Boy, was Descartes wrong. His philosophy of duality divided our being into two distinct substances: a holy soul and a mortal carcass. The soul was the source of reason, science and everything nice. Our flesh, on the other hand, was “clocklike,” just a machine that bleeds. With this schism, Descartes condemned the body to a life of subservience, a power plant for the brain’s light bulbs.
One of the great themes of modern neuroscience is that Descartes was utterly wrong. (I discuss this theme in my Walt Whitman chapter of Proust Was A Neuroscientist. Whitman’s mantra, after all, was that “the body is the soul and the soul is the body”.) The mind and flesh are profoundly entangled, knotted together into a single homeostatic machine.
This is the subject of an excellent new book, from Sandra and Matthew Blakeslee, The Body Has a Mind of Its Own. The book is ostensibly about the body maps in the somatosensory cortex, but it really explores the full range of somatic cognition, from phantom limbs to the intentionality of the premotor cortex.
The book is also full of wonderfully practical digressions:
The soles of your feet have touch receptors that send signals up to your brain every time you stand and put pressure on the ground. These signals are combined in higher brain maps and vestibular, visual and other touch information to keep you nimble on your toes.
But these foot signals can blur as receptors become less sharp with age. Diabetes and poor blood flow can deaden the foot. You begin to sway. But as James Collins, a biomedical engineer at Boston University, discovered, if you add a faint vibration to the bottom of the foot – he invented insoles that do just that – your brain will automatically pick up degraded signals from your feet. With his insoles, eighty-year-olds can stand as straight as thirty-year-olds.
You don’t necessarily need electronic gadgets to keep your vestibular system in tune, however. Walking on cobblestones is a low-tech, proven route to the same end. Studies in Europe have shown that balance deteriorates more slowly in elderly people who walk regularly on cobblestone than in those who use only modern sidewalks. The Chinese have known about this for centuries. Go to almost any park in any city in China, and you will find thousands of cobblestones laid out in lovely patterns on the ground. People take off their shoes and walk on the stones to achieve better health.