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Research demonstrates that the brain’s cognitive abilities, structure and functioning change throughout life, and late adulthood represents an important turning point in the brain’s health. Indeed, after 65 years of age, the brain decreases in white and grey matter volume, neurotransmitter production, and synaptic connectivity. These changes are also reflected in reduced cognitive functions and mental abilities. However, research shows that exercise can be a powerful ally in preserving the brain’s health, functioning and structure. This article explores some research papers providing robust evidence of the beneficial effects of exercise on the brain in late adulthood.
Colcombe & Kramer (2003): Fitness effects on the cognitive functions of older adults: A Meta-Analytic Study
The authors of this study conducted a meta-analysis on eighteen longitudinal studies, to examine whether aerobic training enhances cognitive functions of healthy but sedentary older adults. This scientific endeavour was motivated by the lack of common consensus in human research on the effects of training interventions on the brain. The authors attribute the inconsistency of results to the differences in the theoretical and methodological positions on cognition adopted by different studies. Four theoretical positions on cognition were identified: speed hypothesis, visuospatial hypothesis, controlled-processing hypothesis, and executive-control hypothesis (by Colcombe&Kramer).
The method adopted by the authors consisted of coding the eighteen studies based on:
– theoretical variables: each study was independently coded by task, mapping them against the four theoretical positions (e.g. if the task involved finger tapping or reaction time the authors assigned it to the category speed hypothesis)
– participants’ characteristics: average age, gender, normal or clinical population
– characteristics of the training interventions: aerobic training or combination of cardio and strength exercises, duration of sessions and of intervention program, and amount of cardiovascular improvement shown by participants.
Overall, the results of this study showed that fitness training increased brain performance – with the greatest benefits for cognitive functions. Interestingly, the authors discovered some moderating effects of the type of fitness training, program duration, and training-session duration (e.g. brief training programs provided at least as many benefits as moderate training, but not as much as long-term training programs), and concluded that these factors should be further examined in future interventions studies.
Erickson et al. (2011): Exercise training increases size of hippocampus and improves memory
In this study, 120 older adults (55-80 years old) were randomly assigned to receive either moderate-intensity aerobic exercise 3 days a week or stretching and toning exercises that served as a control; the duration of both training interventions was 1 year. Magnetic resonance images were collected before the intervention, after 6 months, and after the completion of the program.
The findings of this research supported the hypothesis that aerobic exercise is neuroprotective:
– Aerobic exercise intervention increased anterior hippocampal volume by 2%, whereas the control group demonstrated a 1.4% decline in hippocampal volume over the 1-year period. Because hippocampal volume shrinks 1–2% annually, a 2% increase in hippocampal volume is equivalent to adding between 1 and 2 years’ worth of volume to the hippocampus. Since neurons in anterior hippocampus are associated with spatial memory and show greater age-related atrophy compared to posterior hippocampal cells, the authors suggested that aerobic exercise might be particularly beneficial for brain regions more susceptible to decline.
– The aerobic exercise group showed a 7.78% improvement in maximal oxygen consumption (VO2 max) after the intervention; a remarkable improvement compared to the control group. Moreover, it was found that larger changes in fitness translated to larger changes in hippocampal volume, and that improvements in VO2 max were correlated with increases in both anterior and posterior hippocampal regions.
– Aerobic exercise-induced increases in serum BDNF (brain-derived neurotrophic factor) were associated with greater increases in volume for the left and right anterior hippocampus. BDNF plays a crucial role as it mediates neurogenesis in the hippocampus enhancing memory and learning.
– It was observed that higher aerobic fitness levels at baseline and after intervention were associated with better memory performance. Also, larger left and right hippocampi at baseline and after intervention were associated with better memory performance. So, the researchers hypothesized and confirmed that in the aerobic exercise group, increased hippocampal volume was directly related to improvements in memory performance.
Cotman & Berchtold (2002): Exercise: a behavioural intervention to enhance brain health and plasticity
This study demonstrated that exercise enhances brain plasticity and overall health at molecular, cellular and structural levels. The main findings were:
– The authors paralleled results of animal research with human exercise studies finding that exercise strongly increased BDNF which supports memory, learning, and synaptic plasticity. The researchers hypothesized that exercise-induced increases in BDNF levels would be restricted to motor-sensory systems of the brain. Surprisingly, the results showed that BDNF levels increased in the hippocampus.
– BDNF gene expression in the hippocampus is controlled by neuronal activity and interactions between neurotransmitters (such as GABA, ACh – acetylcholine, and monoamines). Glutamate is the main pathway for BDNF gene expression, and it is modulated by interacting neurotransmitters. ACh maintains normal BDNF levels at rest, while during exercise GABA is crucial in combination with ACh and other chemical signals. Monoamines, especially if combined with antidepressant drugs, also significantly increase BDNF.
– BDNF changes induced by exercise are mediated also by peripheral mechanisms. Exercise increases IGF-1 (insulin-like growth factor) that enters the brain from the bloodstream. IGF-1 acts as an upstream regulator of BDNF: it triggers a chain of signals increasing the production of BDNF to protect, support and grow brain cells. Moreover, exercise raises levels of FGF-2 (fibroblast growth factor 2) in support cells in the hippocampus, which helps new brain cells grow and differentiate.
– Exercise activates several factors working together to increase neurogenesis, especially in the hippocampus, and protects the brain from stress and injury.
-Exercise, learning, and enriched environments (such as stimulating surroundings or rehabilitation training) produce similar effects in the brain. They all increase growth factors, promote the formation of new neurons, and cause structural changes in brain circuits.
In conclusion, exercise is a non-pharmacological intervention which supports and protects the aging brain and enhances plasticity. This article explored just some of the several research papers investigating the rejuvenating effects of exercise on the brain’s overall health and paving the way for future studies on the exercise-induced brain changes in late adulthood. Glossary:
– Meta-analysis: a quantitative technique for synthesizing the results of multiple studies of a phenomenon into a single result.
– Longitudinal study: the study of a variable or group of variables in the same cases or participants over a period of time, sometimes several years.
– Neurotrophin/neurotrophic factor: any of various proteins that promote the development and survival of specific populations of neurons.
– BDNF (brain-derived neurotrophic factor): a neurotrophin thought to be important in regulating synaptic plasticity, neurogenesis, and neuronal survival.
– VO2 max: VO2 max is defined as the maximum rate of oxygen consumption during intense exercise. It reflects the efficiency of the cardiovascular and respiratory systems in delivering oxygen to the muscles.
– Neurotransmitters – GABA, ACh (acetylcholine), monoamines (noradrenaline): any of a large number of chemicals that can be released by neurons to mediate transmission of nerve signals across the junctions (synapses) between neurons.
-Growth factor: a substance, such as a vitamin or hormone, which is required for the stimulation of growth in living cells.
– IGF-1 (Insulin-like growth factor): a protein made by the body that stimulates the growth, proliferation and differentiation of many types of cells
– FGF-2 (Fibroblast growth factor 2): a protein or neurotrophic factor which stimulates the growth and differentiation in multiple tissues
Sofia Nelam Singh
References
Cotman C, Berchtold N
Exercise: a behavioral intervention to enhance brain health and plasticity
Trends in Neurosciences, 25, 295-301
K.I. Erickson, M.W. Voss, R.S. Prakash, C. Basak, A. Szabo, L. Chaddock, J.S. Kim, S. Heo, H. Alves, S.M. White, T.R. Wojcicki, E. Mailey, V.J. Vieira, S.A. Martin, B.D. Pence, J.A. Woods, E. McAuley, & A.F. Kramer, Exercise training increases size of hippocampus and improves memory, Proc. Natl. Acad. Sci. U.S.A. 108 (7) 3017-3022, https://doi.org/10.1073/pnas.1015950108 (2011).
Colcombe, S., & Kramer, A. F. (2003). Fitness Effects on the Cognitive Function of Older Adults: A Meta-Analytic Study: A Meta-Analytic Study. Psychological Science, 14(2), 125-130.
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/vo2-max
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