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Human Research Program

Objective Detection, Evaluation and Countermeasures for In-flight Depression

Completed Technology Project

Project Introduction

In the past year, we made significant progress in three primary areas: experimental, computational, and technology development. On the experimental front we completed our neuroimaging study of depression. The goal was to identify more objective brain biomarkers for detecting depression and for assessing depression severity. We recruited 20 depressed individuals (age 30-60, Bachelor's degree or higher, un-medicated) along with 19 matched healthy controls and collected data on multiple structural and functional MRI (magnetic resonance imaging) and NIN measures. Measures were examined for (1) their ability to detect depression (Aim 1a), and (2) their ability to assess depression severity (Aim 1b). We identified multiple putative brain biomarkers for both detection and assessment, including both structural and functional brain measures. Manuscripts are in preparation. We also completed data analysis for two analog tests. In our head-down tilt (HDT) study, headward fluid shifts were hypothesized to adversely affect NIN sensitivity while performing our depression study's working memory tasks. Modest sensitivity loss was observed during acute -6 degree HDT relative to +45 degree head up tilt, but similar functional activation was still detected by NIN. This demonstrated the sensitivity of NIN to brain function in these tasks (Aim 3), as well as the robustness of NIN to HDT. In our Aug 2010 Kilimanjaro analog study, we examined data from 6 hikers at 6 different altitudes performing Valsalva and Mueller maneuvers. We observed significant increases in cerebral blood volume (CBV) with altitude, but significant decreases in CBV in individuals affected by acute mountain sickness. This demonstrated (1) the ability to perform NIN experiments monitoring cerebral physiology in an extreme environment, (2) the sensitivity of NINscan 2a to cerebral hemodynamics (Aim 3), and (3) provided preliminary evidence that cerebral edema and mild increases in intracranial pressure are involved in acute mountain sickness. On the computational front, we completed analysis of our simulations modeling the distribution of photons migrating through the head. This generated the most detailed maps to date of NIN sensitivity to brain tissue and also supports Aim 3. Sensitivity was found to be more spatially variable than previously assumed, but we identified ways to design probes and devices to compensate for such sensitivity differences. Two manuscripts describing the results of this work are currently under review. On the technology development front, we completed NINscan 3a, a next-generation device that is considerably more sensitive and capable than NINscan 2a. We also completed NINscan TD, a microcontroller-based design that provides even more flexibility (including light and detector gain controls) as well as a proof of concept design for scaling to whole-head neuroimaging. These efforts strongly support the goal of developing technologies suitable for brain imaging in spaceflight (Aim 2). More »

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Project Duration

This is a historic project that was completed before the creation of TechPort on October 1, 2012. Available data has been included. This record may contain less data than currently active projects.