Exercise Adapts the Aging Brain for Cognitive Health

Scientists are still trying to figure out exactly why exercise promotes cognitive health, especially in older adults. Some researchers posit that physical activity helps maintain youthful brain structures, but a new study instead suggests exercise changes the way seniors’ brains process information – making the aging brain more adaptable. Understanding how this adaptation occurs can ultimately guide seniors as they work to maintain good mental health.

“Although our cognitive ability will inevitably decline with age, we do have control over the rate of our decline,” says Jennifer Heisz of the Physical Activity Centre of Excellence at McMaster University in Canada. “Specifically, through a program of regular physical exercise, older adults are able to maintain optimal cognitive health for longer.”

As we move from childhood to adulthood, the complexity of our brain activity increases, boosting our capacity to process information. This complexity then starts to reduce in healthy older adults, but it is not a uniform reduction: while long-range brain communication, or “distributed processing,” decreases, local information processing increases.

Heisz and her colleagues wanted to test whether that shift might be an adaption to help older adults’ cognition and whether exercise assists in that adaptation. They used a technique called “multiscale entropy” to analyze the brain activity of seniors while they performed a challenging computer game that tested their ability to focus their attention and ignore distractions.

As published in the Journal of Cognitive Neuroscience, they found that older adults who were physically active had a more unique pattern of brain signal complexity – showing greater local processing of information – than both younger adults and their less-active peers. And, Heisz says, that unique pattern was associated with better performance on the task.

The results suggest that the shift from distributed to local processing that happens when we age is a healthy adaption for cognition, and that exercise helps to enable that “plasticity” in the brain. Heisz discussed with CNS these results and their implications, including sharing some guidelines for exercise as we age.

CNS: What are the advantages of local information processing compared to distributed information processing in older adults? Why is this shift necessary for better cognition?

Heisz: Aging is associated with many structural brain changes including the loss of myelin that is critical for distributed processing. An older brain that continues to rely on distributed processing may experience processing delays, which could impair cognition. In contrast, an older brain that functionally adapts to rely more on local processing may perform at high cognitive levels but be doing so through a fundamentally different way of processing information. And physical activity may be a key way to facilitate that shift.

CNS: Were you surprised by any of the results? What were you most excited to find in your results?

Heisz: I was both surprised and excited by the results. I had originally thought that physically active older adults would have a similar pattern of brain signal complexity to that of younger adults but instead their complexity pattern was much different. This is exciting because it suggests that physical activity is supporting cognition by facilitating neuroplasticity rather than helping the brain to remain more youth-like in the way it processes information.

CNS: How does your work differ from, or fit in with, past work on exercise and the aging brain?

Heisz: Recent attempts to uncover potential mechanisms underlying exercise-cognition interactions have focused on preserved youth-like neural structure and function in physically active older adults; however, these studies have been unable to convincingly link neural preservation in advancing age with the cognitive benefits associated with physical activity. Our study points to novel mechanism through which physical activity may change the aging brain to support aspects of cognition: Critically, the proposed mechanism does not preserve youthful-like brain function but rather facilitates functional reorganization of neural network processing to accommodate the infrastructure of an aging neural system.

CNS: Why do you think that physical activity better adapts older adults to local information processing?

Heisz: Physical activity seems to act as a catalyst that increases the fundamental components for neuroplasticity including enhanced “neurogenesis,” “synaptogenesis,” “angiogenesis” and “neurotrophic” factors – effectively priming the brain for change. This may be especially critical in an aging brain where these components are normally low. For older adults, functional reorganization may be difficult to achieve without the promotion of neuroplasticity through external factors such as physical activity. Consequently, older individuals who lack the necessary supplements for plasticity will continue to process information as they did prior to age-related neural degeneration, even if that way has become suboptimal.

CNS: What is the significance of your findings for the general population? Are you yet able to offer any specific recommendations regarding optimal amounts of exercise for younger and older adults?

Heisz: The message for the general population is that exercise is not only good for your body it is good for your brain too! Of course, everyone knows that exercise is good for the body yet the majority of older adults are still not sufficiently active for good health. My hope is that the promotion of physical activity for brain health will be the motivation that people need to become more physically active.

Although we do not have enough evidence to prescribe a specific exercise program for brain health, we do have guidelines for physical health (also see this toolkit). The recommendation for physical health is 150 minutes per week of moderate to vigorous physical activity. Although this may seem like a lot, an individual can accumulate their minutes over the week in bouts of 10 minutes or more.

CNS: What’s next for this work? What do you ultimately hope to accomplish?

Heisz: The ultimate goal of my research is to develop physical activity guidelines for total brain and body health.

If a physician were to ask me today what type of exercise she should prescribe for a patient with Alzheimer’s, the honest answer is: we really don’t know. My research program aims to fill in this knowledge gap to establish exercise guidelines to promote cognition function in seniors.

Understanding how exercise improves cognition is a complex question and there are many things to determine. For example, what aspects of cognition will benefit from exercise? How does exercise change the brain to support cognition? And when is exercise most effective at promoting cognitive health?

Working at the Physical Activity Centre of Excellence at McMaster University with seniors from the community, we are examining how different types of exercise – such as resistance training – impact memory and other key aspects of brain function, to develop prescriptions to be used in community-based exercise programs for seniors.

For an exercise program to be most effective, it needs to be implemented at a time when it can produce the greatest change. Alzheimer’s disease and related dementias are very slowly progressing diseases that can begin to damage the brain decades before any behavioral symptoms appear.

This temporal lag opens a window of opportunity for early detection and intervention. My lab will use EEG – a noninvasive neuroimaging tool that records brain signals – to identify neural biomarkers of cognitive decline so that we can intervene with prescribed exercise at a time that is most effective.

In the not too distant future, a physician could use EEG as part of a routine physical exam to screen for potential neural decline and accurately prescribe an exercise program to keep older adults both physically and mentally healthier for longer.

-Lisa M.P. Munoz