Balance: In Search of the Lost Sense by Scott McCredie
Little, Brown and Company, 2007, 296 pages
Paul E. Dennison
In this fascinating book, Scott McCredie discusses our amazing sense of balance, which most people take for granted. Our ability to move and function in gravity is a special gift that can be developed and better appreciated when we understand the physiology behind it. McCredie has done his research, and he covers the whole subject—from pilots to tightrope walkers to the equilibrium-challenged.
McCredie hypothesizes that the sense of balance is so essential to human survival and functioning that we’ve evolved with three distinct balance systems: the visual system for locating ourselves in space; the vestibular system of the inner ear for monitoring our head movement as we turn left and right; and the muscle proprioception system for continuous awareness of our body movement in space. The sense of balance depends on the interrelationship of these important systems. In the event that one is ever compromised, the other two will still provide the needed balance.
Most of us were introduced in school to the five senses: vision, hearing, touch, taste, and smell, yet we rarely stop to think how important these senses are in providing us with information. Sensory information is one of the first areas to fully develop in an infant’s brain. Without the ability to see, hear, touch, taste, and smell, we would be lost—unable to sense and, due to a lack of physical experience from which to develop ideas, also unable to think and learn.
The vestibular system supports the whole mind-body system, giving feedback about safety, stability, and the ability to actively function. This head-righting, labyrinthine system provides entry to the brain for all sensory experience. Physiologically, this system is connected to the digestive tract, the limbic system, the muscles of the eyes, and the language center of the brain,. A well-functioning vestibular system will thus contribute to such diverse elements as healthy digestion, emotional bonding, visual focus, and the emergence of receptive and expressive communication.
Located within the inner ear, the vestibular system is the first myelinated sensorimotor system of the human body, fully functional at birth. It’s made up of three semicircular canals and their related structures, which together comprise a navigation system for the three dimensions of movement: left-right, up-down, and forward-back.
The job of the vestibular system, then, is to sense changes in motion. It’s more of an accelerometer than a motion detector. The vestibular system senses both linear and rotational acceleration or deceleration of the head by the pull of gravity, it lets us know our position in space and whether we’re moving. Turning the head or spinning the body stimulates the release of serotonin, the “feel-good” hormone. Yet it stimulates the semicircular canals through such rotational movement also releasing a counterbalancing adrenaline for excitation and increased muscle tone. When there is sensory conflict and imbalance, the ability to read, write, communicate, and sustain attention is compromised. When these directions of rotational movements are integrated, in balance, and modulated, the individual can feel safe and can be open to new experiences.