Elsevier

Ageing Research Reviews

Volume 20, March 2015, Pages 37-45
Ageing Research Reviews

Review
Lifelong brain health is a lifelong challenge: From evolutionary principles to empirical evidence

https://doi.org/10.1016/j.arr.2014.12.011Get rights and content

Highlights

  • Exercise, fasting and intellectual challenges improve brain function.

  • Energetic challenges stimulate synaptic plasticity and neurogenesis.

  • Intermittent challenges may protect the brain against injury and disease.

  • Society-wide changes will be required to implement brain-healthy lifestyles.

Abstract

Although the human brain is exceptional in size and information processing capabilities, it is similar to other mammals with regard to the factors that promote its optimal performance. Three such factors are the challenges of physical exercise, food deprivation/fasting, and social/intellectual engagement. Because it evolved, in part, for success in seeking and acquiring food, the brain functions best when the individual is hungry and physically active, as typified by the hungry lion stalking and chasing its prey. Indeed, studies of animal models and human subjects demonstrate robust beneficial effects of regular exercise and intermittent energy restriction/fasting on cognitive function and mood, particularly in the contexts of aging and associated neurodegenerative disorders. Unfortunately, the agricultural revolution and the invention of effort-sparing technologies have resulted in a dramatic reduction or elimination of vigorous exercise and fasting, leaving only intellectual challenges to bolster brain function. In addition to disengaging beneficial adaptive responses in the brain, sedentary overindulgent lifestyles promote obesity, diabetes and cardiovascular disease, all of which may increase the risk of cognitive impairment and Alzheimer's disease. It is therefore important to embrace the reality of the requirements for exercise, intermittent fasting and critical thinking for optimal brain health throughout life, and to recognize the dire consequences for our aging population of failing to implement such brain-healthy lifestyles.

Section snippets

Evolutionary perspective: why ‘hunger games’ bolster brainpower

Animals in the wild, particularly carnivores, survive by being able to locate and acquire food. As a corollary, evolution favored those individuals and species that were adept at outsmarting their prey and their competitors in the struggle for limited food sources. The brain is therefore geared for a high level of motivation and optimal sensory-motor and cognitive function when the individual experiences hunger/food scarcity, and the often vigorous exercise required to obtain food (Fig. 1; and

Empirical findings demonstrate that exercise, energy restriction and intellectual enrichment enhance neuroplasticity

Laboratory rats and mice are usually fed ad libitum and so eat as much and as often as desired. In addition, they are typically maintained in small cages with no running wheels or other opportunities for exercise. Moreover, each cage usually contains 4 or 5 animals, which is a relatively small social group. Thus, it is reasonable to consider control laboratory animals as ‘couch potatoes’ that, compared to rodents in the wild, are sedentary, overeat and experience little cognitive stimulation (

Signaling pathways and molecular mechanisms

There is considerable overlap in cellular and molecular mechanisms by which the challenges of exercise, energy restriction and intellectual enrichment enhance neuroplasticity and sustain cognitive performance during aging (Fig. 3). Three general mechanisms are: (1) increased synaptic activity resulting in the production and release of neurotrophic factors which then activate signaling pathways that stimulate the formation and plasticity of synapses, and neurogenesis; (2) activation of adaptive

Intermittent challenges may protect against neurodegenerative disorders

Epidemiological data suggest that individuals who exercise regularly during their adult life are at reduced risk of Alzheimer's and Parkinson's diseases. Population-based studies suggest that individuals who exercise in midlife are less likely to develop dementia later in life (Geda et al., 2010). Consistent with the possibility that regular exercise protects against Alzheimer's disease are data showing that midlife cardiorespiratory fitness is associated with a lower risk of dementia (Defina

Implications for a brain-healthy society

Advances in agriculture, food processing and transportation have contributed to a decline in the exposure of individuals in modern societies to the two major energetic challenges that sustain optimal brain health, namely, intermittent food deprivation/fasting and vigorous daily exercise. While many continue to engage in intellectual challenges that can enhance cognitive function, the available evidence suggests that such intellectual challenges are insufficient to mitigate age-related

Acknowledgements

This work was supported by the Intramural Research Program of the National Institute on Aging, and the Glenn Foundation for Medical Research.

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