The effects of alpha (10 Hertz) and beta (22 Hertz) audiovisual stimulation on EEG entrainment: Individual baseline differences are critical to prediction of effects

Claims have been made for the clinical effects of "entrainment" stimulation, yet there are virtually no systematic studies employing postentrainment baselines and using typical equipment presently available. This report was designed to partly remedy this missing information. Two groups of normal college students were formed: One (the alpha group; n = 13) received 10-hertz audiovisual (AV) stimulation for 8 minutes, and the other (beta; n = 12) group received 22-hertz AV stimulation for 8 minutes. EEC power and magnitude in the alpha and beta bands were FFT-extracted before, during, and for 24 minutes after stimulation. Baseline (prestimulation) alpha and beta power predict (p < .05) the effects of stimulation, leading to individual differences in responsivity. High-baseline alpha subjects showed either no entrainment or prolonged entrainment with alpha stimulation. Low-baseline subjects showed transient entrainment. Baseline alpha also predicted the direction of change in alpha with beta stimulation. Baseline beta and alpha predicted beta band response to beta stimulation, which was transient enhancement in some subjects, inhibition in others. Some subjects showed prolonged beta enhancement with beta stimulation. Thus, a patient's EEG must be thoroughly studied prior to implementation of an entrainment regimen, lest the EEG effect obtained be opposite to that desired. The older "photic driving" literature supports this view.