October 26, 2020

The effects of regular aerobic exercise on hippocampal structure and function

Engaging in regular exercise has numerous benefits for brain health. In particular, a number of studies have associated exercise with improvements to the structure and function of the hippocampus, especially in older adults. This region plays a critical role in memory function, and is altered in a number of psychiatric disorders associated with memory impairments (e.g. depression and schizophrenia), as well as healthy ageing. Thus, exercise may provide an effective method of enhancing / ameliorating hippocampal integrity; however, an improved understanding of exercise-related effects in young to middle-aged adults is required. We assessed the effects of regular exercise and cardiorespiratory fitness on hippocampal structure and function in young to middle-aged adults. We recruited a sample of 40 healthy adults, comprised of individuals who self-reported as engaging in high (regular exercisers) or low (sedentary) levels of physical activity (PA) according to World Health Organisation guidelines (high PA n=20; low PA n=20). A multi-modal assessment of hippocampal structure and function was conducted using structural magnetic resonance imaging (sMRI), magnetic resonance (MR) spectroscopy, and hippocampal-dependent memory tasks. We observed evidence of increased N-acetyl-aspartate (NAA) concentration and associative memory performance in high PA individuals. However, no differences in hippocampal volume or pattern separation capacity were observed between groups. We found that cardiorespiratory fitness was positively associated with (left, right, and bilateral) hippocampal volume, NAA concentration, and pattern separation, but not associative memory. Therefore, we provide evidence that engaging in higher levels of exercise has demonstrable benefits for hippocampal integrity and function. Given that young and middle-aged adults are overrepresented in the diagnosis of psychiatric illnesses which affect hippocampal integrity (e.g. depression and schizophrenia), it is possible that exercise may provide a low-risk, effective method of remediating this dysfunction.

 bioRxiv Subject Collection: Neuroscience

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