Does weak gamma entrainment still work? Rethinking the comfort-efficacy trade-off in 40 Hz sensory stimulation

As 40 Hz sensory stimulation gains attention as a potential treatment for Alzheimer's disease, comfort-focused designs such as invisible spectral flicker and multi-luminaire are increasingly used to promote long-term compliance. However, these systems often produce significantly weaker electroencephalographic entrainment than traditional stroboscopic lights. It is therefore important to question the common assumption that any level of entrainment is sufficient, and consider the possibility of nonlinear or threshold-based mechanisms that may require a minimum entrainment strength for therapeutic effects. The field needs to empirically test the relationship between entrainment strength and outcome, to ensure efficacy is not compromised for comfort.