It is increasingly clear that what’s good of your body is also good for your brain, and regular exercise is no exception. Study after study supports this premise, consistently finding correlations between higher levels of physical activity and better brain ageing. Exercise has also emerged as a factor that may prevent (or at least delay) the onset of Alzheimer’s disease.
The healthy brain needs and craves physical activity
Exercise may in fact help offset one of the most common effects of ageing on the brain – the sort of generalised slow-down in neural processing that manifests as slower reaction times and taking longer to learn new information. Recent brain imaging studies show that highly fit older adults have faster reaction times than their less-fit counterparts, an indication of better concentration. They also are better able to focus on relevant information and ignore irrelevant cues, indications of better attention. These effects are “robust and relatively immediate” once an exercise programme has begun, according to Arthur Kramer, PhD, a neuroscientist at the University of Illinois at UrbanaChampaign, who is a leading expert in this area.
How much exercise? What kind?
How much exercise is necessary? Experts suggest 30 minutes or more at least three times a week. Brisk walking or any type of aerobic activity that increases cardiovascular fitness is beneficial, as are leisure activities that get us out and moving, like gardening or golf. Even better it seems, are physical activities that challenge the mind as well, such as learning a new dance, practicing Tai Chi, or taking up a new sport. This may be because learning a new skill activates new patterns of brain activity, and may literally build new synaptic connections in areas of the brain that correspond to the skill learned. Social activities such as dancing or group exercise classes may be especially beneficial because they combine social interaction with physical activity. The important thing is to do something; any amount or type of activity is better than being sedentary.
How does exercise affect the brain?
Accumulating evidence from neuroscience research is shedding new light on the basic question of how exercise changes the brain in beneficial ways. Exercise reduces grey matter loss: Highly fit people also show less of a decrease in grey matter in the cortex than is normally seen with ageing, which may suggest a protective effect of exercise against nerve cell death. This effect is most pronounced in areas of the brain involved in executive aspects of cognition, which typically decline most with ageing.
Exercise promotes neurogenesis:
Laboratory animals that are allowed to run freely on an exercise wheel show increases in the generation and survival of new neurons (neurogenesis) in the hippocampus, a brain structure involved in memory formation. The hippocampus is one of only a few distinct areas of the brain where neurogenesis has been proven to occur naturally.
The animals who had increased rates of neurogenesis in the hippocampus learned how to find their way through a maze more quickly than animals with normal rates of neurogenesis, suggesting that the increase in new neurons may be related to improved learning. These types of findings are now being extended to humans, and at least one brain imaging study has found that people involved in a consistent, regular aerobic exercise programme (roughly 40 minutes a day, five times a week) had a larger hippocampal structures after six weeks.
Exercise strengthens neural connections:
In laboratory animals, running increases the number and density of nerve connections (synapses), physically changing the structure of these nerve-signal pathways to make them more efficient at transmitting nerve signals. The animal evidence suggests that the act of running activates a specific gene to pump up production of a protein that seems to be crucial to the type of synaptic remodelling that has been observed. This same molecular mechanism, called long-term potentiation, is believed to underlie long-term memory formation.
Exercise changes gene activation patterns:
Human DNA contains about 30,000 genes, each of which can be turned on or off to produce (or stop producing) a wide array of proteins and enzymes that our cells use to conduct their daily business of keeping us alive and healthy. To understand how exercise may be effecting this complex system of gene activation, or “gene expression”, scientists have examined which genes are switched on or off in animals that exercise regularly. It turns out that exercise induces changes in the expression patterns of a slew of genes, some of which become more active (up-regulated) and some of which become less active (down-regulated). Many of the genes that are up-regulated are known to play roles in the structure and adaptability of synapses, suggesting a possible mechanism by which exercise can increase the complexity and flexibility of the brain.
Exercise pumps up growth factors:
Nerve growth factors (neurotrophins) play vital roles in nourishing and supporting brain cells. A growth factor, brain-derived neurotrophic factor (BDNF), increases significantly in the brains of animals that run voluntarily. BDNF is thought to be involved in gene regulation, neurogenesis and synaptic adaptability and there is evidence that BDNF stimulates new synapses in the hippocampus.
Exercise enhances blood flow:
The brain is the most energy hungry organ in the body. To function optimally, it needs lots of oxygen and glucose, which are provided by blood that circulates into the brain via arteries and capillaries. Exercise increases the density and size of brain capillaries, which in turn increases blood flow to the brain. This may in turn help support the survival of new neurons in the brain areas such as the hippocampus, which is involved in memory formation, and may facilitate faster “firing” by neurons.
The material on this page “Brain Health – Stay Active” has been used with the kind permission from the Dana Alliance for Brain Initiatives. www.dana.org/stayingsharp