Finding equilibrium

DESPITE what M. Night Shyamalan says, the sixth sense has nothing to do with seeing dead people. According to veteran journalist Scott McCredie’s sporadically fascinating new book, the sixth sense is actually our sense of balance -- easy to take for granted, because it does not seem like a sense at all. In fact, it’s crucial to all sorts of normal human functioning, and when it’s out of whack (due to damage or deterioration or other insults), it can produce symptoms as scary as anything in a horror film.

Our sense of balance actually comprises three components: vision; our subconscious ability to “detect the movements of muscles and joints,” known as proprioception; and the vestibular system, or our inner ear, a mechanism so ingenious only nature could have devised it. The vestibular system is designed to inform the brain of our position in space. It does so through the movement of fluid in three semicircular canals, strategically positioned to map our head’s rotation in three dimensions (McCredie cleverly compares them to the roll, pitch and yaw of an airplane), which tell the brain how, and how fast, our heads are moving. Beneath these canals lie two sac-like structures containing bits of calcium carbonate -- yes, we really do have rocks in our heads -- that roll in accordance with linear acceleration or the force of gravity.

This vestibular system plays a starring role in that most common of balance-related maladies, motion sickness. (It turns out that motion sickness is not limited to humans -- even some species of fish get seasick.) The search for the causes of (and remedies for) motion sickness stretch back millenniums and have attracted such figures as Hippocrates, Sir Francis Drake and the psychologist and philosopher William James (who found that profoundly deaf people are immune to it). Once believed to be caused by overstimulation of our vestibular system, motion sickness has come to be understood in the last 40 years or so as the result of a conflict between visual and vestibular cues. McCredie uses the example of a World War II bomber crew: “The crew’s vestibular systems, sensing the jostling and motion of the plane, told them they were moving, while their eyes, seeing only the stationary interior of the fuselage, said they were still.” Pilots rarely reported motion sickness, because they could see the horizon, matching sets of information. “The same situation occurs on many family car vacations,” McCredie continues. “The driver rarely becomes motion sick, while kids reading in the back seat often do.”

McCredie doesn’t stop at motion sickness, however, taking us on a grand tour of our sixth sense. We meet acrobats and tightrope walkers; people whose vestibular systems are so damaged that they can barely function (according to some present-day doctors, Van Gogh may have been among them, perhaps explaining why, agonized by chronic dizziness and ringing in the ears, he performed his famous act of self-mutilation); and researchers who claim that improved balance skills can cure dyslexia. We learn that in humans the ear, and with it the vestibular system, is the first sensory organ to develop in utero, as a way to help orient the fetus when it is time to exit the womb; that John Kennedy Jr.’s fatal airplane crash was a classic case of what aviators call a “graveyard spiral,” induced when a pilot, flying with no visibility, depends on his vestibular system and winds up putting his craft into a fatal spin; and that a lack of a sophisticated balance sense may have hastened the demise of the Neanderthals.

As engrossing as much of this is, McCredie’s string-of-pearls approach to the subject creates its own kind of jostling. The lack of an overarching story line undermines narrative cohesion, so many of the chapters read like stand-alone articles, with the result that some concepts and characters get introduced more than once. Stylistically, McCredie is fond of journalistic shortcuts (like the kind of introductory clause best suited to a press release: “A sparkly ninety-two-year-old with a quick smile, Irene clung to a walker ... “) upsetting to that other inner ear.

Another element of the book’s narrative patchwork is a section in which the author alerts us to the growing threat of balance-related injuries in an aging America. As we live longer, all the components of our balance sense ebb: Our vision declines, the sense receptors in our proprioception system decay, and our vestibular system becomes less supple. We become increasingly off-balance, no doubt one of the main reasons for the rise in falls among the elderly. In fact, falls are the No. 1 cause of injury death for people over age 65.

McCredie conscientiously offers a list of activities that can bolster one’s equilibrium -- tai chi, strenuous walking, playing soccer or tennis, ballroom dancing, even gardening. He also includes an appendix of stork-like exercises that will either improve balance or ensure one a place in the Ministry of Silly Walks.

While there is no doubt that the health of the increasing ranks of older Americans poses a serious problem, McCredie’s prescriptions skirt a little too close to 11 o’clock news territory. “Balance” is at its best when it uncovers the strange and miraculous ways our brains and bodies collaborate -- and what can happen when they don’t. While the real sixth sense may not grant supernatural powers, its sensitivity and elegance make it no less of a marvel.