Liz, a woman in her mid-eighties, had two main problems.

Her first problem was low back pain and weakness in her legs – sure signs of spinal stenosis. In order to understand her diagnosis better, I timed her walking down the hallway in my office. It’s a pretty long hallway, but still, it took her nearly 40 seconds – way too long, if you ask me, even for a woman in her eighties.

What made her problem even more of a challenge was that six months previously she had had surgery that was supposed to help her stenosis.

Unfortunately, the surgery was largely ineffective. And the hours during which her brain was anesthetized left her with a second problem: severe deterioration of her memory.

So the first lesson I learned from my encounter with her is – surgery is never benign. I grant that sometimes it’s necessary, but if anesthesia is part of the surgical plan, even the most perfect surgery carries with it a significant risk of loss of brain function.

(My colleague the anesthesiologist says that the only patients at cognitive risk from anesthesia are those who already have signs of memory loss. I suppose the research statistics bear him out, but – call me a skeptic – to me that only means that even in a healthy person anesthesia taxes the brain, but most of us have enough reserve brain power to cope with the damage.)

Her memory loss created a challenge – making sure she consistently performed the therapeutic exercises needed to improve core strength and increase her walking speed. In fact, each time I saw Liz she told me that she had forgotten to practice her exercises.

But I was about to learn my second lesson.

Behind the scenes, her husband was coaching her to do her exercises every day, even though she didn’t remember doing them.

And sure enough, week by week I could see the clear improvement. Without realizing that she was undergoing a change, she soon was able to engage her abdominals correctly, stand without sagging her pelvis forward, balance on one foot for a little longer, and walk down my hall in under 30 seconds.

Through this experience I learned yet again how integral movement is to the brain.

The brain has been designed by evolution to enhance the performance of our body, not to “think.” What we think of as “memory” and “cognition” are only tiny teaspoonfuls artificially ladled from the thick soup of calculations the brain makes every second.