Assessment of Consciousness States with NextSense Ear Bud Devices

The goal of this study is to determine the feasibility in continuing to explore NextSense's ear-EEG device (EEGBud) and Ellcie Healthy glasses as wireless, wearable alternatives to the expense, discomfort, and burden in conventional surface electrodes and hardwired signal amplification for assessing consciousness states such as wake from sleep.

Detection of physiological parameters that define wake and various stages of sleep for clinical and research purposes has for decades relied upon systems that acquire physiological signals by way of multiple surface electrodes conveyed via conductive wires to hardware that amplifies and stores information on a central processing unit (CPU). This restricts or burdens human subjects in such a way that free action or movement is difficult and requires that patients be monitored by trained staff in an accredited sleep laboratory which levies substantial financial cost, can be inconvenient for patients and families, and is labor intensive. Visual scoring of the sleep stages is the gold standard in sleep research and medicine. Sleep scoring is performed visually based on the following signals: (1) electrical activity of the brain assessed via electroencephalogram (EEG), (2) electrical activity resulting from the movement of the eyes and eyelids assessed via electrooculogram (EOG) and (3) muscle tone recorded under the chin (submental) assessed via electromyogram (EMG). Scoring is usually performed according to standardized scoring rules: Rechtschaffen and Kales or the AASM. An expert visually classifies consecutive 30-s epochs of polysomnographic (PSG) data (EEG, EOG and EMG) into wake, rapid eye movement (REM) sleep, and non-REM (NREM) sleep (stages N1-N3). The plot of a sequence of sleep stages is called a hypnogram.

Visual scoring by an expert is time consuming and subjective. Several studies have addressed the interrater reliability and found that correspondence between scorers is less than ideal. The main goal of this project is determine the feasibility of two different wearable technologic devices in differentiating conventional sleep metrics (including wake versus the four different sleep stages) versus those derived from simultaneous gold-standard, in-laboratory PSG methods.

Volunteer participants will undergo an overnight stay in a diagnostic sleep laboratory followed by a next-day maintenance of wakefulness testing (MWT) according to standard AASM protocols. While being monitored by way of multiple, standard surface electrodes on their scalp (EEG monitoring), outer canthus of each eye (EOG monitoring), mentalis (chin) and bilateral anterior tibialis (leg) (EMG monitoring), and torso (electro-cardiogram (EKG) monitoring) during conventional PSG, the NextSense ear-EEG device will be positioned within each external ear canal. In order to increase the homeostatic drive to sleep during MWT the following day (providing greater opportunity to assess biometrics of "sleepiness") the researchers will extend wake four hours past each participant's habitual sleep start time, thereby allowing only 3-4 hours of sleep prior to awakening.

The subsequent day MWT consists of four sessions scheduled at 2-hour intervals during which participants will be asked to remain awake/vigilant, while seated in their room with lights off for 40 minutes. Prior to and following each trial, participants will complete standardized subjective metrics of their sleepiness, and surrogate objective measures of alertness including attention tasks, and the N-back task which is a continuous performance task commonly used to assess working memory and working memory capacity. During the three time intervals separating the four MWT trials, participants will be asked to read and repeat two standard sentences included in the Montreal Cognitive Assessment (MoCA) aloud and the voice audio will be recorded for subsequent analysis. Participants will be asked to wear Ellcie Healthy glasses, concurrent with the NextSense ear-EEG device, during each MWT trial, flanker attention tasks, and text read-aloud tasks.

Eligibility Criteria:
Inclusion Criteria:

* Healthy adults ages 18-60 years of age living within 20 miles of the Emory Sleep Center in Atlanta, Georgia.
* Normal body mass index (BMI) (\>= 18.5 and \<= 28.0 kg/m\^2) at screening visit.
* Has regular sleep-wake habits (e.g., 7-8.5 hours nightly sleep, consistent bed/wake times within 1-2 hours, regular bedtime between 9:30pm-11:30pm, does not oversleep by \> 2 hours on weekends).
* Does not require regular sleep aids or wake promoting medications (including some over the counter cold/allergy medications).

Exclusion Criteria:

* Has a history of diagnosed or suspected sleep disorder (e.g., sleep-related breathing disorders, circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, parasomnias, sleep-related movement disorders, disorders of sleep maintenance or initiation) or other medical condition associated with excessive daytime sleepiness.
* Regular caffeine consumption \> 200 mg per day (1 cup of coffee = 80-120 mg).
* Has a history of major psychiatric disorder (e.g., major depression, bipolar disorder, schizophrenia) or suicidal ideation.
* Current or recent (within the past 6 months) substance dependence (including nicotine, marijuana, alcohol, or any other substance that is likely to affect sleep).
* Has a history of diagnosed or suspected attention deficit/hyperactivity disorder.
* Has performed as a nighttime shift-worker within the past 6 months.
* Inability to safely tolerate wearing earbuds due to recent injury, skin breakdown, or infection.