Scientists have known for a long time that exercise improves brain health. However, how and why exercise improved mental fitness was much of a mystery. Until now that is.
A team of researchers led by Richard Maddock, a professor in the Department of Psychiatry and Behavioral Sciences, have established a link between intense exercise and increased levels of two common neurotransmitters called glutamate and GABA (gamma-aminobutyric acid).
In the brain, the cells communicate using neurotransmitters. Scientists have identified deficiency in certain neurotransmitters to be an underlying cause of specific neuropsychiatric disorders.
For example, a common signature of major depressive disorder is depleted levels of glutamate and GABA (the exact same neurotransmitters Maddock’s team recorded high levels of following intense exercise). Interestingly, when normal health is restored, the previously depleted glutamate and GABA levels return to normal levels.
According to Maddock, exercise triggers the metabolic pathway that replenishes these neurotransmitters. This finding thus promotes the likelihood of using exercise to treat neuropsychiatric disorders linked with deficiencies in neurotransmitters such as major depressive disorder.
Going further, the study also helped resolve another mystery concerning how the brain uses the fuel it consumes during exercise. Typically, the brain consumes a lot of fuel, in fact more than any other organ in the body. During exercise, it consumes even more.
What it uses this extra energy for has always been anyone’s guess. Thanks to the research, it appears the brain uses part of the fuel to make more neurotransmitters. This explanation may only account for a small percentage of the energy consumption of the brain during exercise. However, it represents an important step towards understanding the complex inner workings of the brain.
Aside providing two long-sought answers, the study does tell more about how much a sedentary lifestyle can negatively affect brain health as well as the potential role of the brain in athletic endurance.
The researchers undertook the experiment using a group of 38 healthy volunteers. The volunteers exercised on a stationary bicycle until their heart rate hit approximately 85% of their predicted maximum heart rate.
The team kept track of glutamate and GABA levels using a powerful 3-tesla (3T) MRI. The team measured the levels in two different parts of the brain immediately before carrying out the exercise and immediately after completing three vigorous exercise sessions. The team then crossed the data collected from the participants who exercised with the data collected from a control group that did not exercise.
The comparison showed increased levels of glutamate and GABA in those who exercised, and no change among those who did not exercise. Furthermore, the team noted significant increases in the visual cortex and anterior cingulate cortex.
The visual cortex is responsible for processing visual information. The anterior cingulate cortex helps regulate heart rate, emotion and some cognitive function.
An important observation was that while the increased levels eventually subsided over time, the team identified evidence of longer-lasting effects. To put it clearly, it was possible to tell how much one had exercised in one week by reading the resting levels of glutamate in the following week.
This is encouraging as it further lends credence to the possibility that exercise could form the basis for an alternative therapy for depression. If this materializes, it would actually be the preferred option for patients under the age of 25, who sometimes experience more side effects from medications taken to adjust neurotransmitter levels.
In the near future, Maddock and his team hope to figure out if a less-intense exercise, like walking, offers similar brain benefits. Furthermore, they would like to use their method to study patients with depression to find out what types of exercise offered the most benefit.
The team published their findings in The Journal of Neuroscience.