Dual-light invisible 40 Hz flicker does not entrain human EEG

Invisible flicker stimulation (IFS) aim to deliver 40-Hz neural entrainment while eliminating discomfort, offering potential non-pharmacological, noninvasive, and in-home interventions for Alzheimer’s and dementia. However, these cognitive effects have never been validated with EEG. We assessed the M+ BrainCare light's ability to induce 40-Hz EEG entrainment under three conditions: direct IFS-viewing, indirect IFS-viewing, and stroboscopic control. In both IFS conditions, there was no significant 40-Hz EEG oscillations. In contrast, stroboscopic control elicited robust entrainment in all participants, propagating to frontal regions. These results question the neural efficacy of current IFS technologies, emphasizing the need for EEG validation in future studies.