Electrocortical, autonomic, and subjective responses to rhythmic audio-visual stimulation

The present study was designed to test the hypothesis that varying sensory input can affect mood, autonomic arousal, and electrocortical activity. Twenty right-handed males were exposed to three rhythmic audio-visual stimulation programs, with either a high intensity and variety of stimuli (program H), a low stimulation (program L) or with a transient from high to low (program HL). Multichannel EEG, heart rate, and skin conductance were recorded continuously, and after each trial mood was rated on a bipolar adjective list. EEG data were subjected to FFT dipole approximation procedure, and dipole locations and field strength (Global Field Power) were analyzed for the frequency bands theta, alpha, and beta 1. Mood ratings clearly differed between programs H and HL, with highest values of arousal after H. Programs L and HL decreased autonomic arousal, whereas H induced deactivating as well as activating effects. Field strength of the alpha band decreased similarly during all programs. Dipole sources were located more to the left in the alpha band and more to the right in the beta 1 band during all programs as compared with baseline. Therefore, programs affected mood and autonomic variables differently, but not electrocortical variables. The higher activation of the right hemisphere during all programs is interpreted as an indication that audio-visual stimulation does induce changes in the brain, such as are commonly found in altered states of consciousness.