Distribution of 'criterion' alpha in the resting EEG: further argument against the use of an amplitude threshold in alpha biofeedback training.
The object of this study was to explore the relevance of an amplitude threshold for defining alpha in biofeedback studies. One of the lowest thresholds used in earlier studies (1.5 microV) was selected and the EEG base level of 94 subjects measured. Due to the importance of reinforcement rate in biofeedback, results were divided into three categories: under 25%, between 26-74%, and over 75% alpha. The results showed a positively skewed distribution with 68% of the subjects displaying under 25% alpha. The subjects' means on the control variables: anxiety, impulsivity, and monotony avoidance were within the range of normal and did not correlate with the amplitude categories. The conclusion drawn was that skewness is not the result of an abnormal sample but of an arbitrarily set amplitude criterion. On the basis of this data, an integrated alpha amplitude measure is advocated.
D000513:Alpha Rhythm; D001676:Biofeedback, Psychology; D003216:Conditioning, Operant; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male