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Ambiguous Tilt and Translation Motion Cues After Space Flight (E136)
Principal Investigator
Research Area:
Species Studied
Scientific Name: Homo sapiens Species: Human

The balance system in the inner ear (otoliths) senses both head translation and head tilt relative to gravity. During space flight, head tilt is not sensed; the brain must therefore learn new ways of orienting oneself in weightlessness, which can then lead to disturbances in perceived motion and balance control upon return to Earth's gravity. The purpose of this research is to examine how the brain adapts to conflicting sensory conditions that may result in motion disturbances after space flight. Before and after space flight, subjects are exposed to a combination of body tilt and translation on a sled or a centrifuge. Changes in eye movements and awareness of position will serve to measure how the brain adapts to conflicting motion cues.

The Ambiguous Tilt and Translation Motion Cues After Space Flight (ZAG) investigation will explore physiological mechanisms and operational implications of spatial disorientation and tilt-translation disturbances reported by crewmembers when making head movements during and following re-entry.

ZAG will also evaluate a tactile prosthesis as a countermeasure for improving control of whole-body orientation during passive tilt and translation motion paradigms.

The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive an accurate representation of spatial orientation. Adaptive changes during space flight in how the brain integrates vestibular cues with other sensory information can lead to impaired movement coordination, vertigo, spatial disorientation and perceptual illusions following G-transitions. This study is designed to examine both the physiological basis and operational implications for disorientation and tilt-translation disturbances following short duration space flights. Specifically, this study addresses three questions:

1) What adaptive changes occur in eye movements and perception in response to different combinations of tilt and translation motion?

2) Do adaptive changes in tilt-translation responses impair ability to manually control vehicle orientation?

3) Can sensory substitution aids (e.g., tactile) mitigate risks associated with manual control of vehicle orientation?

The first specific aim of this experiment will be to examine the effects of stimulus frequency on adaptive changes in eye movements and motion perception during combined tilt and translation motion profiles. Sinusoidal linear motion will be provided by a Variable Radius Centrifuge (VRC) in the roll plane and by a Tilt-Translation Sled (TTS) in the pitch plane. The VRC paradigm provides otolith and other graviceptor cues regarding tilt orientation without concordant canal cues, which are absent during constant velocity rotation. The TTS paradigm, on the other hand, provides canal cues regarding tilt orientation without concordant otolith cues by maintaining the resultant gravitoinertial vector aligned with the body longitudinal (Z) axis. The second specific aim will employ a closed-loop nulling task in which subjects will be tasked to use a joystick to null out tilt motion disturbances on these two devices. The third specific aim will be to evaluate how a tactile prosthesis can be used to improve control performance. The results of this study will contribute to refining the ability of the tactile prosthesis to improve spatial orientation and navigation and serve as a countermeasure for tilt-translation disturbances following space flight.

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Clement G, Wood SJ. Motion perception during tilt and translation after space flight. Acta Astronautica. 2013 November; 92(1): 48-52. []

Motion perception
Vestibular function tests
Physiological adaptation

Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

Centripetal acceleration
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
STS-126 11/14/2008 11/30/2008 16 days
STS-128 08/28/2009 09/11/2009 14 days
STS-129 11/16/2009 11/27/2009 11 days
STS-130 02/08/2010 02/21/2010 14 days
STS-132 05/14/2010 05/26/2010 12 days
STS-133 02/24/2011 03/09/2011 13 days
STS-134 05/16/2011 06/01/2011 16 days

Human Research Program (HRP) Human Research Roadmap (HRR) Information
Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at:

+ Click here for information of how this experiment is contributing to the HRP's path for risk reduction.

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
European Space Agency (ESA)
Alternate Experiment Name