Gamma Band Light Stimulation in Human Case Studies: Groundwork for Potential Alzheimer's Disease Treatment

Abstract

Background: It is known that proteins associated with Alzheimer's disease (AD) pathogenesis are significantly reduced by 40Hz entrainment in mice. If this were to translate to humans, verifying that such a light stimulus can induce a 40Hz entrainment response in humans and harnessing insights from these case studies could be one step in the development of a multisensory device to prevent and treat AD. Objective: Verify the inducement of a 40Hz response in the human brain by a 40Hz light stimulus and obtain insights that could potentially aid in the development of a multisensory device for the prevention and treatment of AD. Methods: Electroencephalographic brain activity was recorded simultaneously with application of stimulus at different frequencies and intensities. Power spectral densities were analyzed. Results: Entrainment to visual stimuli occurred with the largest response at 40Hz. The high intensity 40Hz stimulus caused widespread entrainment. The number of electrodes demonstrating entrainment increased with increasing light intensity. Largest amplitudes for the high intensity 40Hz stimulus were consistently found at the primary visual cortex. There was a harmonic effect at double the frequency for the 40Hz stimulus. An eyes-open protocol caused more entrainment than an eyes-closed protocol. Conclusion: It was possible to induce widespread entrainment using a 40Hz light stimulus in this sample cohort. Insights gleaned from these case studies could potentially aid in the development of a multisensory medical device to prevent and treat AD.