Physical exercise habits correlate with gray matter volume of the hippocampus in healthy adult humans

Abstract

Physical activity facilitates neurogenesis of dentate cells in the rodent hippocampus, a brain region critical for memory formation and spatial representation. Recent findings in humans also suggest that aerobic exercise can lead to increased hippocampal volume and enhanced cognitive functioning in children and elderly adults. However, the association between physical activity and hippocampal volume during the period from early adulthood through middle age has not been effectively explored. Here, we correlated the number of minutes of self-reported exercise per week with gray matter volume of the hippocampus using voxel-based morphometry (VBM) in 61 healthy adults ranging from 18 to 45 years of age. After controlling for age, gender, and total brain volume, total minutes of weekly exercise correlated significantly with volume of the right hippocampus. Findings highlight the relationship between regular physical exercise and brain structure during early to middle adulthood.

Figure 1. Partial correlation plots showing the positive association between the residualized values for the mean number of minutes of exercise per week and the residualized modulated volume data extracted from each hippocampus after controlling for age and gender (*p < .05).

Figure 2. The figure shows the coronal (upper left), sagittal (upper right), and axial (lower left) slices highlighting the location of a cluster of 21 voxels within the right hippocampus (MNI: x = 27, y = −7, z = −21) where the tissue volume showed a significant correlation with the number of Minutes Per Week of exercise, after small volume correction for multiple comparisons (*p < .10, FWE).

For visualization purposes, the scatterplot (lower right) shows the significant association between the residualized values for the mean number of minutes of exercise per week and the mean extracted data from the significant cluster in the hippocampus after controlling for age and gender.

Figure 3

(a) The figure shows the spatial location of a large cluster of 1047 voxels where there was a significant association between the number of Minutes Per Week of exercise and the mean gray matter volume within the left posterior insula (MNI: x = −51, y = −21, z = 12; *p < .05 cluster corrected). The top three slices show the cluster in the coronal view and the bottom three slices show it in the axial view. (b) For illustrative purposes only, the scatterplot shows the linear association between the residualized number of Minutes Per Week of exercise and the mean gray matter volume within the left posterior insula cluster.

Figure 4. Axial views showing the left (red) and right (green) hippocampal regions of interest (ROIs) as defined by the Automated Anatomical Labeling (AAL) Atlas within in the Wake Forest University PickAtlas Utility for SPM8.