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Sleep Electroencephalography and Near-Infrared Spectroscopy Measurements for Spaceflight and Analogs

Principal Investigator:
Gary E. Strangman, Ph.D.

Harvard Medical School-Massachusetts General Hospital

Spaceflight is known to reduce sleep duration and negatively affect sleep quality. While actigraphy can be used to identify such sleep changes, the underlying physiology or causes of such disturbances remain to be understood. Brain assessments can be useful in this context for sleep staging, sleep quality assessments, and identification of alterations in cerebral functioning related to sleep disturbance. However, the Earth-standard technologies for brain imaging—CT, MRI, PET, or even typical polysomnography (PSG) systems—are not suitable for spaceflight.

Electroencephalography (EEG) and near-infrared spectroscopy (NIRS) are amenable to packaging in small, lightweight and low- power devices. Importantly, they provide complementary electrophysiological and hemodynamic windows into brain physiology. Dr. Strangman has been developing the NINscan series of devices for mobile (including 24-hour) brain assessment. The most recent such device, NINscan-M, is a multi-use brain imaging system that includes a 64-channel NIRS imaging system and has the potential to support 8-channel ECG/EMG, plus other analog and/or digital sensor inputs.

In this project, Dr. Strangman will enhance his current NINscan-M device to create NINscan-SE: a version specialized for sleep and EEG. NINscan-SE will provide up to 8-channel of flexible EEG/EOG/ECG/EMG alongside the 64-channel NIRS imaging, require minimal training for use, and allow up to 4 additional sensors considered key for sleep research and complementary to those available in spaceflight and the various analog environments. Dr. Strangman will also consolidate a suite of software tools to be used with the potentially large NINscan-SE datasets generated by sleep applications. This suite will facilitate data format conversions, as well as basic research and clinical EEG data analysis on the NINscan-SE datasets. Finally, he will conduct experiments in NASA’s Human Exploration Research Analog (HERA) facility during the 2016 campaign to test NINscan-SE in an operationally-relevant environment.

This effort will provide a device plus software tools that will significantly advance the brain- and sleep-assessment capabilities for spaceflight and Earth-based analogs.

NASA Taskbook Entry

Technical Summary

Our overall objective is to fill the gap in EEG and sleep-research instrumentation for low-resource and/or extreme environments by developing an easy-to-use system capable of up to 8-channel EEG/EOG/EMG/ECG data, with 64-channel NIRS and key sleep-relevant auxiliary sensors, plus appropriate tools for real-time monitoring and post-hoc analysis of such data. To achieve this objective, the following specific aims are proposed:

Specific Aim 1: Adapt NINscan-M to create NINscan-SE (for Sleep & EEG), which will enable selection and deployment of 1-8 EEG analog channels for recording.

Specific Aim 2: Supplement NINscan-SE with other sensors relevant to sleep and/or polysomnography (PSG) research.

We have previously demonstrated our ability to record a single EEG channel using NINscan-M. This capability will be expanded to allow up to 8 channels of such data, selectable by the user. Unused analog channels plus our up-to-4 digital channels will be available for other measurements. ECG is already available; we will develop EMG and EOG as standard PSG options, and potentially respiratory monitoring parameters. We will also enable support for other digital auxiliary sensors and bi-directional synchronization signals.

Specific Aim 3: Develop a software toolkit to help manage and analyze the data collected from NINscan-SE.

We will compile and/or develop and document software tools for: (i) translating the NINscan-SE data files to data formats standard in the domain (e.g., EDF, OpenXDF); (ii) rapidly assessing EEG and NIRS data quality to identify contact issues and signal artifacts, (iii) managing and parsing the large datasets collected from NINscan-SE during night-long recordings, (iv) computing standard clinical sleep measures, as well as (v) tools for time series filtering, computing power spectra, and cross-spectral analysis of the EEG signals.

Specific Aim 4: Conduct human laboratory and analog tests to help characterize and validate NINscan-SE EEG recordings.

We will compare NINscan-SE with commercial EEG and NIRS recordings in human subjects to evaluate system noise and performance. We will also seek to conduct NINscan-SE testing in NASA’s HERA facility. The HERA investigations will provide an operational feasibility test of the system and provide ease-of-use data.

Earth Applications

No current NIRS, EEG or PSG device has both the portability and the multi-use features we propose; thus NINscan-SE could have substantial novel Earth applications. Hospital monitoring applications could include long-duration, non-invasive and multi-modal brain monitoring in the NeuroICU following stroke or traumatic injury. In-office brain function assessment could also be enabled, for assessment of psychiatric states, for monitoring the neural effects of cardiovascular or psychoactive drugs or other therapies, or for brain monitoring during rehabilitation. Mobile monitoring could perhaps have an even larger impact outside the hospital setting. With this wearable monitor, ambulatory multi-parameter monitoring of syncope or epilepsy become possible. If deployed in emergency vehicles, NINscan-SE could potentially be used to detect cerebral or abdominal hemorrhage, ischemia and/or cortical spreading depression by first responders. Home monitoring uses include the particularly large and grown need for home sleep apnea assessments.