By electronically feeding back to a subject information about his psychophysiological variables of which he would ordinarily be unaware, it is possible for the subject to learn to control these variables. Thus, electroencephalographic alpha states can be produced at will, complete muscle relaxation can be achieved, and control of skin temperature can be exercised when the appropriately recorded variable is fed back to the subject. Implications of this for psychiatric treatment are discussed, especially in the treatment of specific psychosomatic diseases and in the treatment of anxiety states associated with muscle tension.
Gaarder K, Chase C. Control of States of ConsciousnessII. Attainment Through External Feedback Augmenting Control of Psychophysiological Variables. Arch Gen Psychiatry. 1971;25(5):436-441. doi:10.1001/archpsyc.1971.01750170052009