Biofeedback, Yoga and Altered States of Consciousness

Swami Tapasmurti Saraswati

Understanding of the experience of meditation and other so called 'altered states of consciousness' has been greatly enhanced by the use of biofeedback instrumentation in recent years. The following analysis is based on information made available by G. G. Blundell and C. M. Cade in the books 'Self Awareness and ESR' and 'EEG Measurement'.

These two British research workers specialize in the area of biofeedback and its use as both a therapeutic tool and a means of developing altered states of consciousness. By combining the results of autonomic nervous system response and brainwave patterns, they have been able to provide a useful 'map' of the experience of meditation and paranormal phenomena. This research gives an interesting insight into how yogic techniques can induce these experiences, and the relationships which exist between these various patterns of consciousness.

Biofeedback instruments

The information was obtained from experiments using two instruments, the electrical skin resistance meter (ESR) and the electroencephalogram (EEG).

The first device, the ESR meter, indicates the level of bodily arousal or relaxation in response to changes in autonomic activity, indicated by varying skin resistance in the palm of the hand. The EEG device, also known as the 'mind mirror', measures the brain's electrical activity in both hemispheres simultaneously. Both instruments measure different psycho-physiological parameters, and we will see that their complementary use adds a further dimension to this area of research.

The biofeedback principle

We understand our voluntary nervous system as that part of the nervous system directing the skeletal muscles which we can consciously control. The involuntary or autonomic nervous system was previously believed unable to respond to conscious control. However, yoga and biofeedback are showing that conscious control of involuntary functions is also possible. The first step of both yoga and biofeedback training is to increase self-awareness and then the next step is to develop the controlling abilities.

Blundell describes the biofeedback principle as follows: 'If through the use of some device, one can become aware of an internal event of which one is not normally aware, e.g. the production of alpha rhythms in one's brain, then one can learn to control some aspect of that event.' This principle speaks for itself in its relation to the use of biofeedback as an aid to the development of higher states of awareness.

Arousal and relaxation responses

The ESR meter measures changes in the autonomic nervous system from arousal, described as the 'fight or flight' response, to relaxation, described as the relaxation response. It should be understood that the relaxation response is not a reduction in activity in the nervous system; rather it is an increase in activity in the parasympathetic nervous system, just as arousal is an increase in activity in the sympathetic nervous system. Our 'normal' waking state can be considered as halfway between the extremes of arousal and relaxation.

The measurement of arousal and relaxation on the ESR meter is indicated by the scale shown below.

Fig. 1 ESR Meter Scale
Lesh Scale ↓ Needle at central or starting position
6 5 4 3 2 1 0          
0     10     20 30   40   50 micro amps
Relaxation Normal Arousal
← Increasing Skin Resistence

The scale is graduated from 0 to 50 micro amps, indicating the current flowing during the measurement of skin resistance. Arousal is indicated by more current (decreased skin resistance), relaxation by less (increased skin resistance). We can conceptualise this process by imagining that as we withdraw our awareness more and more from the external environment, the body's response is to create a protective 'shield' of the skin layers by increasing 'resistance' to outside interference. The middle of the scale (25 micro amps) is used as the starting point for tests of relaxation and arousal. In these tests, the needle of the ESR meter moves to either the right (arousal) or the left (relaxation), indicating the autonomic response. Although this description of the meter and its scales has been simplified, it is sufficient for an understanding of the processes described in this article.


The EEG device, or 'mind mirror', measures brainwave activity by placing electrodes at various points on the scalp. The person monitoring the device has an instantaneous and overall view of the brainwave patterns indicated by panel lights showing amplitude and frequency of brainwaves in both hemispheres of the brain.

In order to proceed further with this discussion, we will need to understand a little more about what the brain rhythms mean.

  • Beta: 13-30 cycles/sec. This frequency is associated with our normal waking state of thinking, problem solving, and externalised awareness.
  • Alpha: 8-13 cycles/sec. for adults, 4-7 cycles/sec. in children. Alpha frequencies indicate a state where the mind is becoming empty and receptive. They can usually be produced only with the eyes closed, and they signal the beginning stages of meditation.
  • Theta: 4-7 cycles/sec. This is associated with drowsiness, inspiration, deep meditation and access to the unconscious mind.
  • Delta: 0.5-4 cycles / sec. This frequency is associated with deep sleep and paranormal phenomena.

The Lesh scale

The boxes numbered 0-6 on the top of the ESR meter scale are known as the Lesh scale, and concern only the relaxation response, i.e. the 0-25 micro amp range.

Dr Terry Lesh of the University of Oregon (USA) found that subjective experiences described by meditators often occurred in definite patterns. C. M. Cade and Dr G. Wolley-Hart successfully correlated these 'Lesh' states with changes in skin resistance and EEG patterns during relaxation and meditation, resulting in Table 1. The Lesh scale is a description of experiences, although there is no clear cut demarcation between each state of consciousness.

The Lesh states and their corresponding ESR and EEG readings show that as we relax more, the frequency of brainwaves decreases and the subjective sensations become more lucid, until in state 6 a state of deep insight is experienced.

Lesh states and yoga nidra

It is interesting to compare the states described in Table 1 with the practice of yoga nidra. In the table, the experiences described range in sequence from beginning to relax, going into relaxation with many thoughts and memories, bodily sensations, vivid awareness of breath, heartbeat, other sensations, then moving into a deeply satisfying experience with a clear and new insight.

In yoga nidra the sequence of instructions proceeds from initial relaxation to awareness of sounds, to rotation of consciousness through the body, to awareness of bodily sensations (heat, cold, heaviness, lightness, etc.) to breath awareness and finally to visualization sequences. It could be said that this sequence enables the practitioner to rapidly move through the distracting states of 0 to 2, by using the rotation of consciousness and awareness of bodily sensations to induce state 3. Breath awareness corresponds to state 4, and visualization, when the mind has become calm and clear, induces states 5 and 6. The correlation between the yoga nidra practice and the subjective Lesh states is quite remarkable.

Table 1: Lesh States
    Relaxation response  
Lesh No. Description of the states micro amos % change EEG rhythm
0 Beginning to relax, maybe difficulty in stilling the mind. 'Why am I doing this?' 25-20 below 25% Intermittent alpha and beta.
1 Dizziness, befogged consciousness, feeling like going under an anaesthetic, everyday affairs fill the mind, unfocused attention. 20-16 25% -35% Reduced beta; continuous alpha.
2 Calmness, relaxation. Childhood and other scenes from the past recalled. 16-13 35% - 45% No beta, continuous alpha, intermittent theta.
3 Well defined state. Pleasant bodily sensations of floating, lightness, rocking, swaying. More sustained concentration. Increased and clearer imagery. 13-10 45%-55% Continuous alpha with falling frequency; almost continuous theta.
4 Vivid awareness of breath, heartbeat. Effortless concentration. Feeling of bodily expansion (full of air). 10-8 60% - 70% Continuous alpha; theta falling in frequency.
5 Very lucid state. Deep, intense alertness, calmness and detachment. Feeling of altered state lacking in levels 0-4. 8-5 70% - 80% Continuous theta; alpha almost at theta levels.
6 New way of feeling. Intuitive insight. Understanding from a new level of awareness. Synthesis of opposites into a higher unity. below 4 Over 80% Little activity except for occasional delta.