Quality Assessment And Neurophysiological Signal Resemblance Of Ear EEG

Electroencephalography (EEG) is a non-invasive tool for recording brain activity, typically using scalp electrodes. Ear EEG offers an alternative by leveraging the ear canal's proximity to the brain. This study evaluates the quality of signals from Ear EEG devices compared to traditional scalp and intracranial EEG. The Emory Prime Dataset, collected from 2019 to 2021 at Emory University Hospital, includes 1,255 hours of simultaneous ear EEG and clinical EEG (intracranial (n=9) or scalp (n=11) from 20 patients. Three ear EEG channels were recorded: channel 1 (right ear canal to left concha cymba), channel 2 (left ear canal to left concha cymba), and channel 3 (right canal to left canal). One hour of awake and one hour of sleep data were randomly selected per patient. Artifacts were visually identified, and signal quality was assessed using the autoreject algorithm. Quality scores for ear EEG and scalp EEG were compared for both awake and sleep segments. Signal comparisons included spectral parameter correlations and coherence analysis between ear EEG, scalp EEG, and intracranial EEG. Results showed better ear EEG quality during sleep than wakefulness, due to reduced movement and muscle activity. During sleep, ear EEG quality surpassed neighboring temporal scalp EEG channels and matched non-temporal scalp channels. Contralateral ear EEG resembled contralateral temporal scalp EEG more than unilateral configurations. Coherence between ear EEG and intracranial EEG was higher for electrodes near the brain surface, especially in delta, theta, and alpha frequencies. In conclusion, contralateral ear EEG during sleep provides quality comparable to scalp EEG and closely mirrors intracranial EEG activity, particularly in lower frequency bands associated with global brain processes.