How does exercise improve brain function?

An article by Eric Nagourney in an issue of The New York Times, “Exercise: Working Out the Memory as Well as the Muscles,” describes a study conducted at the Columbia University Medical Center, which was led by neurologist, Dr. Scott A. Small. The study shows how exercise may stimulate growth of neurons in a part of the brain associated with memory loss. Researchers looked at changes in the brains of volunteers who worked out on exercise equipment to compare the findings with earlier research involving mice. Using an MRI and treadmills, the scientists were able to see whether blood flow increased to the same part of the brain in humans as it had in mice. It did, suggesting working out may help produce neurons in a part of the brain that loses them disproportionately as people age. The researchers also found as the volunteers went through a three-month exercise period, their scores on memory tests went up. “Our study does suggest that it’s probably aerobic exercise that’s inducing this effect,” Dr. Small said.

An issue of Newsweek includes several articles entitled "Health for Life: Exercise and the Brain.” The lead article by Mary Carmichael is titled “Stronger, Faster, Smarter.” She reports the exercising process begins in the muscles, where contractions release a chemical messenger protein called IGF-1 that travels through the bloodstream and into the brain. “There, IGF-1 takes on the role of foreman in the body’s neurotransmitter factory. It issues orders to ramp up production of several chemicals, including one called brain-derived neurotrophic factor,
or BDNF.” It refuels the mind/brain.

Harvard psychiatrist, John J. Ratey, M.D., is the author of Spark: The Revolutionary New Science of Exercise and the Brain. He calls the BDNF molecule “Miracle-Gro for the brain.” It fuels most of the activities that lead to higher thought. With regular exercise, the body builds up levels of BDNF, which results in the branching out of brain neurons and the creation of new interconnections among them. Consequently, neurons communicate with one another in new ways. This process underlies ongoing learning: changes in the synapses between neurons are involved in storing new facts and making them available for future use. BDNF makes the process possible and brains with more of it have a greater capacity for knowledge. You see exercise underlies neuroplasticity and improves mind/brain function.

Hard data from MRI’s reveal that individuals who suffer from Alzheimer’s show a significant amount of brain atrophy in the areas of the hippocampus, parietal region, and temporal cortex.  The mechanism by which exercise can slow brain atrophy during normal aging is that it helps to maintain the size of the hippocampus. As is widely known, individuals with Alzheimer’s have a reduced hippocampus. This means that individuals who exercise less will have more brain atrophy when compared to individuals who exercise more.

Exercise has been shown to slow brain atrophy as it may help aid in the growth of neurons in the brain. This is evidenced by studies that indicate that an increase of blood flow in the brain helps retain its size. The decrease of the brain is associated with Alzheimer’s disease.  Furthermore, exercising causes muscles to contract, which causes IGF-1’s to be released into the bloodstream and, essentially, into the brain. Once IGF-1 reaches the brain, it then becomes a neurotransmitter and helps stimulate the production of brain-derived neurotrophic factor (BDNF).

Through exercise the body builds BDNF, which helps with activities that stimulate mental activity by causing the neurons to branch out and create connections between them. In turn, changes that occur in these synapses between the neuro-pathways are beneficial, as it allows the brain to be stimulated, thus reducing atrophy, along with creating a greater capacity for the retention of information. Essentially, exercise aids in the process of neuroplasticity and helps improve the overall mental mechanisms.   

Additionally, the level or intensity of exercise has been linked to the reduction of the expression of Apo-e4 gene, which aids in decreasing the beta-amyloid plaque found throughout the body. Furthermore, exercise has been also linked to increase the length of telomeres. The lengthening of telomeres has additionally been linked with slowing down the aging process.  Lastly, exercising regularly can help increase the amount of blood that reaches the brain and allows for a rich nourishment of oxygen and nutrients to these cells. By helping nourish these hormones and cells in the brain, exercise reduces the amino-acids that damage the part of the brain that deal with memory, as it prevents the brain from decreasing in size.

There are several ways exercise can improve the brain. First  exercise will increase blood flow to the brain, providing the brain with essential nutrients such as glucose and oxygen.
Abnormal glucose tolerance can lead to brain impairments, and exercise helps regulate blood sugar levels.
In children, exercise has been shown to improve cognitive function, and improve motor skill development. Children who are active do better on standardized tests and have better grades. In adults, especially as we age, regular physical activity increases memory and slows the aging process of the brain. Studies show that very active people who engage regularly physical activities have much lower rates of memory loss, dementia, Alzheimer’s and do better on cognitive function tests over time.

New research shows that staying committed to exercise over the long haul gives you the brain structure of someone years younger.

When researchers performed brain imaging tests on adults between the ages of 60 and 80, the noggins of the most active people looked similar to the brains of people years younger. The exercisers' small blood vessels looked less twisty, suggesting better cerebral blood flow -- which translates to healthier mind muscle and better brain function.

In the study, the heavy exercisers didn't just go through the motions. They had gotten at least 3 hours of exercise a week for 10 years. It's not clear yet whether the long-term exercise caused favorable changes in the study subjects' brain anatomy or if the people with healthier brains were simply more likely to exercise.

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