"When awareness is separate and distinct from vrittis - mental modifications, when waking, dream, and deep sleep pass like clouds, yet awareness of Atman remains, that is the experience of total relaxation...That is why, in Tantra, YogaNidra is the doorway to samadhi!"

Neuro-physiologic Basis: 

There is no question about the close relation between the body and the brain. Various centers in the brain control, modify, and affect our bodily functions. In fact, there is a center in the brain for every act, whether willful or reflex, physical or mental. Experimental data have identified many such specific centers. Stimulation of these centers leads to appropriate action, be it motor, sensory, secretary, or emotive, affective, or cognitive. Thus we have a holographic representation of body on the brain.

To put the thing more concretely, it is proved that the left half of the body is represented in right half of the brain and vice-a-versa. As far as the muscular actions are concerned, the representation is in an 'upside down manner' in motor area of pre-central gurus. Thus, at the top of this part of brain the lowest portion of our body - foot - is represented. Then comes ankle, leg (calf), knee, thigh, hip, trunk, shoulder, arm, elbow, wrist, palm, fingers, thumb, then neck, jaw, face, eyes, ears, tongue, taste, swallowing, etc. The same thing is applicable for sensations. Stimulation of brain-centers of sensory cortex evokes sensations on the opposite half of the body. 

Yoga Nidra Practice: 

In Yoga Nidra exactly opposite process is used to make the brain centers active by focusing awareness on the parts of the body in a definite sequence. Thus, the person tries to stimulate various parts of the brain by focusing the awareness on the corresponding parts of the body. By awareness is meant 'attitude of witness' towards physical or mental actions of the body. 

The Technique 

The procedure is carried out by first doing a few asanas- practicing a few postures. Then the person lies on his or her back in totally relaxed posture (Shavasana - posture simulating dead body). Eyes are lightly closed, arms are kept with palms facing upwards and fingers are half lifted from the ground, breathing is natural and quiet.

Resolve or Sankalpa:

Before the rotation of awareness the aspirant should make a positive resolve about the aim in life. The wordings should be clear and precise. It is not expected that the sadhaka makes minor resolves like, 'I will give up smoking, or drinking, or tobacco, but he or she should think higher. A few resolves are:

• I will awaken my spiritual potential
• I will be successful in my all undertakings,
• I will achieve total health
• I will a positive help in spiritual progress of others, etc.

Rotation of Awareness 

Then the rotation of awareness begins. Patient has to just visualize the part of the body mentioned by the instructor, be that a teacher or a tape-recorder. The student must not move any part of his body. Quickly corresponding with the instructions, he or she has to shift his or her awareness from one part to the next. The aspirant should not imagine the next part before the instructor mentions it. The whole process is a pleasure and not a burden. There should not be any anxiety or expectation. The usual pattern is to start focusing awareness in the following sequence: 

First on the right side, thumb, fingers (one by one), palm of the hand, then the wrist, the forearm, the elbow, arm, shoulder, right back, hip, thigh, knee, leg, ankle, foot, great toe, other toes of the right foot. The same sequence is repeated for the left side. 

Then awareness is focused on the proximity of body with the carpet (ground). Back of the head, shoulders, back and spine, thighs, heel. Next the front of the body surface is brought in to awareness: Face, brow, eyes, nose, lips, mouth, chin, neck, chest, abdomen, upper thighs, legs, foot, and toes, in that order. 

Awareness of the Breath 

After rotation of the consciousness in such a sequence, focusing attention on the act of breathing completes physical relaxation. One simply maintains awareness of breath, either at the nostril or of its passage through the navel and throat. It is claimed that the process, in addition to concentration, assists pratyahara from the subtle body in subsequent processes. 

Feelings and Emotions 

Next comes relaxation at the level of feelings and emotions. Attempt is made to bring to memory the intense physical and emotional feelings; they are re-experienced or re-lived, and then effaced. Usually this is practiced with pairs of two opposite feelings like hot and cold, lightness and heaviness, pain and pleasure, joy and sorrow, etc. Relaxation at the emotional level and building up of strong willpower is the major outcome of this procedure. 

Visualization 

The final stage of Yoga Nidra relates to mental relaxation. The aspirant tries to visualize the objects as described by the instructor. Usually such images and symbols are chosen that have universal significance. To quote a few symbols: mountain, river, ocean, temple, church, cross, saint, flower etc. The practice helps to develop self-awareness and helps in concentration or dharana. Rarely, evendhyana may be the natural outcome. 

Ending the Practice

Once again the resolve or sankalpa is intently thought of or even visualized. Thus, consciously one tries to direct the unconscious mind about the goal in life. This time the unconscious is very receptive and therefore, may accept the suggestion from the conscious mind with more intensity. It is claimed that in due course of time, depending upon the sincerity and regularity of the sadhaka, the resolve bears fruit in sadhaka's life. 

Utility 

Yoga Nidra helps in restoring mental, emotional, and physical health by way of relaxation, and makes the mind more conducive to pratyahara, dharana, and meditation. Such a practice helps harmonize two hemispheres of the brain and the two aspects of autonomous nervous system viz. sympathetic and parasympathetic. The impressions in the subconscious are brought to surface, experienced and removed. Thus, the fixation of awareness to the body is replaced with awareness linked with subtler aspects of prana and spiritual dimensions.