Yoga Nidra and the Brain
Modern neurophysiologists have been able to demonstrate an obvious relationship between the body and the brain which was first recognized by the ancient yogis thousands of years ago. Using stimulating electrodes to probe the brains surface, neurosurgeons have shown that each part of the body is precisely mapped out along the surface of the central gyrus or fold of the sensory motor cortex of the brain. Researchers have named this neuronal map or hologram of the physical body the motor homunculus (little man) - the symbolic man lying within the brain matter.
There is a link between the body and brain through the sensory motor cortex. The sensory motor cortex is the region of the cerebral cortex where nerve cells are engaged in planning and directing the actions of muscles and glands that are under conscious control. All the body parts through which the awareness passes during rotation of consciousness can be located there, for example: "Right hand thumb, second finger, third finger, fourth finger, fifth finger, palm of the hand, back of the hand, wrist, elbow, shoulder, armpit, right side, right waist, right thigh, kneecap, calf muscle, ankle, heel, sole, big toe, second toe, third toe, fourth toe, fifth toe..." This is where we make the connection between the latest neurosurgery and the meditation technique of yoga nidra.
Yoga nidra the rotation of consciousness does begin at the right hand thumb as beginning with the hands affects a huge area of the brain. During yoga nidra it is relatively easy to develop mental awareness of the hands. The hands are also among the most sensitive of man's organs of action, with a greater number of nerve endings in the palms and fingers to transmit messages to the brain. If you have ever practised this technique, you will recognize the signposts on the sensory-motor cortex as precisely those parts of the body through which your awareness passes during rotation of consciousness in yoga nidra. The brain is the physical mediator of consciousness, linking mind, body and emotions into one harmonious unit.
The neurosurgeon affects the body by stimulating the brain. The practitioner of yoga nidra begins at the other end of the nerve pathway by heightening the awareness of the body in order to stimulate the brain. The progressive movement of awareness through the parts of the body not only induces physical relaxation but also relaxes the sensory-motor cortex of the brain and clears all the nerve pathways to the brain, both those governing the physical activity and those concerned with incoming information. At the same time we make a total run through the brain surface, from inside out. In this way yoga nidra relaxes the mind by relaxes the body.
Now we can begin to understand why the precise order of rotation of consciousness throughout the body parts is so important in the practice of yoga nidra. Once this sequence is established it should not be altered, as it induces a flow of pranic energy within the neuronal circuit of the motor homunculus. This flow is accompanied by a subjective experience of relaxation, release or letting go as spontaneous dissociation of consciousness from the sensory and motor channels of experience occurs. Familiarity and daily repetition of this sequence exerts a rapid inturning (inner) effect upon the normally fragmented and dissipated (worldy pleasures) awareness.
The systematic passage of awareness through the brain during yoga nidra is inseparable from the flow of both nervous and pranic energy. As well as clearing old pathways, every time one practices yoga nidra this energy flow forges new connections between brain circuits, and lights up the dark, inactive areas of the brain. It is impossible to ignore the connection between the discoveries made by today's brain explorers and those made by the seers who long ago evolved the practice of yoga nidra.