I’ve been reading Spark by John J. Ratey, MD, who is a clinical associate professor of psychiatry at the Harvard Medical School. Based on a wealth of research, he describes the intimate link between exercise and the brain. In addition, he beautifully distills down and simplifies the complexities of brain function for everyone to comprehend, which is fundamental to understanding the connection. Just as working out can strengthen our cardiovascular system and muscles, so too can it strengthen and enhance brain function. The mind becomes more alert and can better focus. Tension is reduced. Moods improve and lead to an increase in motivation, drive and vitality. And since the brain is ultimately overseeing the function of every system within the body, its condition directly influences the body’s overall health.
A landmark study outlined in the beginning of the book demonstrated how exercise before school primed the brains of students in such a way that it enhanced the absorption, processing and remembering of information, resulting in better test scores, more confidence, higher levels of motivation and creativity, and in other words, greater success. But how does exercise do this? Fundamentally, it positively supports a property of the brain referred to as neuroplasticity. To say that the brain is plastic simply means that it is changeable. It is sculpted by the inputs it is given in an almost infinite number of combinations. Not surprising – the brain is composed of 100 billion neurons that inter-communicate to control our mind and body. And because our brains are always receiving new sensory inputs, they must continuously identify, sort through, interpret, catalog, cross-reference, retrieve and eliminate information. The ability to do this efficiently rests on the “physical” health and function of the neurons and their ability to interact with one another and regular physical activity helps to ensure that they do this at their optimum. There are three major ways that exercise supports brain health:
1. It increases the levels of neurotransmitters and balances neurochemicals in the brain
Nerve cells (or neurons) communicate with one another and eventually “bind” through a region of the cell called the synapse, a site where chemicals termed neurotransmitters (NTs) are released through structures called vesicles, to be take up by an adjacent cell. See figure below:
There are two major NTs, glutamate and gamma-aminobutyric acid (GABA). Glutamate is a stimulatory molecule, meaning that it promotes a connection between cells and a subsequent signaling network to develop. GABA is inhibitory, helping to balance the activity of glutamate. When the molecule glutamate is released from one cell’s synapse and accepted by a neighboring cell, it establishes the early signs of a connection that can initiate a signaling cascade involving the “firing” of many cells. Repeated firing between a set of cells will induce the formation of additional synapses that further strengthen the connection (see #3 below). This wiring process, which is set in motion by glutamate is a crucial step in learning.
A number of other NTs exist, but the following three, which are discussed frequently in the book are highly influential yet only produced in one percent of the brain’s neurons. They perform many functions but primarly act as regulators of information to ultimately balance brain neurochemicals:
Serotonin: Helps to control excessive brain activities that deal with mood that can lead to such things as aggression and impulsive behavior. Prosac is often prescribed to restore serotonin levels and to relieve depression, anxiety and obsessive-compulsive disorder.
Norepinephrine: also enhances mood and boosts signals related to attention, perception, motivation and arousal.
Dopamine: functions in learning, satisfaction, attention and movement. It is this NT that is elevated by Ritalin, the drug to treat attention-deficit hyperactivity disorder (ADHD).
It is pointed out that taking drugs to elevate the levels of a single NT may not necessarily restore the overall balance of neurochemicals in the brain. However, this is one of the things that exercise does naturally. For example, running elevates the levels of both serotonin and dopamine.
2. It encourages the development of new cells
A greater pool of cells to participate in learning. For a long time, it was believed that we were born with all the brain cells we would ever have, however, over ten years ago, it was discovered in the hippocampi (a region of the brain required for learning and memory) of terminally ill cancer patients that neurogenesis does occur after the brain has fully developed. This phenomenon has also been identified in chickadees that are learning new songs and interestingly, in mice that run on an exercise wheel, suggesting a link between exercise and neurogenesis. In addition, these newly formed cells can participate in learning.
New experiences promote the survival of new neurons. Although exercise helps to increase the pool of cells available for learning, it then comes down to our environment or the richness of our experiences that determines how many of them survive. In other words, without some sort of stimulation that activates the cells, i.e., without something new to learn, the cells have no reason to stick around. Indeed, many new cells do die from lack of use. And the numbers are the same in the brains of exercisers versus non-exercisers. The important thing is that there is a larger population of cells in brains that have “worked out”. And those brains are in a healthier position to want to learn.
Exercise can reverse degeneration. Studies focused on aging have also reported that the frontal cortex and temporal lobes in the elderly can increase in volume in response to exercise, presumably through the growth of new blood vessels as well as new neurons and connections. Better performance on test scores that target these regions have also observed in those that participate in aerobic activity. The prefrontal cortex is involved in high order brain functions, yet, ironically, it includes those things that we take for granted, like how to tie our shoes or drive to work. The temporal lobe is intimately connected with the hippocampus. It catalogs words and proper names and helps to maintain long-term memory. It is also a brain region that atrophies in Alzheimer’s Disease. As you can expect, it would be almost impossible to function on a day-to-day basis without these basic abilities. We would very quickly lose our independence. The good news is that physical activity can preserve our brain health, as well as our physical strength as we age, allowing us to care for ourselves for as long as possible.
3. Exercise encourages stronger connections between cells
Exercise increases levels of BDNF. Another class of chemicals acting in the brain is referred to neurotrophic factors. They help to assemble and maintain the infrastructure. One in particular, brain-derived neurotrophic factor (BDNF) has a number of functions within neurons, including strengthening the cells, protecting them from cell death, regulating the production of NTs such as serotonin and strengthening the connections between neurons through the sprouting of new branches, as discussed above. As a result, BDNF has been called “MiracleGro for the Brain”. This strengthening allows for something called long term potentiation (LTP), a process that increases the affinity between neuronal connections and allows learning to become sticky. This phenomenon occurs, for example, when you encounter something over and over again. If we learn something for the first time, an initial connection/circuit will be established, however, if we practice it repeatedly, the circuit becomes stronger through the formation of stronger and additional synapses. As expected, a lack of use will cause the connection to whither.
BDNF is required for laying down circuitry and its levels increase during learning as well as during physical activity. As mentioned above, the hippocampus is required for learning and is also susceptible to degeneration. In support of this, it’s been demonstrated in mice that the levels of BDNF increase in the hippocampus as a result of exercise. In addition, a study concluded that the rate of learning increases after exercise and this finding also correlated with levels of BDNF. Conversely, taking away BDNF was found to inhibit the learning process. This suggests that exercise is pivotal in keeping the learning process and a healthy brain alive.
Exercise alleviates the stress that can erode connections. We hear a lot about cortisol and how, through stress, it can ultimately lead to an increase in fat around the gut which is a high risk factor for cardiovascular disease. In the brain, cortisol is involved in the distribution of glucose, the primary source of energy. During an acutely stressful situation such as one that initiates the fight-or-flight response, the body is mobilized to take action, cortisol levels are driven up in the brain and glucose is conserved by diverting it from regions involved in thinking. In today’s world, that acute level of stress is frequent but rarely necessary and the body often does not follow through with sufficient movement that would dissipate the body’s biochemical reaction. This form of chronic disconnect that takes energy away from major parts of the brain such as the hippocampus, for example, eventually induces the degradation of its synapses and results in cell death. With regard to learning, the hippocampus is responsible for the who, what, when, where and how of our memories and works with another brain region called the amygdala that registers the emotional component. The hippocampus can be “taken over” by the amygdala if it breaks down and this imbalance contributes to the development of anxiety, fear, and depression.
Exercise also allows the resting tension in the body to drop, which also cuts off the stress signaling to the brain through the heart. An exercise-induced increase in heart rate triggers the production of atrial natiuretic peptide (ANP), which can dampen or block a stress response in the brain. It also leads to an increase in the production of GABA and serotonin, which can alleviate anxiety.
Exercise upregulates the production of growth factors. Exercise boosts the production of three growth factors (GFs) in the brain as well as throughout the body that are then transported to the brain via the blood stream and through the blood brain barrier:
1. IGF-1 works to help deliver fuel to the muscles. In addition, exercise promotes the production of insulin receptors on cells within the body that work with IGF-1 to promote the uptake of glucose and an increase in energy production. In the brain, IGF-1 plays a role in neurogenesis and LTP and it induces the synthesis of the NTs serotonin and glutamate.
2. VEGF (vascular endothelial growth factor) functions to increase oxygen delivery by helping to sprout additional capillaries in the body as well as in the brain.
3. FGF (fibroblast growth factor) promotes tissue growth in the body and is instrumental for LTP in the brain.
Exercise is a mild stress that strengthens neurons. The increase in GFs supplied through exercise strengthens neurons. Exercise is considered a mild stress for the brain because it generates molecular by-products such as free radicals that can damage cells. Through the help of increased GFs, neurons turn on genes that repair the damage, leaving the cells stronger. Additional, mild stresses include caloric restriction, learning and low levels of toxins such as those that naturally occur in food. One such toxin is sulfurophane, a compound made in cruciferous vegetables such as broccoli to ward off bugs. In the body, it induces our cells to turn on genes that produce their own arsenal of antioxidants. So although broccoli contains its own antioxidants, perhaps the greater benefit from eating it lies in its ability to exert our cells to ultimately make them stronger. Just as resistance training builds muscles by initially breaking them down, mild stresses such as exercise makes brain cells more resilient by working them more intensely as well.
So if you’d like to increase your vitality, improve and balance your mood, sharpen your learning capacity and memory and melt away stress, try pumping up your brain with exercise then give it something new and fascinating to do with all that power. It wants to be pushed and challenged regularly and will serve you well for far longer as long as it is.
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