Effects of Different Gamma-Stimulation Protocols on Brain Electrical Activity

Gamma-wave stimulation represents one of the most promising non-pharmacological approaches for enhancing cognitive function, which declines with aging and in neurodegenerative diseases. The aim of the present study was to identify optimal protocols for maximizing the effectiveness of gamma-wave stimulation. We investigated the effects of various combinations of physical and cognitive loads during visual gamma-wave stimulation at a frequency of 40 Hz using light of different wavelengths on the amplitude of gamma rhythms in the human brain. The effects were evaluated both at the level of individual EEG leads and across global brain electrical activity. The strongest response to visual gamma stimulation was observed in the occipital region. This effect exhibited a cumulative component, reflected by an increase in baseline activity at the stimulation frequency. The cumulative effect was most pronounced in the occipital and temporal regions. The magnitude of the gamma-stimulation response depended on the wavelength of the light stimulus and increased in the order of white, pink, and red. The most robust effect was observed with red-light stimulation combined with physical exercise. The influence of cognitive load was more prominent in the frontal and parietal regions of the brain.