Your Brain Is Only As Old As You Think It Is

June 28, 2019

Ten years ago, right after I delivered a speech on innovation to the top tier of executives at a Fortune 100 company, one of the executives sought me out with a compliment. “Gee, Eric you haven’t lost a step at all.”

The executive, in his forties, had known me for a couple of decades—and what he really meant was that, in my late fifties, I hadn’t slowed down mentally nearly as much as he expected I would.

Now in my late sixties, every other week or so, I experience this sort of attitude from people of all ages with comments like “Wow, you’re still doing that?!” or, more subtly and insidiously, having my opinion discounted because of my age. For example, I have “aged off’ a few technology advisory boards on which I served.

So, yeah, I’m not happy about age bias—but is it at all grounded in reality? Do we lose a step, or two, or three as the decades accumulate?

Reality vs. Myths of Brain Aging

Let’s address that question by starting with some of the latest neuroscience on brain aging, and there is some good news.

Whereas brain scientists used to think we lost about 1 percent of our brain cells every year after our late 20’s, it turns out these estimates were based on methodological errors (e.g. failing to account for brain shrinkage as opposed to neuron loss, over the inclusion of dementia patients in samples, etc.). Current estimates are that healthy brains lose only about 4 percent of neurons by the time they get to their 70’s and 80’s.

The conventional wisdom that we don’t replace dead neurons with new ones as we age has also proven incorrect; for example, the hippocampus (important to forming memories) of even elderly people grows new neurons from scratch all the time.

Finally, the brain retains its plasticity well into old age—growing, like an exercised muscle, with mental and physical exercise. For instance, older subjects taught to juggle showed increases in the volume of motor cerebral cortex (coincidentally, this physical exercise also increased cognitive function).

So that’s the good news.

The other side of the story is that, on average the speed of cognition, including reaction time, does slow down in healthy brains as they age, and as we get older we generally have a harder time “inhibiting” (tuning out distractions while we concentrate). So on average, we don’t get “dumber” as we age—but numerous replicated studies reveal we do take longer to be as smart as we always were and we have a harder time concentrating.

Questioning Even the “Hard Facts” on Cognitive Slowing

Although the research demonstrating cognitive slowing and age-related deficits is quite solid, I question the true cause of such declines, and whether they are completely inevitable.

Take tuning out distractions as a case in point. A study by Dr. Arthur Shimamura and colleagues at UC Berkeley, that compared the ability of young adults and senior professors, to tune out distractions showed that senior professors, but not age-matched non-professors, were just as good at tuning out distractions as young adults.

But a control group in the study made up of seniors who were not professors performed worse on tuning out distractions than either senior professors or young adults. The authors interpreted these findings to mean that senior professors kept their brains young by staying much more mentally active than elderly non-professors.

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