Differentiation is easiest when the stimulus is smallest

Extract adapted from
The brain’s way of healing: Stories of remarkable recoveries and discoveries
By Norman Doidge MD Scribe Books

In Awareness Through Movement, Feldenkrais wrote,

If I raise an iron bar I shall not feel the difference if a fly either lights on it or leaves it. If, on the other hand I am holding a feather, I shall feel a distinct difference if the fly were to settle on it. The same applies to all the senses: hearing, sight, smell, taste, heat, and cold.”

If a sensory stimulus is very great (say, very loud music), we can notice a change in the level of that stimulus only if the change is quite significant. If the stimulus is small to begin with, then we can detect very small changes. (This phenomenon is called the Weber-Fechner law in physiology.) In his ATM classes, Feldenkrais instructed people to stimulate their senses with very tiny movements. These small stimuli radically increased their sensitivity, which ultimately translated into changes in their movements.

For example, Feldenkrais would ask people, as they lay on their backs, to tilt their heads very subtly up and down, about twenty times (or more), making the smallest possible movement – a hundredth of an inch – with as little effort as possible; they were to be aware only of the effect the movement had on the left side of the head, neck, shoulders, pelvis, and the rest of the left side of the body. Observing those changes will lead to decreased muscle tonus in the entire left side of the body (even though both sides of the body move when the head is tilted).

This change happens because the awareness itself helps reorganise the motor cortex and the nervous system. If the person were to scan his body before and after the exercise, he would discover that, mentally, the left side’s body image now feels lighter, also larger and longer and more relaxed, than the right side. (The cause is that the brain map for that side is now more differentiated and represents the body in finer detail. This technique of changing body tonus and brain maps is helpful because many movement problems often arise because areas of the body are not well represented in the brain maps.)