Changes in the EEG Spectrum and Subjective Characteristics of the General State after Stimulation with Variable Frequency Photic Stimuli with Two Types of Organization

Two sinusoidal signals, one with a constant frequency of 13 Hz and the other with a frequency continuously changing from 1 to 6 Hz and back, were presented simultaneously to subjects through spectacles with light-emitting diodes either to both eyes as a product (amplitude modulation of a constant frequency by a variable one) or to each eye separately. Both kinds of variable frequency exposure revealed a rhomboid pattern of the resonance activation of the EEG spectrum, similar to the spectral dynamics of a signal subject to amplitude modulation. This testifies to the key role of EEG amplitude modulation in the responses of the nervous system to variable frequency rhythmic stimuli. Both types of photic stimulation led to a substantial increase in EEG spectral density and improved the subjects' self-rating of the overall state of well-being, activity, and mood. In addition, separate stimulation of each eye led to an improvement in the anxiety and exercise performance indices (the Luscher color test) and a significant correlation between the intensity of EEG responses and changes in the general state. These differences are explained in terms of the involvement of the interhemispheric interaction mechanisms in the processing of complex rhythmic signals by the brain.