Physical activity is very important for a number of reasons – including that it helps to protect the structure and function of our brain as we age. This may be key in reducing the risk of developing certain neurodegenerative conditions, such as Alzheimer’s disease.
Though researchers have known about the protective effect of exercise for many years, exactly why it has this effect on the brain has remained a mystery. But a recent study published in the Journal of Neuroscience might shed some light on this puzzle. According to its findings, physical activity alters the activity of the brain’s immune cells, which lowers inflammation in the brain.
The brain contains a class of special immune cells known as microglia, which constantly survey the brain tissue for damage or infection, and clear away debris or dying cells. Microglia also help direct the production of new neurons (nerve cells in the brain which communicate and send messages to other cells) via a process called neurogenesis, which is linked with learning and memory.
But in order for microglia to step up and do their job, they need to switch from a resting state to an activated state. Signals from pathogens (such as a virus) or from damaged cells will activate the microglia. This changes their shape and causes them to produce pro-inflammatory molecules – allowing them to resolve and repair damage or infection.
However, microglia can also be inappropriately activated as we age, causing chronic brain inflammation and impairing neurogenesis. This inflammation has been suggested as a reason why brain function often declines with age, and these changes can be even worse in the case of neurodegenerative conditions such as Alzheimer’s.