Exercise training increases size of hippocampus and improves memory

Abstract

The hippocampus shrinks in late adulthood, leading to impaired memory and increased risk for dementia. Hippocampal and medial temporal lobe volumes are larger in higher-fit adults, and physical activity training increases hippocampal perfusion, but the extent to which aerobic exercise training can modify hippocampal volume in late adulthood remains unknown. Here we show, in a randomized controlled trial with 120 older adults, that aerobic exercise training increases the size of the anterior hippocampus, leading to improvements in spatial memory. Exercise training increased hippocampal volume by 2%, effectively reversing age-related loss in volume by 1 to 2 y. We also demonstrate that increased hippocampal volume is associated with greater serum levels of BDNF, a mediator of neurogenesis in the dentate gyrus. Hippocampal volume declined in the control group, but higher preintervention fitness partially attenuated the decline, suggesting that fitness protects against volume loss. Caudate nucleus and thalamus volumes were unaffected by the intervention. These theoretically important findings indicate that aerobic exercise training is effective at reversing hippocampal volume loss in late adulthood, which is accompanied by improved memory function.

Fig. 1.

(A) Example of hippocampus segmentation and graphs demonstrating an increase in hippocampus volume for the aerobic exercise group and a decrease in volume for the stretching control group. The Time × Group interaction was significant (P < 0.001) for both left and right regions. (B) Example of caudate nucleus segmentation and graphs demonstrating the changes in volume for both groups. Although the exercise group showed an attenuation of decline, this did not reach significance (both P > 0.10). (C) Example of thalamus segmentation and graph demonstrating the change in volume for both groups. None of the changes were significant for the thalamus. Error bars represent SEM.

Fig. 2.

The exercise group showed a selective increase in the anterior hippocampus and no change in the posterior hippocampus. See Table 2 for Means and SDs.

Fig. 3.

All scatterplots are of the aerobic exercise group only because it was the only group that showed an increase in volume across the intervention. (A and B) Scatterplots of the association between percent change in left and right hippocampus volume and percent change in aerobic fitness level from baseline to after intervention. (C and D) Scatterplots of percent change in left and right hippocampus volume and percent change in BDNF levels. (E and F) Scatterplots of percent change in left and right hippocampus and percent change in memory performance.

Fig. 4.

Flow diagram for the randomization and assessment sessions for both exercise and stretching control groups.

Fig. 5.

Display of the spatial memory task used in this study. The spatial memory task load was parametrically manipulated between one, two, or three items (two-item condition shown here). Participants were asked to remember the locations of one, two, or three black dots. After a brief delay, a red dot appeared, and participants were asked to respond whether the location of the red dot matched or did not match one of the locations of the previously shown black dots. This task was administered to all participants at baseline, after 6 mo, and again after completion of the intervention.