Invisible multi-luminaire 40 Hz flicker does not entrain human electroencephalography

BackgroundMulti-luminaire light stimulation is a novel technique based on luminance flicker with low modulation depth created by two spatially adjacent light sources aimed to deliver 40 Hz neural stimulation while reducing discomfort, offering potential non-pharmacological, noninvasive, and in-home interventions for Alzheimer's disease and dementia. However, these cognitive effects have never been validated with electroencephalography (EEG).ObjectiveIn this study we aim to assess the ability of multi-luminaire light stimulation to evoke a 40 Hz EEG response under two conditions: direct viewing and indirect viewing.MethodsThe M + BrainCare light by Delta Electronics was used in this study. Participants were stimulated either directly by looking at the light (direct viewing condition), or off of the reflection from a piece of paper to mimic everyday reading (indirect viewing condition). EEG power at 40 Hz from these conditions were compared to a positive control of 40 Hz luminance flicker with 100% modulation depth (stroboscopic flicker).ResultsIn both multi-luminaire conditions, there was no significant 40 Hz EEG oscillations. In contrast, stroboscopic control elicited robust entrainment in all participants, propagating to frontal regions.ConclusionsOur results question the efficacy of multi-luminaire technology, specifically the Delta M + BrainCare light, for evoking 40 Hz neural responses. Future studies involving multi-luminaire technology should pay special attention to EEG validation prior to making claims about neural oscillation and brain health.