Written by:  Shree Rath.

The effect of exercise on brain volume is a topic of growing interest in neuroscience and exercise science. Research indicates that regular physical activity, particularly aerobic exercise, can have a positive impact on brain structure, including changes in brain volume.

Studies have shown that aerobic exercise is associated with increased gray matter volume in various brain regions, including the hippocampus, prefrontal cortex, and motor cortex. These areas are involved in memory, learning, executive function, and motor skills. A 12 week supervised walking regimen saw an increase in the mean diffusivity in the insular cortex. Insula mainly aids in speech, and an increased performance was seen in the verbal fluency of the geriatric population. [1]. Another study quantified the physical exercise needed to increase gray matter volume in the hippocampus. It was seen that walking 72 blocks brought about a visible change in the volume, but further increase in activity didn’t necessarily correlate with an increased gray matter volume. This means, walking roughly 72 blocks or 6-9 miles per week helps to increase the functioning of the hippocampus, thereby decreasing the risk of cognitive decline [2]. Even normal household activity like tidying, shopping, etc have shown a positive association with hippocampal gray matter volume [3]. It is the number of minutes of workout, rather than the number of workouts that actually matters [4].

Exercise promotes neurogenesis, the formation of new neurons, in the hippocampus, a brain region critical for memory and spatial navigation. Additionally, exercise enhances synaptic plasticity, the ability of neurons to form new connections and strengthen existing ones, which is essential for learning and cognitive function. The main factor behind neurogenesis in the hippocampus is via BDNF or Brain derived Neurotropic Factor [5]. BDNF mediates cognitive performance in human, as evidenced by this study by Nicastri et al [6]. Across a 5 week intervention, BDNF was found to be positively correlated with cognition. Along with a diagnostic role, decrease in its levels have been noted to potentially cause dementia [7].

Regular exercise is also linked to improved white matter integrity, which refers to the structural integrity of the brain’s white matter fibers that facilitate communication between different brain regions. Enhanced white matter integrity is associated with faster information processing and better cognitive performance. A one year exercise intervention in a cohort found significant improvements in white matter integrity, thus enhancing short term memory [8].

So, why is this important for us? Brain volume has been shown to be significantly influencing the cognitive status. Brain volume and cognition are intricately linked, with larger brain volume, particularly in specific regions, associated with better cognitive performance. Overall brain volume correlates with enhanced cognitive function across domains such as memory, attention, and executive function, while age-related brain volume decline often accompanies cognitive declines [9]. Gray matter, containing neuronal cell bodies, is critical for information processing, and higher volumes in regions like the prefrontal cortex and hippocampus are associated with better executive function and memory [10]. White matter, composed of myelinated axons, facilitates communication between brain regions, and its integrity and volume are linked to cognitive abilities such as processing speed and working memory [11]. Regional brain volume variations also impact cognition; the prefrontal cortex supports executive functions, the hippocampus is crucial for memory and spatial navigation, and the parietal lobes are vital for spatial reasoning and attention [12]. Lifestyle factors like regular exercise, cognitive stimulation, and a healthy diet can help maintain brain volume and cognitive function, as exercise promotes neurogenesis and vascular health, cognitive activities enhance neuroplasticity, and a nutritious diet supports overall brain health [13]. Pathological changes, such as those from neurodegenerative diseases or traumatic brain injury, can significantly reduce brain volume and impair cognition [14]. Therefore, maintaining brain volume through various lifestyle interventions is crucial for preserving cognitive abilities throughout life.

In summary, regular exercise, particularly aerobic exercise, is associated with increased brain volume, enhanced neurogenesis, synaptic plasticity, improved white matter integrity, and higher levels of neurotrophic factors like BDNF. These changes contribute to better cognitive function, memory, and overall brain health, highlighting the importance of physical activity for maintaining optimal brain structure and function across the lifespan.

Disclaimer: Before starting any exercise program, it is important to consult with a qualified healthcare professional or physician to ensure that it is safe for you to do so, especially if you have any pre-existing medical conditions, injuries, or concerns about your health.

References:

[1] Won J, Nielson KA, Smith JC. Subjective Well-Being and Bilateral Anterior Insula Functional Connectivity After Exercise Intervention in Older Adults With Mild Cognitive Impairment. Frontiers in Neuroscience. 2022;16. doi:10.3389/fnins.2022.834816

[2] Erickson KI, Raji CA, Lopez OL, et al. Physical activity predicts gray matter volume in late adulthood. Neurology. 2010;75(16):1415-1422. doi:10.1212/wnl.0b013e3181f88359

[3] Koblinsky ND, Meusel LAC, Greenwood CE, Anderson ND. Household physical activity is positively associated with gray matter volume in older adults. BMC Geriatrics. 2021;21(1). doi:10.1186/s12877-021-02054-8

[4] Killgore WDS, Olson EA, Weber M. Physical Exercise Habits Correlate with Gray Matter Volume of the Hippocampus in Healthy Adult Humans. Scientific Reports. 2013;3(1). doi:10.1038/srep03457

[5] Liu PZ, Nusslock R. Exercise-Mediated neurogenesis in the hippocampus via BDNF. Frontiers in Neuroscience. 2018;12. doi:10.3389/fnins.2018.00052

[6] Nicastri CM, McFeeley BM, Simon SS, et al. BDNF mediates improvement in cognitive performance after computerized cognitive training in healthy older adults. Alzheimer’s & Dementia Translational Research & Clinical Interventions. 2022;8(1). doi:10.1002/trc2.12337

[7] Weinstein G, Beiser AS, Choi SH, et al. Serum Brain-Derived neurotrophic factor and the risk for dementia. JAMA Neurology. 2014;71(1):55. doi:10.1001/jamaneurol.2013.4781

[8] Voss MW, Heo S, Prakash RS, et al. The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: Results of a one‐year exercise intervention. Human Brain Mapping. 2012;34(11):2972-2985. doi:10.1002/hbm.22119

[9] Fjell AM, Walhovd KB, Fennema-Notestine C, et al. Brain atrophy in healthy aging is related to CSF levels of AΒ1-42. Cerebral Cortex. 2010;20(9):2069-2079. doi:10.1093/cercor/bhp279

[10] Hedden T, Gabrieli JDE. Insights into the ageing mind: a view from cognitive neuroscience. Nature Reviews Neuroscience. 2004;5(2):87-96. doi:10.1038/nrn1323

[11] Charlton RA, Barrick TR, McIntyre DJ, et al. White matter damage on diffusion tensor imaging correlates with age-related cognitive decline. Neurology. 2006;66(2):217-222. doi:10.1212/01.wnl.0000194256.15247.83

[12] Dhamala E, Jamison KW, Jaywant A, Dennis S, Kuceyeski A. Distinct functional and structural connections predict crystallised and fluid cognition in healthy adults. Human Brain Mapping. 2021;42(10):3102-3118. doi:10.1002/hbm.25420

[13]  Van Praag H. Exercise and the brain: something to chew on. Trends in Neurosciences. 2009;32(5):283-290. doi:10.1016/j.tins.2008.12.007

[14] Sharp DJ, Scott G, Leech R. Network dysfunction after traumatic brain injury. Nature Reviews Neurology. 2014;10(3):156-166. doi:10.1038/nrneurol.2014.15