Investigating the Modulation of Spatio-Temporal and Oscillatory Power Dynamics by Perceptible and Non-perceptible Rhythmic Light Stimulation

Several studies emphasize the great potential of rhythmic light stimulation to evoke steady-state visual evoked potentials (SSVEPs) measured via electroencephalographic (EEG) recordings as a safe method to modulate brain activity. In the current study, we investigated visual event-related potentials (ERPs) and oscillatory power evoked by perceptible (above a previously estimated individual threshold) and non-perceptible (below the individual threshold) frequency-modulated rhythmic light stimulation at 10 Hz via a light-emitting diode. Furthermore, we examined the effect of overt and covert attention by asking participants to (1) directly focus on the light source (overt attention condition) and (2) indirectly attend it (covert attention condition). Our results revealed entrainment effects reflected in both ERPs and oscillatory power in the EEG even for a stimulation intensity below the individual perceptibility threshold and without directly fixating the light source. This non-invasive stimulation method shows strong potential for naturalistic non-clinical applications.