An assessment of the effects of multi-session audio-visual stimulation on cognitive measures and the cortical EEG

The effects of multi-session (20 sessions) audio-visual stimulation (AVS) at the dominant alpha frequency and twice dominant alpha frequency on the EEG were investigated using thirty subjects. A pilot study provided preliminary data to predict the outcomes of multi-session AVS. An eyes-closed baseline EEG determined each subject's dominant alpha frequency. Ten subjects were stimulated for twenty minutes at their dominant alpha frequency, ten at twice their dominant alpha frequency, and ten subjects served as controls, receiving no stimulation. A post-session EEG was recorded two weeks after the AVS sessions ended. Power data were analyzed for 19 locations in six bandpasses using repeated-measures ANOVAs and appropriate post-hoc tests. Results indicate neither AVS condition affected the alpha bandpass. Alpha AVS showed within session effects on the beta 1 and beta 2 bandpasses, but no long-term effects. Beta AVS increased within-session power within the theta, beta 1, and beta 2 bandpasses, showing long-term effects at frontal locations within the beta 1 bandpass. Exploratory analyses of eyes-open EEG data indicate that changes in power seen in the eyes-closed data do not persist when the eyes are open. Neither AVS condition showed effects on the cognitive tests employed in this study. These results are discussed in the context of neurofeedback.