Alpha enhancement, autonomic activation, and extraversion.

Autonomic activation as reflected by heart rate, skin conductance, muscle tension, and T-wave amplitude of the electrocardiogram were registered during biofeedback training of EEG alpha. The group of 25 subjects showed significant enhancement of alpha but no systematic change in autonomic activation. This result was interpreted as supporting Eysenck's theory of two feedback loops for mediating cortical arousal. According to this theory, autonomic changes would not be expected to accompany changes in cortical arousal during resting conditions lacking emotional content and, therefore, not involving the visceral brain. Although some of the subjects who succeeded in increasing alpha experienced it as positive and others as strenuous, alpha change did not correlate significantly either with the dimension of extraversion, or with those of locus of control and neuroticism.