Task Progress:
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Study Schedule: Repeated measures were conducted on 12 Shuttle crewmembers for ZAG and 10 Shuttle crewmembers for Otolith. Measurements were obtained for each experiment pre-flight at L-120 (±30), L-90 (±30), and L-30 (±10) days and post-flight at R+0, R+1 (TTS only), R+2 or 3, R+4 or 5, and R+8-10 days. The specific Shuttle missions included: STS-123 (1 ZAG only), STS-126 (3 each), STS-128 (1 each), STS-129 (1 each), STS-130 (2 ZAG and 1 Otolith), STS-132 (2 each), STS-133 (1 each), and STS-134 (1 each). An integrated protocol on the variable radius centrifuge was implemented for subjects participating in both experiments. Ground control measures on most measures were also obtained on 8 normative subjects.
ZAG Variable Radius Centrifugation: Constant velocity variable radius centrifugation (VRC) was utilized to elicit otolith reflexes in the lateral plane without concordant roll canal cues. Subjects were restrained on a chair that was mounted on a small translation stage fixed to a rotator. Subjects donned an elastic belt with vibrotactile stimulators used to provide orientation cues when the chair position exceeded pre-set threshold levels. Subjects wore a lightweight mask with video cameras and near-infrared illumination to allow eye movement recording in darkness. A joystick mounted directly in front of the subject was used for both motion perception and manual control tasks (nulling chair translation). This session was initiated with a slow acceleration (3°/s2) to a constant velocity of 216°/s, typically after the Otolith VRC was performed. Subjects continued to rotate for 60 s to allow the initial per-rotatory response to decay. After the subjects no longer sensed the rotation, the chair was offset at various positions to obtain verbal reports of tilt perception with chair positions corresponding to ±5°, ±10° and ±15°. Subjects then used the joystick to control the chair orientation. Two closed-loop nulling runs were performed (with and without vibrotactile feedback) in which subjects attempted to maintain the chair centered over the axis of rotation (no tilt) during the same random step protocol. The maximum chair translation was limited to ±20 cm. The primary dependent measures for the manual control runs was the root mean square (RMS) position error, and the amount of the disturbance that was effectively corrected referred to below as “nulling gain.” During the final part of this session, subjects oscillated along the track at three discrete frequencies (0.15, 0.3, and 0.6 Hz). The amplitude of the chair translation at each frequency was adjusted so that the tilt stimuli (resultant of translation and centripetal accelerations) was ±10°. Subjects reported their perception of roll tilt and lateral translation at each frequency using the joystick and verbal reports. The primary dependent measures for the sinusoidal data are the amplitude and phase of both eye movements and motion perception.
We hypothesized that adaptation of otolith-mediated responses will be greatest in the mid-frequency range where there is a crossover of tilt-translation responses. Motion perception was obtained using both static and dynamic roll tilt stimuli. All subjects tested on landing day (7 of 12) reported an increased sense of static roll tilt. This increase in tilt perception recovered by the time testing resumed at Johnson Space Center (JSC) 2-3 days after landing. During the sinusoidal VRC oscillations, all subjects reported an increased sense of translation at higher frequencies. This difference between translation and tilt perception was even greater on landing day. Quadric fits through the average responses at each frequency suggest that the cross-over frequency shifted from ~0.25 Hz preflight to ~0.12 Hz on landing day. As with the static tilt perception, these adaptive changes in dynamic translation perception tended to recover by the time testing resumed at JSC 2-3 days after landing.There were clear deficits in some crewmembers' ability to null out tilt disturbances during VRC on landing day. On landing day the manual control performance without vibrotactile feedback was reduced by >30% based on the gain or the amount of tilt disturbance successfully nulled. A similar effect is observed for RMS position and velocity error. Manual control performance tended to return to baseline levels within 1-2 days following landing. Nulling gain was significantly improved with vibrotactile feedback. It is important to note that the landing day performance with tactors was as good as preflight performance without tactors.
ZAG Tilt-Translation Sled: This session flow was similar to the ZAG VRC, except that the linear acceleration stimuli are directed along the pitch plane using the Tilt-Translation Sled (TTS) that provides various combinations of tilt and translation stimuli. Subjects were restrained on a tilt chair that was mounted inside a light-tight enclosure. The tilt motion was provided by dual-wheel friction wheels using direct drive servo motors and a pivoting yoke assembly to provide up to ±20° dynamic displacement. The translation motion along the air bearing track was generated by three linear motors operated in series in a single magnet track. During this session, subjects were oriented so that translation was along the fore-aft direction while tilts were in the sagittal plane. The vibrotactile stimulators were located on the back and front of the torso to provide orientation cues of pitch tilt. Subjects were restrained in the chair with straps and padding around the shoulders and waist. The chair height was adjusted so that the head (interaural axis) was aligned with the tilt axis, and the head was maintained in an upright orientation. Noise cancelling headphones were used to mask auditory cues. As with the VRC, a chair-mounted joystick was used for both motion perception and manual control tasks (nulling chair tilt). The session started with subjects providing verbal reports of perception during a random step profile with tilts at ±2.5°, ±5°, and ±7.5°. Subjects then used the joystick to control the chair tilt orientation during the same random step protocol. This closed-loop nulling run was performed with and without vibrotactile feedback. During the next part of this session, subjects either translated along the track or tilted at ±10° in the pitch plane at three discrete frequencies (0.15, 0.3, and 0.6 Hz). The amplitude of the translation at each frequency was adjusted so that the acceleration was ±1.73 m/s2, equivalent to ±10°. Subjects reported their perception of pitch tilt and fore-aft translation at each frequency using the joystick to indicate phase and verbal reports to indicate amplitude. The final two runs utilized concomitant tilt and translation motion phased such that resultant gravitoinertial vector remained aligned with the body longitudinal Z axis, thus it was referred to as Z-axis gravitoinertial stimulus paradigm, or ZAG. During these runs, which utilized a sum-of-sinusoids between 0.01 and 0.6 Hz, subjects were asked to maintain their tilt orientation Earth vertical, thus nulling out any tilt disturbance. The runs were performed with and without the vibrotactile feedback. The primary dependent measures for the TTS ZAG session are similar to the VRC session.
The first opportunity for these tests were on R+1 following the crew return ceremony. As with the VRC, motion perception was obtained using both static and dynamic tilt stimuli. There were no significant changes in the static pitch tilt runs. As described above, the increase in VRC static roll tilt perception was only observed on landing day. Therefore, the lack of a difference between preflight and postflight static pitch tilt may be due to the delay in testing. Since the pitch tilts were accomplished using rotation about an Earth-horizontal axis, these differences may also be attributed to the fact that the tilts were signaled by both otolith and canal cues on the TTS. While there may be axis specific differences between pitch and roll, the roll tilts on the VRC involved otolith cues only. Another difference was the range of tilts between the VRC (±15°) and the TTS (±7.5°). While changes in static perception were stronger in roll on the VRC versus in pitch on the TTS, there was an opposite effect for the dynamic runs. As with the VRC, all subjects reported an increased sense of translation at higher frequencies. However, this difference between translation and tilt perception was not only greater on R+1, but persisted longer post-flight. Quadric fits through the average responses at each frequency suggest that the cross-over frequency shift persisted until the last postflight test sessions. This is in contrast to the VRC crossover shifts which tended to recover by the second test 2-3 days after landing. Preflight the nulling gain and RMS position error were similar for the TTS static pitch tilt runs as for the VRC static roll tilt runs. However, in contrast to the landing day VRC manual control runs, there were no deficits in manual control performance during the TTS static pitch runs by R+1. Taken together, these data suggest that the decrements in nulling static disturbances in tilt orientation following short-duration flight are recovered by R+1. As during the VRC, the vibrotactile feedback improved manual closed-loop nulling performance across all sessions except the initial familiarization session. The overall manual control performance during the ZAG profiles on the TTS was poor compared to the static tilt profiles. This was expected since the tilt and translation motion were synchronized to minimize the sense of tilt, and since these profiles include frequency components beyond the ability to nulling out tilt disturbances (see for example, Merfeld 1996). While the performance was improved with vibrotactile feedback, the overall nulling gain remained significantly below the static nulling trials.
Otolith Variable Radius Centrifugation: The VRC session for Otolith was initiated with a slow acceleration (3°/s2) to a constant velocity of 400°/s, typically before the ZAG VRC session was performed (see above). Subjects continued to rotate for ~2 min to allow the initial per-rotary response to decay. After the subjects no longer sensed the rotation, the otolith-mediated perception and eye movement responses were obtained with the chair centered, and then offset to either left or right eccentric positions. The displacement (±3.5 cm) was designed to place one ear over the axis of rotation with the other one offset, thus evoking unilateral otolith (utricular) responses from the linear (centripetal) acceleration to the offset ear. The Subjective Visual Vertical (SVV) was measured by having subjects use the hand-controller to align a luminous line along the perceived gravitational vertical, thus providing an estimate of tilt perception. The otolith-ocular reflex (OOR) was then measured for up to 10 cycles using the eye tracker while the chair position continued to alternate between center and left/right eccentric positions. The primary dependent measures consisted of SVV tilt perception amplitude and asymmetry, and the ocular torsion amplitude and asymmetry.
When subjects on the VRC were positioned and maintained at an eccentricity of ± 3.5 cm to their right or to their left during eccentric centrifugation at 400 deg/s, they experienced the typical somatosensory illusion of being statically tilted in roll. In addition to the SVV measures, this perception was assessed by verbal reports of the amplitude of perceived tilt. Before the flight, this amplitude of perceived tilt was close to that of the tilt of the GIF relative to gravity, i.e., 10 deg. After the flight there was a clear increase in the perceived tilt angle in roll (+25% relative to pre-flight). Note this increase in roll tilt perception on landing day is consistent with the ZAG static tilt perception runs performed at lower centrifuge velocity.The distribution of the preflight SVV asymmetry ratios were within normal limits. Postflight changes in asymmetry ratios were normalized so that a positive change represented in increase in asymmetry in the same direction as demonstrated preflight, while a negative change represented a reversal in asymmetry. Changes in the SVV asymmetry ratios increased in the same direction for the 6 of 10 subjects tested on landing day. All subjects showed a reversal in asymmetry during subsequent postflight testing with a return to baseline levels within the first week postflight. The distribution of the preflight OOR asymmetry ratios were also within normal limits. While the changes in OOR asymmetry values were not as striking postflight, they did follow a similar pattern with a reversal in asymmetry during the R+2/3 tests and subsequent return to preflight levels within the first week following the short-duration flights.
Otolith Vestibular Evoked Myogenic Potential: The Vestibular Evoked Myogenic Potential (VEMP) measured otolith saccular function indirectly through a vestibulo-collic reflex. The saccule is just under the middle ear stapes footplate, and is sensitive to acoustical stimulation. Brief (0.1 ms) auditory clicks gave rise to a short-latency inhibition of activity in the contracted neck (sternocleidomastoid) muscle. Muscle activity in the neck was recorded with surface electrodes as subjects were supine and lifted their heads to contract the sternocleidomastoid muscle. Auditory stimuli were presented monaurally to the same side as the measured neck muscle (e.g., measured from the right side of the neck during auditory stimuli to the right ear). The auditory stimuli were presented through headphones. Responses were averaged across sets of 150 auditory clicks (5 clicks per second) presented at levels from 120 to 140 dB SPL (sound pressure level) during tonic contraction. The primary dependent measure consisted of the peak-to-peak amplitude from the positive peak occurring at ~13 msec following each click to the negative peak occurring ~10 msec later.
The distribution of the preflight VEMP asymmetry ratios were also within normal limits. In contrast to the utricular measures, the the changes in saccular VEMP asymmetry values were in the opposite direction postflight. The changes were not significantly different by the R+2/3 test sessions.
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Abstracts for Journals and Proceedings
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Clarke AH, Schönfeld U, Wood SJ. "Modification of otolith reflex asymmetries following space flight." 35th MidWinter Meeting of the Association for Research in Otolaryngology, San Diego, CA, February 25-29, 2012. Association for Research in Otolaryngology Abstracts. 2012;35:23. Abstract 63. , Feb-2012
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Abstracts for Journals and Proceedings
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Clément GR, Wood SJ. "Motion perception during tilt and translation after spaceflight." 18th IAA Humans in Space Symposium, Houston, TX, April 11-15, 2011. 18th IAA Humans in Space Symposium, Houston, TX, April 11-15, 2011. , Apr-2011
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Abstracts for Journals and Proceedings
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Danielson RW, Wood SJ. "Auditory and vestibular issues related to human spaceflight." Audiology NOW! 22nd Annual Convention of the American Academy of Audiology, San Diego, CA, April 14-17, 2010. Audiology NOW! 22nd Annual Convention of the American Academy of Audiology, San Diego, CA, April 14-17, 2010. , Apr-2010
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Abstracts for Journals and Proceedings
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Holly JE, Zhang G, Wood SJ. "Gravito-inertial force resolution in perception of synchronized tilt and translation." 41st Annual Society for Neuroscience Meeting, Washington D.C., November 12-16, 2011. 41st Annual Society for Neuroscience Meeting, Washington D.C., November 12-16, 2011. Program#/Poster#: 580.13/FF34. Abstract available at http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=079425ca-7e0f-440f-9ac1-e7a3f918c2d9&cKey=bf015e89-70e8-4771-a542-a5c128f16708&mKey=%7b8334BE29-8911-4991-8C31-32B32DD5E6C8%7d ; accessed 5/2/2012. , Nov-2011
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Abstracts for Journals and Proceedings
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Wood SJ, Rupert AH, Vanya RD, Esteves JT, Clément GR. "Influence of vibrotactile feedback on controlling tilt motion after spaceflight." 18th IAA Humans in Space Symposium, Houston, TX, April 11-15, 2011. 18th IAA Humans in Space Symposium, Houston, TX, April 11-15, 2011. , Apr-2011
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Abstracts for Journals and Proceedings
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Wood SJ, Vanya RD, Esteves JT, Rupert AH, Clément GR. "Modification of motion perception and manual control following short-duration spaceflight." 2012 NASA Human Research Program Investigators’ Workshop, Houston, TX, February 14-16, 2012. 2012 NASA Human Research Program Investigators’ Workshop, Houston, TX, February 14-16, 2012. , Feb-2012
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Articles in Peer-reviewed Journals
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Clément G, Harm DL, Rupert AH, Beaton KH, Wood SJ. "Ambiguous tilt and translation motion cues in astronauts after space flight (ZAG)." J Gravit Physiol 2008;15(1):P13-4. , Jan-2008
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Articles in Peer-reviewed Journals
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Paloski WH, Oman CM, Bloomberg JJ, Reschke MF, Wood SJ, Harm DL, Peters BT, Mulavara AP, Locke JP, Stone LS. "Risk of sensory-motor performance failures during exploration-class space missions: A review of the evidence and recommendations for future research." J Gravit Physiol 2008;15(2):1-29. , Aug-2008
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Articles in Peer-reviewed Journals
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Clément G, Wood SJ. "Motion perception during tilt and translation after space flight." Acta Astronautica. 2013 Nov;92(1):48-52. (Originally reported in May 2012 as 'In Press, Corrected Proof, Available online 4 April 2012.') http://dx.doi.org/10.1016/j.actaastro.2012.03.011
, Nov-2013
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Articles in Peer-reviewed Journals
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Clément G, Wood SJ. "Eye movements and motion perception during off-vertical axis rotation after spaceflight." Journal of Vestibular Research. 2013;23(1):13-22. (Originally reported in May 2012 as 'Submitted as of May 2012.') http://dx.doi.org/10.3233/VES-130471 ; PubMed PMID: 23549051
, Jan-2013
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Articles in Peer-reviewed Journals
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Reschke MF, Wood SJ, Cerisano JK, Harm DL, Bloomberg JJ, Paloski WH, Schlegel TT, Clément G. "Contributions of the space shuttle program to spaceflight related sensorimotor research." Journal of Gravitational Physiology. Submitted, as of May 2012. , May-2012
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Articles in Peer-reviewed Journals
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Clément G, Wood SJ. "Rocking or rolling--perception of ambiguous motion after returning from space." PLoS One. 2014 Oct 29;9(10):e111107. e Collection 2014. http://dx.doi.org/10.1371/journal.pone.0111107 ; PubMed PMID: 25354042; PubMed Central PMCID: PMC4213005 , Oct-2014
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Books/Book Chapters
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Clément G, Wood SJ. "Space physiology." in "Primer on the Autonomic Nervous System. 3rd edition." Ed. D. Robertson, editor in chief; I. Biaggioni et al. Amsterdam ; Boston : Elsevier/AP, 2012. p. 283-286., Jan-2012
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Books/Book Chapters
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Harm DL, Reschke M, Wood SJ.
"Spatial orientation and motion perception in microgravity." in "Cambridge Handbook of Applied Perception Research. Cambridge Handbooks in Psychology." Ed. R.R. Hoffman et al. New York : Cambridge University Press, 2015. p. 912-929. , Jan-2015
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