NOTE: Received NCE to 5/31/2010 (from 6/01/2009) per J. Dardano/JSC (12/08)

To develop a model of spatial disorientation (SD) due to microgravity exposure that can be used to familiarize shuttle pilots with SD symptoms during simulated landings, as well as a training tool to improve landing performance after space flight.

This project addresses several questions from the Bioastronautics roadmap concerning disorientation and vertigo during g-level transitions, such as experienced during landing. Development of a ground-based model will help improve shuttle landing performance in the in the short term and will significantly improve mission safety, as several SD incidents impacting Orbiter safety during landing have been documented. In the long term, the SD model developed by this project will have application to future long-duration missions to ensure pilots can monitor automatic landings, and can take manual control of the space craft in off-nominal situations. The SD model may also be used to train astronauts for emergency egress and EVA on a planetary body after g-level transitions.

1) obtain basic data on the characteristics of head and eye movements during simulated orbiter landings,

2) and develop a ground-based analog of the effects of microgravity exposure on pilot performance after spaceflight.

Fulfillment of the project aims was carried out in four phases.

Phase I: Measurement of head and eye movement during vehicle operation

We developed a laptop-based system which simultaneously measures 6 degree-of-freedom (6DOF - triaxial angular rate and triaxial linear acceleration) head movement (using Inertial measurement Units, IMUs), 3D eye movement (yaw, pitch and roll), and 6 DOF motion of a vehicle (or simulator cabin, using an IMU), published as:

MacDougall HG, Moore ST (2005) Functional assessment of head-eye coordination during vehicle operation. Optom Vis Sci 82: 706-715.

Phase II: Head-eye coordination during simulated shuttle landings

We obtained head and eye movement data from six pilots during simulated shuttle landings in an Airbus A340 level-D flight simulator at the Airbus flight training centre in Toulouse, France. In addition, head and eye movements were obtained from a NASA test pilot performing a shuttle landing in the VMS at NASA Ames. Results: during the HAC maneuver (where the shuttle banks around a virtual cylinder to align with the runway) the head and eyes rolled towards the visual horizon with a combined gain of 0.14 of bank angle. Pilots alternated fixation between the instruments and the runway during final approach, almost exclusively focusing on the runway after preflare. Optokinetic nystagmus was observed during rollout. During final approach a Heads-Up Display (HUD) reduced pitch head and eye movement. Conclusions: roll tilt of the head and eyes during the HAC tended to align the retina with the visual horizon. Overlaying critical flight information and the approaching runway with the HUD reduced pitch head and eye movement during orbiter final approach in the VMS relative to the A340 (no HUD installed). Published as:

Moore ST, MacDougall HG, Lesceu X, Speyer JJ, Wuyts F, Clark JB (2008) Head-eye coordination during simulated orbiter landing. Aviat Space Environ Med 79: 888-898.

Phase III: Development of ground-based analog of spatial disorientation after spaceflight In the initial project description we proposed using long-term (60 min) 3 Gx centrifugation (3-g linear acceleration applied along the naso-occipital axis) to replicate the sensorimotor effects of microgravity exposure, as developed by a Dutch group at TNO. Although centrifuged subjects exhibited sensorimotor effects consistent with those observed post-flight the effects were short-lived (<60 min) and often accompanied by motion sickness; 40% of veteran astronauts tested experienced nausea and vomiting following 1-hr of 3-Gx centrifugation (Nooij et al. 2004). The logistical complexity of hyper-g centrifugation and the high incidence of motion sickness limited its value as an analog of post-flight sensorimotor deficits. We therefore developed a novel system utilizing electrical stimulation of the vestibular nerve (Galvanic vestibular stimulation - GVS) to replicate the effects of spaceflight on neurological function. The current waveform used in our GVS analog, a pseudorandom sum of sines, was devised such that sensorimotor performance of normal subjects exposed to acute GVS replicated post-landing data from shuttle and International Space Station (ISS) astronauts, namely postural sway, locomotor impairment and decrements in dynamic visual acuity. Subjective validation was provided by seven veteran astronauts (5 shuttle, 1 ISS, 1 Skylab), who reported that the motor effects and illusory sensations of movement generated by the GVS analog were remarkably similar to their post-landing experience. Published as:

MacDougall H, Moore ST, Curthoys IS, Black FO (2006) Modeling postural instability with Galvanic vestibular stimulation. Exp Brain Res 172: 208-220.

Moore ST, MacDougall H, Peters BT, Bloomberg JJ, Curthoys IS, Cohen H (2006) Modeling locomotor dysfunction following spaceflight with Galvanic vestibular stimulation. Exp Brain Res 174: 647-659.

NSBRI (2006) Galvanic Vestibular Stimulation Countermeasure Demonstrated to Astronauts. In: NSBRI Explorer, July 2006.

Phase IV: Validation of GVS as an analog of post-flight spatial disorientation

The aim of this study was to validate an analog of the sensorimotor effects of microgravity, utilizing pseudorandom bilateral bipolar Galvanic vestibular stimulation (GVS), during shuttle landing simulations. Pilot (N=11) performance was assessed during simulated shuttle landings in the Vertical Motion Simulator at NASA Ames (used for shuttle pilot training). Subjects performed 8 pairs of identical landing profiles (final approach and touchdown) with and without GVS, presented in a pseudorandom order. Target touchdown speed was on target (204 kts) without GVS but increased significantly (P=0.02) during GVS exposure and was at the upper limit (209 kts) of the target range. Unsuccessful (crash) landings increased from 2.3% without GVS to 9% with GVS. Hard landings, with touchdown speed in the 'red' (unacceptable) range (>214 kts), almost doubled from 15.9% without GVS to 30.7% with GVS. GVS was an effective analog of decrements in post-flight shuttle pilot performance. The ability of GVS to replicate a wide range of post-flight sensorimotor deficits (postural, locomotor, oculomotor, fine motor) supports the hypothesis that central changes in processing of low-frequency otolith input underlie space adaptation syndrome. Submitted for publication:

Moore ST, Dilda V, MacDougall HG (2010) Galvanic vestibular stimulation as an analog of spatial disorientation after spaceflight. Exp Brain Res, in review.

Deliverables:

1) We have developed and validated a portable laptop-based system for evaluation of visuo-motor function during complex operational tasks, such as landing the orbiter.

2) We have developed an ambulatory, reversible, ground-based analog (GVS) capable of accurately replicating the sensorimotor (postural, locomotor, oculomotor and fine-motor) effects of spaceflight, suitable for astronaut training.

3) We have validated the GVS analog in an operational setting (VMS shuttle landings).

To develop a model of spatial disorientation (SD) due to microgravity exposure that can be used to familiarize shuttle pilots with SD symptoms during simulated landings, as well as a training tool to improve landing performance after space flight.

This project addresses several questions from the Bioastronautics roadmap concerning disorientation and vertigo during g-level transitions, such as experienced during landing. Development of a ground-based model will help improve shuttle landing performance in the in the short term and will significantly improve mission safety, as several SD incidents impacting Orbiter safety during landing have been documented. In the long term, the SD model developed by this project will have application to future long-duration missions to ensure pilots can monitor automatic landings, and can take manual control of the space craft in off-nominal situations. The SD model may also be used to train astronauts for emergency egress and EVA on a planetary body after g-level transitions.

We have also continued to work on analysis of head-eye coordination during simulated orbiter landings in an Airbus A340 simulator and the Vertical Motion Simulator (VMS) at NASA Ames. In year three we characterized head, eye and aircraft movement during the banking turn prior to final approach, termed the HAC (Heading Alignment Circle) maneuver. The data demonstrated that both the head and eyes tilt into the turn with a combined magnitude of 6º, providing a combined visually-induced head/eye roll-tilt reflex with a gain of around 14% of bank angle, tending. The roll of the head and eyes likely represents a tendency to align the retina with the earth horizon, to improve spatial orientation by establishing the retinal image of the horizon as a primary visuo-spatial cue. In the current year we extended this result to orbiter landings in the VMS, demonstrating that the Heads Up Display (HUD) did not suppress the tilt of the head and eye towards the visual horizon. In addition, we characterized head-eye coordination during final approach in the A340 and VMS. These results have been submitted as a paper to Aviation Space Environmental Medicine, which is currently in review.

To develop a model of spatial disorientation (SD) due to microgravity exposure that can be used to familiarize shuttle pilots with SD symptoms during simulated landings, as well as a training tool to improve landing performance after space flight.

This project addresses several questions from the Bioastronautics roadmap concerning disorientation and vertigo during g-level transitions, such as experienced during landing. Development of a ground-based model will help improve shuttle landing performance in the in the short term and will significantly improve mission safety, as several SD incidents impacting Orbiter safety during landing have been documented. In the long term, the SD model developed by this project will have application to future long-duration missions to ensure pilots can monitor automatic landings, and can take manual control of the space craft in off-nominal situations. The SD model may also be used to train astronauts for emergency egress and EVA on a planetary body after g-level transitions.

We have also continued to work on analysis of head-eye coordination during simulated Orbiter landings. Head, eye and aircraft movement during the banking turn prior to final approach, termed the HAC (Heading Alignment Circle) maneuver, were obtained in 5 pilot subjects in an Airbus A340 full-motion simulator. The data shows that both the head and eyes tilt into the turn with a combined magnitude of 6º, tending to align the retina with the visual horizon. This response was not apparent in zero visibility, and is likely produced from the tilted image of the horizon on the retina. Previous studies (Gallimore et al. 1999, 2000; Patterson et al. 1997) have shown that pilots tilt their head into the turn during banking (the optokinetic cervical reflex); our results extend this finding by demonstrating that the eyes also tilt into the turn, providing a combined visually-induced head/eye roll-tilt reflex with a gain of around 14% of bank angle.

In a related project we have modified the hardware used in the current project to measure stride length in patients with Parkinson’s Disease (PD). A recent publication (Moore et al 2006) demonstrated that long-term community monitoring of gait in PD patients provided an objective measure of stride length changes due to levodopa-related medications and disease severity.

Preliminary data was obtained in September 2005 from one subject undergoing GVS during simulated Orbiter landings in the Vertical Motion Simulator (VMS) at NASA Ames Research Center. The pilot reported that GVS added significantly to the workload required to land the shuttle in a manner similar to “fighting” through vertigo during an instrument approach. In addition, the subject noted that “I had really had a physical and mental workout by the time I got the shuttle on the ground – this is much more likely to be what the astronauts have to contend with”. In the next phase of testing we aim to use GVS in the VMS to test the hypothesis that GVS generates spatial disorientation similar to that experienced after spaceflight, and will induce degradation in pilot performance analogous to that observed in actual shuttle landings.

We examined whether g-transitions alone could account for decrements in pilot performance in an experiment flown aboard two ESA parabolic flight campaigns. Subjects were asked to identify targets that appeared at random on a large screen and head and eye movements were simultaneously acquired. Preliminary data suggests that performance was consistent across the g-transitions (1-g to 1.8-g to 0-g to 1.8-g to 1-g). This supports the original hypothesis of this project; that degradation of pilot performance is due to extended microgravity exposure during space flight, rather than the g-level transitions of reentry.

We have applied elements of the measurement technology developed during this project to measure head movement during unrestrained daily activity over 10 hours in normal subjects (N=20). The results were striking: during locomotor activities (walking, cycling etc) subjects adopted a cadence of 2 Hz (SD 0.15) that was independent of age, height, gender or body mass index. This basic result is of considerable significance – there exists a spontaneous 2 Hz tempo of human locomotion. This work has been published (Macdougall and Moore 2005) and is included as an Appendix to this report.

Ambulatory system for delivering Galvanic Vestibular Stimulation to simulate postural, perceptual and oculomotor effects of microgravity-induced spatial disorientation has been developed.

Head-eye coordination during simulated shuttle landings has been assessed in 6 subjects in a commercial flight simulator (Airbus, Toulouse, France).

GVS as a model for SD has been verified using tests of postural stability, performance on an obstacle course, and dynamic visual acuity. (These tests are routinely performed on returning astronauts). The data demonstrate that our GVS paradigm generates deficits in these areas very similiar to that observed in astronauts after flight.

To develop a model of spatial disorientation (SD) due to microgravity exposure that can be used to familiarize shuttle pilots with SD symptoms during simulated landings, as well as a training tool to improve landing performance after space flight.

This project addresses several questions from the Bioastronautics roadmap concerning disorientation and vertigo during g-level transitions, such as experienced during landing. Development of a ground-based model will help improve shuttle landing performance in the in the short term and will significantly improve mission safety, as several SD incidents impacting Orbiter safety during landing have been documented. In the long term, the SD model developed by this project will have application to future long-duration missions to ensure pilots can monitor automatic landings, and can take manual control of the space craft in off-nominal situations. The SD model may also be used to train astronauts for emergency egress and EVA on a planetary body after g-level transitions.

[Ed. note: FY2004 record added to Task Book in 02/2010 for statistical purposes]