Music-Synchronized Gamma Light Stimulation Strengthens Theta-Gamma Coupling in Older Adults with Cognitive Impairment: Results from a Randomized Feasibility Trial

Noninvasive clinical innovations for restoring gamma activity via sound and light stimulation have the potential to improve memory and cognitive abilities in Alzheimer's disease. We assessed whether pairing music with theta- and gamma-band light changes memory-supporting neural dynamics, and whether those changes track cognition. In an ongoing randomized feasibility trial, 38 older adults with cognitive impairment completed eight weeks of an audiovisual intervention. The treatment group (n = 19) listened to self-selected music while viewing light stimulation that consisted of a 39-Hz gamma-band signal modulated by delta- and theta-band musical rhythms. The control group (n = 19) listened to podcasts while viewing synchronized lights without the gamma frequency (delta-band only). Before and after the 8-week intervention, participants completed a face-name association task and the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog). Individuals in the treatment group showed significant improvements on a face-name association task and the ADAS-Cog. Cluster-based permutation testing showed a larger increase in phase-amplitude coupling between acoustic theta phase and frontal EEG gamma amplitude in the treatment group compared to the control group. Across participants, increases in stimulus-driven theta to EEG-gamma phase-amplitude coupling were associated with improvements in memory. These preliminary results suggest that theta-gamma stimulation delivered through music and lights strengthens cross-frequency coupling, and may correspondingly strengthen associative memory.