Many women over 40 experience some degree of brain lock, such as forgetting why we went upstairs or whom we were just about to phone. And though we may joke about it, we can’t help but wonder if these momentary mental glitches actually mean something dire—maybe early signs of age-related memory loss? And if so, is there anything we can do to keep them from getting worse?
For answers, More turned to John Medina, PhD, director of the Brain Center for Applied Learning Research at Seattle Pacific University, affiliate professor of bioengineering at the University of Washington in Seattle, and author of Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School.
Q | Do all human beings lose some brain capacity with age?
A | Most certainly. We all lose about 85,000 neurons a day. We can just kiss them good-bye.
Q | At what age does this decline in brain cells start?
A | We’re probably at our mental peak at 18 or 19 years old, at least for most of the cognitive performances that can be measured in the lab.
Q | What a waste of adulthood!
A | Well, in caveman days, humans didn’t live much past 23 or 24. We lived just long enough to be reproductively competent and to raise kids who could also reproduce. Which is why after age 40, we’re in genetic free fall in terms of aging. Sorry about that.
Q | How does the loss of neurons affect our ability to learn and to remember new information?
A | The effects still aren’t well-documented. But the answer to your question really depends on how we define memory. When a piece of information comes into your head, it goes through four separate processing steps, all of which you could call learning of a sort. The first step is encoding, in which information actually enters your brain through the senses: Light comes into your eyes, sound comes into your ears and so on. The second step is storage; once something gets encoded in your brain, what are you going to do with it? The third is retrieval, which is what most of us think of as memory: being able to get the information out again. Then comes the fourth and, I think, most important step, which is forgetting. Human learning is primarily subtractive. It’s controlled forgetting, learning how to forget in a smart enough way so that you can focus on what’s left in your cognitive landscape.
Q | Do we need to forget because we’re bombarded with so much information all the time?
A | Yes. The brain’s computational speed is pretty slow; it can’t process all the information that’s out there. So it has to make decisions about what it will and won’t take in. Figuring out what’s relevant and irrelevant, and then subtracting the irrelevant, is some of the most important work the human brain can do at any age.
Recently we’ve learned that most midlife memory fading isn’t about memory after all. That is, it’s not about retrieval mechanisms. It turns out that what middle-life brains have a really hard time doing is blocking out unnecessary information. As you get older, you lose your filtering ability.
A good example is not remembering where you put your keys. We sometimes call it a senior moment; it feels like you’ve forgotten something. But what’s actually happening is that lots of other input is flooding into your brain, and you’re unable to turn down that noise so that you can pay attention to the thing you’re trying to remember. As you begin to lose control of controlled forgetting, your ability to attend to things—like where you put your keys—decreases because you can’t prioritize your inputs.
Q | In your book you point out that there are significant genetic and anatomical differences between women’s brains and men’s. Does a woman’s ability to filter out information break down faster than a man’s?