortisol have also been related to academic performance in children. Finally, the LC-NE system has been connected to attention, the basic cognitive function that enables people to focus.
“When you’re in a relaxed state you cast attention broadly,” Hillman explained. “But when something captures your attention and alerts you, you focus in – like in the case of fight or flight – and you determine whether or not it’s worth your time and attention.”
But no one had taken these separate “pieces” or “threads,” as Hillman called them, and connected them.
“We had all these pieces coming together, but not all the pieces tied together,” Hillman said.
So, to find out whether sAA could be the connection between acute exercise and improved brain function, researchers measured the brain activity and sAA of 104 children ages 9 and 10 before, during and after they completed a variety of interventions and a test. The interventions included an active stress test of a brisk 20-minute walk on a treadmill; a “psychosocial” stress test that included mathematics and public speaking; and the control condition was seated rest.
A cognitive test in the form of computer tests was to evaluate the subjects’ ability to suppress a response or actively ignore irrelevant distractions.
Brain activity was measured with an electric encephalogram cap, specialized headgear embedded with sensors that record electrical activity in the brain, before and after each of the interventions, while researchers collected sAA via “passive drool,” as Raine called it, seven times at each intervention.
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The researchers found that sAA increased slightly immediately after exercise then decreased below initial levels compared with when children were resting or completing the psychosocial stress test.
“It makes sense that something like exercise would rev up that fast flight-or-flight response system,” Bertrand said. “But what we see following exercise is a recalibrating of that stress system back to where the children started, or maybe even settled down even more.”
According to the research, post-exercise changes in sAA made children more consistent and slightly more accurate in their cognitive tests, indicating more consistent focus.
Cortisol, meanwhile, increased only in response to the psychosocial stressor – not exercise, according to the research. Higher levels of the stress hormone, however, made the children less reactive to changes in sAA and its cognitive benefits.
“If you come with lower cortisol, are less stressed, you’re showing greater modulation of brain function,” Hillman said. “But if your system is already stressed, stressing it more isn’t necessarily helpful.”
Hillman said the research did not involve adults, but he doesn’t see any reason why the LC-NE system would be significantly different in older individuals than in children.
Which gets to the ultimate question.
You have 20 minutes until a big test: do you take a walk or study?
“These data may suggest that going out and exercising beforehand would probably be helpful, assuming you had the information already learned,” Hillman said.
“But it would also then suggest…that if you weren’t prepared and you were already highly stressed, walking might not help you,” Raine, who is also in the department of medical sciences at Northeastern, continued.
And before you get your hopes up too high, Bertrand added a critical caveat.
“We could say it could help you attend to the task at hand and focus better,” Bertrand said. “We can’t promise a better test score.”
