A Wearable EEG System for Closed-Loop Neuromodulation of High-Frequency Sleep-Related Oscillations (original) (raw)

Objective. In healthy sleepers, cortical alpha oscillations are present during the transition from wakefulness to sleep, and then dissipate at sleep onset. For individuals with insomnia, alpha power is elevated during the wake-sleep transition and can persist throughout the night. Neuromodulation techniques using phase-locked auditory stimulation to augment or suppress oscillations have been put forth as alternatives to drugs for improving sleep quality. This approach has been applied to slow oscillations present during deep sleep, but due to technical limitations in signal readout it has not been tested on faster frequency alpha oscillations. Approach. Here we examine the feasibility of using an endpoint-corrected version of the Hilbert Transform (ecHT) algorithm implemented efficiently on-device to measure alpha phase and deliver phase-locked stimulation in the form of pink noise sound bursts to modulate ongoing alpha oscillations and promote healthy sleep initiation. First, the ecHT algorithm is implemented on a tabletop electroencephalogram (EEG) device and used to measure the timing of the auditory evoked response and its delivery at precise phases of the alpha oscillation. Secondly, a pilot at-home study tests feasibility to use a headband wearable version of the neuromodulation device for real-time phase-locked stimulation in the alpha (8-12 Hz) frequency range. Main Results. Auditory stimulation was delivered at the intended phases of the alpha oscillation with high precision, and alpha oscillations were affected differently by stimuli delivered at opposing phases.Our wearable system was capable of measuring sleep micro-and macro-events present in the EEG that were appropriate for clinical sleep scoring during the at-home study. Moreover, sleep onset latencies were reduced for a subset of subjects displaying sleep onset insomnia symptoms in the stimulation condition. Significance. This study demonstrates the feasibility of closed-loop real-time tracking and neuromodulation of alpha oscillations using a wearable EEG device. Preliminary results suggest that this approach could be used to accelerate sleep initiation in individuals with objective insomnia symptoms.