April 20, 2021
Aerobic exercise may help to rewire our brains, improving connections in areas critical for memory as we age, according to a new report. The findings could help to explain why regular exercise has been linked to a lower risk of Alzheimer’s disease.
The findings come from a study of 34 older African-Americans who participated in a dance program from researchers at Rutgers University-Newark’s Aging & Brain Health Alliance in New Jersey. All were over 60 and generally healthy, though none were regular exercisers at the start of the study.
Over the next 20 weeks, some took part in a twice weekly, hour-long aerobic dance class that was conducted at various churches and community centers in Newark. The classes were of moderate intensity and designed to raise the heart rate. The others went about their normal routines.
MRI brain scans revealed that those who participated in the aerobic exercise classes had increased brain activity and communication in a part of the brain called the medial temporal lobe. That part of the brain contains the hippocampus, a brain area critical for learning-and-memory and one of the first brain regions affected by Alzheimer’s disease.
The scientists suggest that the regular aerobic workouts allowed networks of neurons in the medial temporal lobe to be reinforced in healthier new ways, sharpening memory function. In contrast, older men and women who remained sedentary had more rigid brain connections, in which different parts of the memory circuits appeared to get “stuck.”
The study’s senior author, Mark A. Gluck, a professor of neuroscience and public health at Rutgers who has been studying Alzheimer’s disease for decades, compared the situation going on in the brain to being at two different kinds of dinner parties: a lively party, and a dull one.
“At the lively party, guests jump around regularly from conversation to conversation, breaking off repeatedly into different groups to talk about various topics,” he said. “In contrast, at the dull party, you get stuck talking all night long to the same small set of people. Exercise has a similar effect on your brain. It allows the memory circuits to be more flexible, jumping from conversation to conversation with different parts of the brain.”
The fact that exercise appeared to improve brain connections and neural flexibility in the medial temporal lobe, the seat of the hippocampus, may have implications for warding off Alzheimer’s disease.
“This is the same brain region where damage from Alzheimer’s disease appears, often years before the onset of noticeable dementia,” said Neha Sinha, the study’s lead author. “As such, these studies add to our understanding of how regular aerobic exercise may protect us from Alzheimer’s dementia.”
Older men and women who participated in the exercise program also showed improvements in cognitive skills. On thinking skills tests designed to measure the ability to retain information and apply it to new situations, those who exercised were better able to apply old memories to new situations and tasks. They improved their ability to generalize learning from the past and more efficiently transfer old knowledge to new challenges.
Earlier research from the group showed that older people who carried a gene variant known as ABCA7 may have fewer cognitive benefits from exercise than those who don’t carry the variant. Carrying the ABCA7 gene raises the risk that someone will develop Alzheimer’s disease.
Scientists have long known that modifiable behaviors such as diet, exercise and physical fitness may reduce the risk, or delay the onset, of Alzheimer’s disease and other forms of dementia. Earlier studies have also shown that in older people, regular exercise helps slow the loss of brain volume and bulk up new brain cell creation in the hippocampus, which may help to prevent age-related memory loss and lower the risk of dementia.
But while participants in the current study showed cognitive and brain improvements with regular aerobic exercise, researchers do not know if physical activity is slowing any underlying damage done by Alzheimer’s disease.
It is possible, Dr. Gluck noted, that the benefits of exercise are only compensatory, allowing people with Alzheimer’s disease to function at a higher level without changing their underlying brain damage. The group is planning additional studies using newly developed blood tests that measure markers of Alzheimer’s to better assess whether regular exercise might help to slow disease progression.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Neha Sinha, Chelsie N. Berg, Michael A. Yassa, Mark A. Gluck: “Increased dynamic flexibility in the medial temporal lobe network following an exercise intervention mediates generalization of prior learning.” Neurobiology of Learning and Memory, Vol. 177, January 2021