Neural entrainment induced by periodic audiovisual stimulation: A large-sample EEG study

Stroboscopic or "flicker" stimulation is a form of periodic visual stimulation that induces geometric hallucinations through closed eyelids. While the visual effects of this form of sensory stimulation have received considerable attention, few studies have investigated the neural entrainment effects of periodic visual stimulation. Here, we introduce two variants of the classic flicker paradigm while recording EEG to study neural entrainment effects in a large sample (over 80 participants per condition). In the first condition, we used multimodal stimulation composed of two simultaneous visual strobe frequencies paired with binaural beats which provided auditory stimulation at roughly the same frequency as the slower strobe. We compared this condition to sham stimulation, in which both strobes were set to very low frequencies and in which the binaural beats were absent. Additionally, we compared both conditions to a control group in which participants focused on their breathing during eyes-closed meditation (no stimulation). Our results demonstrate powerful evidence of neural entrainment at the frequency of the slower strobe in the experimental condition. Moreover, our findings resemble effects reported in prior literature using conventional non-invasive techniques for electromagnetic brain stimulation. We argue that stroboscopic stimulation should be further developed along these lines, e.g., as a potential therapeutic technique in psychiatric disorders.