Two previous posts have reviewed studies of the beneficial effects of exercise for depressed adults and adolescents. New research shows that aerobic exercise may even reverse memory loss in the aging brain.
The hippocampus, located in the brain’s temporal lobe, is associated with memory. It is instrumental in storing long-term memories. As we age, the hippocampus shrinks, which leads to memory loss. However, studies have investigated the possibility of reducing shrinking, and related memory loss, in the aging brain. One such area of research focuses on the effects of exercise on hippocampal shrinkage and memory loss.
In prior research, aerobic exercise has been found to positively impact brain anatomy and processes in older adults, including gray and white matter volume in the pre-frontal cortex, the executive control network of the brain, hippocampal and medial temporal lobe volumes, and cerebral blood volume (p. 3017).
The present study had two primary goals: to assess the role of aerobic exercise on hippocampal volume and on spatial memory. The researchers conducted a clinical trial (including a treatment group and a control group) to establish the potential changes in hippocampal volume and concomitant improvement in spatial memory as a result of exercise in elderly patients.
Participants selected for the study were older adults between the ages of 55 and 80 with no dementia or other potentially confounding disease states. These 120 participants were divided equally into treatment and control groups. The treatment group performed moderate-intensity aerobics three times per week for one year. The control group did only stretching and toning exercises for the same period of time.
Results were evaluated using magnetic resonance imaging (MRI) of the hippocampus conducted at three points in the study: baseline (prior to intervention), 6 months after baseline, and at completion of the intervention. The baseline MRI established that there were no significant differences between the two groups in hippocampal volume. During the intervention, participants did not differ significantly in attendance rates at training sessions, with each group attaining an almost 80% attendance rate. Fitness improvement was also assessed, with participants in the aerobic group developing a higher fitness level over the course of the study compared to the stretching group.
At the end of the 1-year intervention period, participants in the aerobic exercise group experienced a 2% increase in hippocampal volume in the left hemisphere and a 1.97% increase in the right hemisphere. The anterior region of the hippocampus was impacted, which controls spatial memory, but not the posterior region. In contrast, members of the stretching group experienced a decline in hippocampal volume (1.4% left and 1.43% right). “Our results demonstrate that the size of the hippocampus is modifiable in late adulthood and that moderate-intensity aerobic exercise is effective at reversing volume loss” (p. 3018).
Other physiological benefits were observed. The aerobic exercise group experienced a 7.78% improvement in maximal oxygen consumption, compared to only a 1.11% improvement in the stretching group.
What about existing fitness levels prior to beginning the study? Did those who were more fit experience less decline across the one-year period? This hypothesis was examined for the stretching group only: those with higher fitness levels prior to the study experienced less hippocampal volume loss across the one-year study compared to others in the same group.
The second goal of the study was to examine changes in spatial memory. The researchers hypothesized that spatial memory would improve as a result of aerobic exercise. Both groups showed improvement in spatial memory between baseline and the end of the study. However, baseline fitness level was associated with improved memory such that participants with a higher fitness level before the study experienced the most improvements in memory by the end of the experiment. When looking specifically at hippocampal volume at baseline and at the end of the experiment, it was associated with improved memory.
In summarizing the study’s outcomes, the authors noted: “aerobic exercise might elicit the greatest changes in regions that show the most precipitous decline in late adulthood, such as the anterior hippocampus and prefrontal cortex. Overall, these data suggest that the anterior hippocampus remains amenable to augmentation. These results clearly indicate that aerobic exercise is neuroprotective and that starting an exercise regimen later in life is not futile for either enhancing cognition or augmenting brain volume” (pp. 3020-3021).
Erickson, K. I., Voss, M. W., Prakash, R. S., Basak, C., Szabo, A., Chaddock, L., … & Kramer, A. F. (2011). Exercise training increases size of hippocampus and improves memory. Proceedings of the National Academy of Sciences, 108(7), 3017-3022.
©Jennie Dilworth, Ph.D