Some factors in the feedback control of human alpha rhythm.

Abstract

A series of studies were conducted to explore various factors that might be involved in the biofeedback control of human alpha rhythm. Subjects were given either auditory or visual feedback regarding the occurrence of alpha activity in their electroencephalographic record. Additional subjects were run as a noncontingent feedback control group. Significant linear increases in alpha density across feedback trials were observed in all subjects given visual feedback, including the noncontingent control group. Auditory feedback, on the other hand, did not lead to significant increases in alpha density across feedback trials, and levels approached, but did not exceed the initial pre-experimental baseline levels. The data of these experiments do not support the view that the feedback situation produces levels of alpha activity greater than those seen under natural baseline conditions or that accurate feedback is necessary to demonstrate gradual trial to trial increases in this rhythm. The data do suggest that alpha densities observed in the feedback situation have less to do with feedback per se or a learning process than with the experimental situation and Ss' own natural alpha densities. The results support the position that increases in human alpha activity occur in feedback situations when the individual disinhibits various stimulus, attentional and arousal factors that normally block this rhythm.