Exercise Activates Memory in Seniors

Fran Lowry

June 05, 2019

A single 30-minute session of moderate exercise on a stationary bicycle increases activation in the circuits of the brain that are associated with semantic memory retrieval — including the hippocampus — in healthy older adults, new research shows.

Carson Smith

"The hippocampus shrinks with age, and is the region of the brain that is attacked first in Alzheimer's disease," said investigator Carson Smith, MD, from the University of Maryland School of Public Health in College Park.

"We know that regular exercise can increase the volume of the hippocampus, but the current study gives new information that exercise has the ability to impact this important brain region," Smith reported at the American College of Sports Medicine 2019 Annual Meeting in Orlando.

For their study, Smith and his team measured brain activity after a single session of exercise in healthy older adults using functional MRI (fMRI). Results were also published in the Journal of the International Neuropsychological Society.

The 26 participants, 55 to 85 years of age, were asked to perform a memory task that involved identifying famous and nonfamous names.

"The action of remembering famous names activates a neural network related to semantic memory, which is known to deteriorate over time with memory loss," Smith explained.

Participants came into the lab on two different days. On day 1, they did 30 minutes on an exercise bicycle at moderate intensity, which was about 70% of their maximum capacity. On day 2, they just rested in a chair.

Thirty minutes after each exercise or rest, the participants underwent fMRI scanning. While in the scanner, they identified names as famous (e.g., Frank Sinatra) or not famous (random names selected from a phone book).

The memory test "was meant to be very easy because we wanted them to be successful remembering things," Smith said.

After exercise, activation was significantly greater in four cortical regions of the brain — the middle frontal gyrus, inferior temporal gyrus, middle temporal gyrus, and fusiform gyrus — than in the other regions.

Increased activation of the hippocampus was also seen on both sides of the brain after exercise.

This was not the result the investigators had been expecting.

In a previous study of older adults, Smith and another team of researchers showed that 12 weeks of moderate exercise decreased activation in the areas of the brain responsible for semantic memory, suggesting that exercise "enhanced neural efficiency" (J Alzheimers Dis. 2013;37:197-215).

To explain the discrepancy in these results, the investigators postulate that "the acute increase in neural activation after exercise may provide a stimulus for adaptation over repeated exercise sessions."

"I think this is somewhat analogous to exercising a muscle," Smith told Medscape Medical News. "When you exercise that muscle, you increase blood flow and the muscle becomes more efficient. Perhaps the brain is operating in the same manner, so that over time, as you exercise every day, your memory networks become more efficient."

The take-home message "is that a single session of exercise activates or prepares these neuronal networks to be activated. Being able to engage the memory network could be one of the reasons why exercise protects cognition," he added.

Teresa Liu-Ambrose

"This study adds evidence that exercise is beneficial for healthy cognitive aging," said Teresa Liu-Ambrose, PhD, PT, from the University of British Columbia in Vancouver, Canada.

But participants were healthy older adults. "Whether these effects will be seen in those with cognitive impairment still has to be assessed," she pointed out.

"Nevertheless, previous randomized controlled trials of chronic exercise training have demonstrated benefits for memory, as well as hippocampal volume, in older adults with and without cognitive impairment," Liu-Ambrose added.

The study was supported by the Department of Kinesiology at the University of Maryland. Smith and Liu-Ambrose have disclosed no relevant financial relationships.

American College of Sports Medicine (ACSM) 2019 Annual Meeting: Abstract 2026. Presented May 30, 2019.

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