Effects of physical exercise on the aging brain across imaging modalities: A meta-analysis of neuroimaging studies in randomized controlled trials.

BACKGROUND: Physical exercise is effective in protecting against age-related neurodegeneration and cognitive decline. Although there are many neuroimaging studies to evaluate the effect of physical exercise on aging brains, consistent conclusions are limited due to the wide variety of measuring techniques and small sample sizes. OBJECTIVE: Identify brain regions that show exercise-induced neuroplasticity consistently across various imaging modalities and correlate regional neuroplasticity with cognitive changes in older adults. METHODS: An electronic literature search for randomized controlled trials with magnetic resonance imaging measures was performed. We conducted a series of quantitative meta-analyses using activation likelihood estimation on included studies with voxel-based neuroimaging findings. Nonvoxelbased findings were summarized as a descriptive review. RESULTS: Out of 839 publications identified from the literature search, 30 experiments including 2670 participants from 22 papers met the criteria of meta-analyses. Overall, physical exercise consistently results in structural and functional changes in the hippocampus/parahippocampusl area and a cluster within the cerebellum. Although changes of medial/superior prefrontal cortex did not pass the stringent threshold, they were associated with cognitive changes. CONCLUSIONS: This study highlights the effectiveness of physical exercise in inducing hippocampus plasticity, which may be crucially relevant for maintaining memory function in older adults.