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Sensory gamma frequency stimulation in cognitively healthy and AD individuals safely induces highly coordinated 40 hz neural oscillation: A preliminary study of non‐invasive sensory stimulation for treating Alzheimer’s disease
Journal article   Open access   Peer reviewed

Sensory gamma frequency stimulation in cognitively healthy and AD individuals safely induces highly coordinated 40 hz neural oscillation: A preliminary study of non‐invasive sensory stimulation for treating Alzheimer’s disease

Ho‐Jun Suk, Diane Chan, Brennan Jackson, Vanesa Fernandez, Danielle Stark, Noah Milman, Sara Beach, Brandt Uitermarkt, Phillip Gander, Aaron D Boes, …
Alzheimer's & dementia, Vol.16(S7), e041146
12/2020
DOI: 10.1002/alz.041146
url
https://doi.org/10.1002/alz.041146View
Published (Version of record) Open Access

Abstract

Background Our lab previously showed that 40 Hz sensory stimulation can modulate neural oscillations, ameliorate Alzheimer’s disease (AD) pathology, and improve cognition in AD mouse models (Iaccarino, Singer et al., Nature, 2016; Martorell, Paulson et al., Cell, 2019; Adaikkan et al., Neuron, 2019). To determine the safety and feasibility of 40 Hz sensory stimulation as a potential therapeutic for AD, human subjects, including AD patients, were exposed to various stimulation modalities and their electrophysiological responses were studied. Method We developed a device that delivers light and sound at desired frequencies for human use. Cognitively healthy (24 males, 22 females; age range 20‐75) and AD subjects (7 males, 10 females; age range 55‐88) were stimulated with our device while their scalp electroencephalogram (EEG) was recorded. Epilepsy patients with intracranial electrodes (1 male, 1 female; age 19) were also exposed to our device for sensory stimulation while recording the intracranial EEG (iEEG). The EEG signals were screened for interictal/ictal spikes and analyzed to evaluate spectral characteristics. Result The EEG signals from cognitively healthy and AD subjects as well as epilepsy patients did not show any interictal/ictal spikes during or after the stimulation. In all subject groups, our sensory stimulation increased the spectral power and coherence at 40 Hz, with the concurrent visual and auditory stimulation leading to more widespread and coordinated 40 Hz oscillations than visual or auditory stimulation alone. iEEG signals showed that our sensory stimulation can entrain deeper brain regions. An hour‐long continuous 40 Hz stimulation using concurrent visual and auditory stimuli in healthy older subjects showed 40 Hz power and coherence both increasing over time. Following the hour‐long stimulation, gamma power and coherence were elevated compared to the pre‐stimulation levels. Conclusion Our non‐invasive sensory stimulation at gamma frequency safely induces highly coordinated 40 Hz oscillations in cognitively healthy and AD subjects. This serves as a preliminary study for a placebo‐controlled, randomized control trial to test the effect of our sensory stimulation on AD. The application of non‐invasive techniques to modulate gamma oscillations in the human brain is a novel and potentially very powerful disease modifying therapeutic for the treatment of dementia.

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