Exercise Increases Hippocampal Volume and Improves Memory

 

The hippocampus is the area in the brain primarily associated with the formation of memories. It is believed that the hippocampus is principally involved in storing long-term memories and in making those memories resistant to forgetting.¹ Several researchers from the fields of psychology and kinesiology came together to evaluate whether there is a relationship between the hippocampus and physical activity in older individuals.²

 

The study assessed the effect of moderate-intensity physical activity on hippocampal volume changes in older adults (ages 55-80) over the course of 1 year. Aerobic exercise resulted in a 2% increase in hippocampal volume after a year, effectively reversing the typical age-related volume loss of that time period. The researchers concluded that the results of their study demonstrated that aerobic exercise training was effective at reversing hippocampal volume loss in late adulthood, which was accompanied by improved memory function.

 

The basis of this study was that previous research has demonstrated that the hippocampus shrinks in late adulthood, leading to impaired memory and increased risk for dementia. The researchers noted that previous research also demonstrated that adults with higher fitness levels have larger hippocampal and medial temporal lobe volumes, and that physical activity training increases hippocampal perfusion. However, the effects of aerobic exercise training on hippocampal volume in late adulthood remains unknown.

The researchers recruited 842 community-dwelling older adults, of which 179 enrolled in their study. Eligible participants had to demonstrate strong right handedness, be between the ages of 55 and 80, score >51 on the modified Mini-Mental Status Examination, score <3 on the Geriatric Depression scale (to rule out depression), have normal vision, have a corrected visual acuity of at least 20/40, have no history of neurological diseases or infarcts (Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, or stroke), have no history of major vasculature problems, including cardiovascular disease or diabetes, report being currently sedentary (physical activity for 30 minutes or less in the last 6 months), obtain consent from their physician, and sign an informed consent form approved by the University of Illinois.

After eligibility was determined, participants received an initial blood draw, magnetic resonance imaging (MRI) session, computerized spatial memory test, and fitness assessment and then were randomized into a moderate-intensity aerobic exercise group (aerobic walking) (n=60) or stretching and toning control group (n=60). They completed the MRI, fitness assessment, and memory tests again after 6-months. They also performed a repeat in the MRI, memory test, fitness assessment, and blood testing upon completion of the study, after 1 year.

The participants in the aerobic exercise group were supervised by a trained fitness leader for all sessions. They started by walking for 10 minutes and increased walking duration weekly by 5-minute increments until their duration reached 40-minutes (week 7), and then they maintained that 40-minute duration for the remainder of the program. Each walking session began and ended with 5 minutes of stretching for the purpose of warming-up and cooling-down. All aerobic exercise participants wore heart rate monitors and were encouraged to walk in their target heart rate zone of 50%-60% for weeks 1 to 7 and 60%-75% for the remainder of the program.

The participants in the stretching and toning control group were also led by trained exercise leaders. Their program included a similar warm-up and cool-down period, along with 4 muscle toning exercises using dumbbells or resistance bands, two exercises to improve balance, one yoga sequence, and one exercise of their choice. To maintain interest, a new group of exercises was introduced every three weeks. They were encouraged to become familiar with the new exercises during week one of each phase, and then increase the intensity with either greater weight/resistance or more repetitions during weeks two and three.

Their program completion rate was 81% (n=145). Five of the participants were excluded because they did not attend the 6-month MRI session. An additional 8 were excluded because they did not attend the 12-month MRI session. Finally, 12 more were excluded because they had excessive head motion in the MRI that created inaccurate results. Thus, a final group of 120 participants had complete MRI data from all three measurement sessions and were included in the statistical analyses.

The researchers predicted that one year of moderate-intensity physical activity performed three days per week would increase the size of the hippocampus and that the change in hippocampal volume would be associated with improved memory function and increased serum BDNF. The results of the study were that the moderate-intensity aerobic exercise training group had an increase in the size of their anterior hippocampus and improvements in spatial memory. The hippocampal volume of the aerobic exercise participants increased by approximately 2%, which the researchers stated was effectively reversing age-related loss in volume by 1 to 2 years. They found that the hippocampal volume decreased in the stretching and toning control group, but a higher pre-intervention fitness partially attenuated the decline, suggesting that fitness protects against volume loss. Overall, they concluded that the results of their study demonstrated that aerobic exercise training was effective at reversing hippocampal volume loss in late adulthood, which was accompanied by improved memory function.

 

1. Encyclopaedia Britannica. Hippocampus: brain. https://www.britannica.com/science/hippocampus
2. Erickson K I, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proc. Natl. Acad. Sci. U.S.A. 2011;108(7):3017–3022. doi: 10.1073/pnas.1015950108. Epub 2011 Jan 31.