Increased Brain Activation for Dual Tasking with 70-Days Head-Down Bed Rest.

Peng Yuan,Vincent Koppelmans,Jacob J Bloomberg,Rachael D Seidler,Yiri E De Dios,Scott J Wood,Ajitkumar P Mulavara,Igor S Kofman,Nichole E Gadd,Roy Riascos,Patricia A Reuter-Lorenz

doi:10.3389/fnsys.2016.00071

Abstract

Head-down tilt bed rest (HDBR) has been used as a spaceflight analog to simulate the effects of microgravity exposure on human physiology, sensorimotor function, and cognition on Earth. Previous studies have reported that concurrent performance of motor and cognitive tasks can be impaired during space missions. Understanding the consequences of HDBR for neural control of dual tasking may possibly provide insight into neural efficiency during spaceflight. In the current study, we evaluated how dual task performance and the underlying brain activation changed as a function of HDBR. Eighteen healthy men participated in this study. They remained continuously in the 6° head-down tilt position for 70 days. Functional MRI for bimanual finger tapping was acquired during both single task and dual task conditions, and repeated at 7 time points pre-, during- and post-HDBR. Another 12 healthy males participated as controls who did not undergo HDBR. A widely distributed network involving the frontal, parietal, cingulate, temporal, and occipital cortices exhibited increased activation for dual tasking and increased activation differences between dual and single task conditions during HDBR relative to pre- or post-HDBR. This HDBR-related brain activation increase for dual tasking implies that more neurocognitive control is needed for dual task execution during HDBR compared to pre- and post-HDBR. We observed a positive correlation between pre-to-post HDBR changes in dual-task cost of reaction time and pre-to-post HDBR change in dual-task cost of brain activation in several cerebral and cerebellar regions. These findings could be predictive of changes in dual task processing during spaceflight.

Highlights

It has been over half a century since the first man traveled in space
Head-down bed rest (HDBR) has been extensively utilized as an analog to study the effects of cephalic fluid shifts, foot sole unloading, and sensorimotor adaptation that can influence human physiology during exposure to microgravity
In addition to fluid shifts and unloading, both spaceflight and head-down bed rest (HDBR) conditions involve a process of adaptation to a new environment, which is associated with sensory reweighting and potentially neuroplastic changes

Summary

Introduction

It has been over half a century since the first man traveled in space. Since research has revealed a number of physiological and behavioral changes that are associated with spaceflight, such as alterations in muscle, bone, balance, mobility, cardiovascular function, and cognitive performance (Nicogossian et al, 1994; Manzey and Lorenz, 1998; Buckey, 2006; Mulavara et al, 2010; Strangman et al, 2014). Head-down bed rest (HDBR) has been extensively utilized as an analog to study the effects of cephalic fluid shifts, foot sole unloading, and sensorimotor adaptation that can influence human physiology during exposure to microgravity. As a consequence of being in a head-down tilt supine position for a prolonged period, intravascular and extravascular fluids are shifted to the upper body, and head, as is observed in microgravity (Caprihan et al, 1999; Pavy-Le Traon et al, 2007). In addition to fluid shifts and unloading, both spaceflight and HDBR conditions involve a process of adaptation to a new environment, which is associated with sensory reweighting and potentially neuroplastic changes. Most bed rest studies use headdown tilt of −6◦ to mimic cephalic fluid shifts in addition to axial body unloading

Methods

Results

Conclusion