A recent review article in NPJ Aging has highlighted that studies testing auditory gamma stimulation, a non-invasive neuromodulation technique that has shown some promise in cognitive decline, show mixed results which is likely due to different methods and choice of outcome measures. Auditory gamma stimulation means playing sound pulses at a gamma frequency (the frequency of the fastest, most active brain waves) to gently nudge the brain’s activity to synchronize with that rhythm. It is usually delivered by short clicks or tones through headsets and is considered low risk. In animal studies, it has been shown to change brain activity, resulting in some improvements in cognition and biological pathways.
This review of 62 studies exploring auditory gamma stimulation in people with cognitive impairments and healthy individuals found that mixed results have been reported across studies. The authors searched through 3754 articles and included 62 studies in their review that involved 2179 people. They then extracted information about how the study was conducted and compared and contrasted this to work out why variable results have been reported so far. Key items that the authors found were: 1) individual differences (sex, age, other psychosocial factors) affected responses to the therapy; 2) clinical differences (like cognitive decline and disease stage) affected responses to the therapy; 3) cognitive and biological effects varied and 4) no optimal therapeutic ‘dose’ could be ascertained as studies have tested fixed and personalised levels. In mild cognitive impairment and Alzheimer’s disease, the results across studies were very variable. Across all of the studies, some adverse events were reported including headache, dizziness and tinnitus.
The authors concluded that it is important establish more consistent terminology and methods ahead of new studies, as this will help interpret results and might enable research that combines results (meta-analysis). The authors made several recommendations for moving forward including generating consensus on metrics being reported and standardizing outcome measures. It would also be important to include studies of the long-term effects as these are currently unknown.
More information on this study is available here: https://www.nature.com/articles/s41514-025-00305-1
