Task Brain-Related Assessments for Investigating the Neurophysiology of SANS
Last Published:  07/30/21 01:05:34 PM (Central)
Short Title: BRAIN-SANS
Responsible HRP Element: Human Factors and Behavioral Performance
Collaborating Org(s):
Human Health Countermeasures (HHC) Element
Funding Status: Active - Currently funded and in progress
Procurement Mechanism(s):

Spaceflight Associated Neuro-ocular Syndrome (SANS) remains an important and unmitigated risk to long-duration spaceflight. Current hypotheses suggest that the lack of gravity leads to fluid shifting towards the head, resulting in congestion and/or elevated pressures in the cranial, vascular, and/or lymphatic compartments. NASA is proposing to conduct 30-day head-down tilt (HDT) experiments to test SANS countermeasures at the :envihab facility in Cologne, Germany. We propose to provide numerous key measurements in support of these planned 30-day missions. We will focus in particular on providing a toolkit for detailed neurophysiological and fluid shift assessment and monitoring suitable for measuring both SANS- and countermeasure-related changes. These tools will be designed to complement the standard ocular measures used for SANS diagnosis and monitoring (e.g., optical coherence tomography (OCT), ocular ultrasound (US), fundoscopy, visual acuity). Our proposed measures will include:

    • Intra-ocular pressure (IOP) tonometry, per our team’s prior SANS-relevant work.

    • Relative intracranial pressure (ICP) measurements via distortion product otoacoustic emissions (distortion product     otoacoustic emissions: DPOAE).

    • Blood volume shifts along the body axis via near-infrared spectroscopy (NIRS).

    • Intracranial blood inflow and outflow, via internal jugular vein (IJV) and carotid artery (CA) ultrasound cross-sectional     imaging and Doppler.

    • Cerebral pulsatility assessment, per our parabolic flight and SPACE-COT (Studying Physiological and Anatomical     Cerebral Effects of CO2 and Tilt) :envihab NIRS study.

    • Blood pressure at the level of the head via local, cuff less superficial temporal artery tonometry.

    • Sagittal sinus blood volume imaging and monitoring using diffuse optical tomography (DOT).

    • Cerebral edema assessment based on H2O concentration imaging, similar to that used in our previous altitude sickness     studies.

    • Cerebral electrical activity, via electroencephalogram (EEG) measurements.

    • Dynamic cerebral autoregulation (CAR) assessment during countermeasure (CM) challenges, which can be derived     from the NIRS signals used in the above measurements.

Our tools will be made fully compatible with the planned SANS countermeasures, as well as with those of other teams proposing specific CMs. Along with the measures, we will provide the necessary expertise and analysis to quantify physiological changes associated with SANS countermeasures deployed during the 30-day HDT campaigns at :envihab. Our specific aims are as follows:

    Aim 1: Develop an integrated collection of hardware to support multiple simultaneous, continuous brain monitoring/imaging capabilities, and ensure the hardware and measurements are fully compatible with whatever countermeasures are deployed during the :envihab missions.

    Aim 2: Characterize and quantify individual subjects’ physiological responses to each planned condition, including comparative assessment of SANS countermeasures.

    Aim 3: Relate neurophysiological changes over the 30-day HDT—both with and without SANS-CMs—to cognitive and operational performance, sleep, mood, and ocular measures. Given NASA’s plan to deploy Standard Measures during the study, we expect data will be collected from Cognition, Robotic On-Board Trainer for Research (ROBoT-r), psychological/mood surveys, and the standard ocular measures (OCT, fundoscopy). We will obtain these measures through data sharing so we can investigate the relationship of our neurophysiological measures to each of these outcome assessments. We will focus particular attention on neurophysiological relationships with operational performance ROBoT-r, the development of which was led by Dr. Strangman and which we have deployed in Human Exploration Research Analog (HERA), Neumayer Station in Antarctica, and onboard the International Space Station (ISS).

Jointly, the planned measures and Aims will enable NASA to quantitatively evaluate and compare the (neuro)physiological changes and fluid shifts associated with HDT and SANS countermeasures.