Variety Is the Spice of Brain Health

I think it is unlikely that he was referring to brain networks when, in 1785, William Cowper wrote in his poem The Task, "Variety is the very spice of life, That gives it all its flavor." At his time of writing, nobody knew that tissues were composed of cells and the foundational concept of neuroscience, the "neuron doctrine," was still almost a century away.

Cowper was really making the point that life is kind of boring if you just do the same things, and that change and variety of activities makes things interesting, just like spice brings out flavor in food. Despite that, Cowper was definitely onto something that is important for brain health over one's lifetime.

Keeping it fluid

The ability to solve new and complex problems declines steeply during healthy human aging. This "fluid intelligence" reflects and integrates function and performance across many domains and is thus a useful and important marker of brain health. It's been known for a while that fluid intelligence is related to activity in brain networks in the frontoparietal cortex. Damage to this region leads to impairment in fluid intelligence. But how does this relate to possible changes in fluid intelligence in aging?

Using fMRI along with clinical assessments and tests of fluid intelligence, questionnaires for physical activity, research from Cambridge University by Daniel Mitchell, Alexa Mousley, Meredith Shafto, and John Duncan used cohort data from the Cambridge Center for Ageing and Neuroscience to evaluate a relationship. Their study, published in The Journal of Neuroscience, highlighted that, "Despite consensus that fluid intelligence is associated with particular frontoparietal brain regions, little research has investigated suggestions that under-responsiveness of these regions mediates age-related decline." That is, they set out to examine a mechanistic and measurable link between brain activity and fluid intelligence itself.

Variety of activity is the spice of brain health

The main result of this analysis was that, "the variety of regular physical activities is the most important factor for maintenance of fluid intelligence in older adults." The group suggests that this may help develop "modifiable lifestyle factors that may help promote successful aging."

It is therefore possible that age-related functional differences in frontoparietal activity contribute to a reduction in fluid intelligence. This is an important mechanistic advance for future work given that, in their words, "global populations are living longer, driving urgency to understand age-related cognitive declines."

Be like water, my friend

The research is interesting for many reasons, not the least that the variety of physical activity seems to be the key factor, rather than the duration or frequency of the activity (which had a weaker association). This reminds me of the concept of "enriched environments" stimulating neuroplasticity and the robust nature of neuronal development. Here, the variety of physical activity is itself the enriched environment. Engaging in intellectually stimulating activities, those with social components, and physical activity are all beneficial for cognitive aging.

Along this line of thinking martial arts can be seen as an enriched activity across the lifespan, with potential results for healthy cognitive aging. Most traditional martial arts systems represent a constellation of collected activities. By their very nature, such traditional martial arts systems are already varied, including, amongst much more, fine and gross motor skills from long- to short-distance exchanges, full use of the entire body, multiple levels of thinking (from philosophical to functional), the use of different speeds of motion, partner work, and tools such as ancient weapons.

This suggestion of martial arts as therapy aligns well with some takeaways from the recent study. Their work concludes by saying the results "could provide a principle for designing activity-based interventions with a focus on variety, which may help older adults who are unable or unwilling to perform single, intensive physical activities. Increasing the variety of activities would represent a lifestyle modification that could be made relatively easily, regardless of specific interests or abilities."

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While Bruce Lee probably wasn't thinking about fluid intelligence when he said, "be like water, my friend," it's clearly a relevant idea for variety and adaptability. Spicing it up by keeping it interesting and varied regardless of age is the best advice.

(c) E. Paul Zehr (2023)