NOTE: End date changed to 2/13/2021 per L. Taylor/JSC (Ed., 7/29/2020)

NOTE: End date changed to 9/30/2020 per L. Taylor/JSC (Ed., 8/23/18)

The subjective straight-ahead direction is a very basic perceptual reference for spatial orientation, movement, and locomotion. The perceived straight-ahead along the horizontal and vertical meridian is largely determined by both otolith and somatosensory inputs. Otolith and somatosensory inputs are altered in microgravity and will change this reference point. Adaptive processes are taking place within the central nervous system to take into account the new environment and compute new spatial egocentric and world-centered representations or frames of reference. This project will measure and monitor how these frames change over time by investigating eye movements and perceptual reports.

The three specific aims include:

Specific Aim 1: Near & Far Fixation. The first aim is to examine binocular eye movements when subjects fixate on actual targets (normal vision) and then imagine these same targets (occluded vision) in the straight-ahead direction relative to their heading. Initially, the subjects’ gaze direction and fixation distance will be recorded as they explore the space around them using eye movements in darkness. Next, they will be asked to fixate on straight ahead head-fixed targets located at a near distance (arm’s length, ~0.5 m) and far distance (beyond 2 m). Responses will be compared with different tilt orientations, including pitch tilt forward and backward up to 15 deg. During separate trials, subjects will attempt to maintain fixation on a far Earth-fixed target with and without a vibrotactile sensory aid that indicates how far one has tilted relative to the straight ahead direction.

Specific Aim 2: Eye and Arm Movements. The second aim is to examine directed horizontal and vertical eye and arm movements, relative to Earth coordinates and relative to the subject’s head/body reference. This task will be performed with the subject upright and then tilted in roll directions up to 30 deg. The trajectory of the directed eye and arm movements made in darkness are expected to reflect perceptual tilt errors.

Specific Aim 3: Near and Far VOR. The third aim is to examine the influence of target distance on the vestibulo-ocular reflex (VOR) during vertical translation movements. Subjects will stare at actual visual targets (normal vision) at various distances (near and far) in the straight-ahead direction while passively translated up and down using a spring-loaded chair. Vision will then be occluded, and the VOR will be recorded as the subject continues to fixate on the same target locations during translation. In addition to these periodic oscillations (~2.0 Hz), eye movements will also be recorded with vision during unpredictable passive head thrusts up and down using the spring-loaded chair.

For each of our specific aims above, our general hypothesis is that responses will be influenced by how accurately subjects perceive their spatial orientation. We will test this hypothesis by comparing responses with and without visual feedback. We also hypothesize for Specific Aim 1 that a vibrotactile sensory aid of tilt position will improve spatial orientation and this reduces gaze fixation errors.

Study Participants: Eight International Space Station (ISS) crewmembers were recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+1 day, R+4 (±2) days, and R+8 (±2) days. Sixteen ground-based subjects were recruited to participate in a ground control study for up to 3 sessions. This study was implemented by the European Space Agency and is not carried in the U.S. ISS utilization plans.

Risk Characterization, Quantification\Evidence: This task will contribute to gap closure by providing information regarding any changes in an individual's egocentric reference that might have negative consequences on evaluating the direction of an approaching object or on the accuracy of reaching movements. This information is important for understanding the problems associated with the long-term effects of microgravity on astronauts and how they re-adapt to the return of gravitational forces on Earth or other planetary surfaces.

Countermeasure\Prototype Hardware or Software: This task will contribute to gap closure by evaluating how vibrotactile feedback of reference frames can be used to improve spatial orientation of fixation on space-fixed targets.

Specific Aim 1

The amplitude of perceived tilt during passive tilt in roll (± 25º) significantly increased on R+1 compared to preflight. However, the amplitude of perceived tilt during passive tilt in pitch (± 15º) did not change significantly on R+1 compared to preflight. The perceived amplitude of translation tended to increase during roll tilt and during pitch tilt after spaceflight. The perception of distances of visual targets ranging from 0.5 m to ~2 m was affected by target distance, with greater errors with near targets =1 m. However, the distance of a visual target was not affected by spaceflight within the timeframe of our tests. The eye movement data indicate that the amplitude of ocular counter-rolling during tilt in roll was reduced for several days after return from long-duration spaceflight. This decrease in amplitude was not accompanied by changes in the asymmetry of OCR between right and left head tilt (Reschke et al. 2018).

Specific Aim 2

When subjects imagined a laboratory-fixed target while being tilted in pitch at angles varying from 15º backward to 15º forward, the vertical eye position shifted downward ~5º compared to when they were actually looking at the target, thus indicating a downward shift of the subjective straight-ahead. The addition of a vibrotactile feedback of tilt when the subjects imagined the targets partially compensated for this downward shift of the subjective straight-ahead. This result confirms that a vibrotactile feedback is a useful countermeasure after landing for mitigating the effects of spaceflight on spatial disorientation and manual control (Clément et al. 2018; Reschke & Clément 2018).

Specific Aim 3

The translational vestibulo-ocular reflex (tVOR) measurements during vertical oscillations were analyzed using a method that has been recently published (Clément et al. 2019). The tVOR at high frequency is an important otolith-mediated response to stabilize gaze during natural locomotion. The tVOR was significantly increased with near viewing of actual targets. This effect was less pronounced with subjects imagining these targets in darkness. A decrease in the tVOR gain was observed in some subjects, which could potentially alter gaze fixation during locomotion. Therefore, the results of this study confirm the potential contribution of a spaceflight-adapted vestibular system in locomotion impairment after spaceflight.

CONCLUSIONS

The results of this study indicate that after spaceflight, there is an over-estimation of perceived roll tilt, but that there is no change in perceived pitch tilt. Also, the perceived amplitude of translation tends to increase during roll and pitch tilt after spaceflight.

Ocular counter-rolling during roll tilt decreases after long-duration spaceflight.

The subjective straight-ahead shifts downward after spaceflight (~ 5º). A vibrotactile feedback of tilt partially compensates for this downward shift in some subjects.

One primary limitation of this study is the delayed testing due to the time required for direct return to JSC. Recent field tests (Reschke et al. 2020) suggest that any impairments observed following +24 hrs underestimate the initial decrement soon after landing.

The observed changes in egocentric reference might impair an individual’s ability to evaluate the direction of an approaching object or the accuracy of their reaching movements or locomotion. The use of vibrotactile sensory aid partially compensates to correct the representation of the body tilted relative to gravity and could partially help in mitigating risks caused by this loss of spatial orientation.

References

Reschke MF, Wood SJ, Clément G (2018) Ocular counter rolling in astronauts after short-and long-duration spaceflight. Scientific Reports 8: 7747.

Clément G, Wood SJ, Paloski WE, Reschke MF (2019) Changes in gain of horizontal vestibulo-ocular reflex during spaceflight: Journal of Vestibular Research 29: 241-251.

Clément G, Reschke MF, Wood SJ (2018) Vibrotactile feedback improves manual control of tilt after spaceflight. Frontiers in Physiology 9: 1850.

Reschke MF, Clément G (2018) Vestibular and sensorimotor dysfunction during spaceflight. Current Pathobiology Reports6 (3): 177-183.

Reschke MF, Kozlovskaya IB, Lysova N, Kitov V, Rukavishnikov I, Kofman IS, Tomilovskaya ES, Rosenberg MJ, Osetsky N, Fomina E, Grishin A, Wood SJ. (2020) [Joint Russian-USA field test: Implications for deconditioned crew following long duration spaceflight]. Aviakosm Ekolog Med. 2020;54(6):94-100.

NOTE: End date changed to 2/13/2021 per L. Taylor/JSC (Ed., 7/29/2020)

NOTE: End date changed to 9/30/2020 per L. Taylor/JSC (Ed., 8/23/18)

The subjective straight-ahead direction is a very basic perceptual reference for spatial orientation, movement, and locomotion. The perceived straight-ahead along the horizontal and vertical meridian is largely determined by both otolith and somatosensory inputs. Otolith and somatosensory inputs are altered in microgravity and will change this reference point. Adaptive processes are taking place within the central nervous system to take into account the new environment and compute new spatial egocentric and world-centered representations or frames of reference. This project will measure and monitor how these frames change over time by investigating eye movements and perceptual reports.

The three specific aims include:

Specific Aim 1: Near & Far Fixation. The first aim is to examine binocular eye movements when subjects fixate on actual targets (normal vision) and then imagine these same targets (occluded vision) in the straight-ahead direction relative to their heading. Initially, the subjects’ gaze direction and fixation distance will be recorded as they explore the space around them using eye movements in darkness. Next, they will be asked to fixate on straight ahead head-fixed targets located at a near distance (arm’s length, ~0.5 m) and far distance (beyond 2 m). Responses will be compared with different tilt orientations, including pitch tilt forward and backward up to 15 deg. During separate trials, subjects will attempt to maintain fixation on a far Earth-fixed target with and without a vibrotactile sensory aid that indicates how far one has tilted relative to the straight ahead direction.

Specific Aim 2: Eye and Arm Movements. The second aim is to examine directed horizontal and vertical eye and arm movements, relative to Earth coordinates and relative to the subject’s head/body reference. This task will be performed with the subject upright and then tilted in roll directions up to 30 deg. The trajectory of the directed eye and arm movements made in darkness are expected to reflect perceptual tilt errors.

Specific Aim 3: Near and Far VOR. The third aim is to examine the influence of target distance on the vestibulo-ocular reflex (VOR) during vertical translation movements. Subjects will stare at actual visual targets (normal vision) at various distances (near and far) in the straight-ahead direction while passively translated up and down using a spring-loaded chair. Vision will then be occluded, and the VOR will be recorded as the subject continues to fixate on the same target locations during translation. In addition to these periodic oscillations (~2.0 Hz), eye movements will also be recorded with vision during unpredictable passive head thrusts up and down using the spring-loaded chair.

For each of our specific aims above, our general hypothesis is that responses will be influenced by how accurately subjects perceive their spatial orientation. We will test this hypothesis by comparing responses with and without visual feedback. We also hypothesize for Specific Aim 1 that a vibrotactile sensory aid of tilt position will improve spatial orientation and this reduces gaze fixation errors.

Study Participants: Eight International Space Station (ISS) crewmembers will be recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+0/1 day, R+4 (±2) days, and R+8 (±2) days. Sixteen ground-based subjects will be recruited to participate in a ground control study for up to 3 sessions. A limited number of subjects will also participate in parabolic flight study as resources permit. This study is being implemented by the European Space Agency and is not carried in the U.S. ISS utilization plans.

Risk Characterization, Quantification\Evidence: This task will contribute to gap closure by providing information regarding any changes in an individual's egocentric reference that might have negative consequences on evaluating the direction of an approaching object or on the accuracy of reaching movements. This information is important for understanding the problems associated with the long-term effects of microgravity on astronauts and how they re-adapt to the return of gravitational forces on Earth or other planetary surfaces.

Countermeasure\Prototype Hardware or Software: This task will contribute to gap closure by evaluating how vibrotactile feedback of reference frames can be used to improve spatial orientation of fixation on space-fixed targets.

Eight International Space Station (ISS) crewmembers were recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+0/1 day, R+4 (± 2) days, and R+8 (± 2) days. An informed consent briefing was delivered to 26 ISS crewmembers between March 2014 and May 2018. The last crewmember has been recruited on May 2018 after which the enrollment was closed. Preflight data was initiated in 2015 following approval for this study to be implemented for pre- and post-flight testing only. One subject was withdrawn from the study due to changes in post-flight test plans. Eight ISS crewmember have completed pre- and post-flight data collection.

Preliminary analysis of the perception data on 6 subjects indicates that the amplitude of perceived tilt during passive tilt in roll (± 25º) increased on R+1 compared to preflight. However, the amplitude of perceived tilt during passive tilt in pitch (± 15º) did not change significantly on R+1 compared to preflight. The perceived amplitude of translation tended to increase during roll tilt and during pitch tilt after spaceflight. The perception of distances of visual targets ranging from 0.5 m to ~2 m was not affected by spaceflight. However, the distance of a visual target located at ~4 m was underestimated on R+1.

The eye movement data indicate that the amplitude of ocular counter-rolling during tilt in roll was reduced for several days after return from long-duration spaceflight. This decrease in amplitude was not accompanied by changes in the asymmetry of OCR (ocular counter rolling) between right and left head tilt (Reschke et al., 2018).

The translational vestibulo-ocular reflex (tVOR) measurements during vertical oscillations are being analyzed using a method that has been recently published (Clément et al., 2019). The tVOR at high frequency is an important otolith-mediated response to stabilize gaze during natural locomotion. A decrease in the tVOR gain could potentially alter gaze fixation during locomotion. Therefore, the results of this study have implications for a spaceflight-adapted vestibular system during locomotion.

When subjects imagined a laboratory-fixed target while being tilted in pitch at angles varying from 15º backward to 15º forward, the vertical eye position shifted downward ~5º compared to when they were actually looking at the target, thus indicating a downward shift of the subjective straight-ahead. The addition of a vibrotactile feedback of tilt when the subjects imagined the targets partially compensated for this downward shift of the subjective straight-ahead. This result confirms that a vibrotactile feedback is a useful countermeasure after landing for mitigating the effects of spaceflight on spatial disorientation and manual control (Clément et al., 2018; Reschke & Clément 2018).

Ground Control Study

Test-retest repeatability. A ground control study was completed to obtain normative data on 16 healthy non-astronaut subjects participating in three sessions similar to the astronaut preflight data sessions. A preliminary analysis comparing the responses of these 16 subjects across three sessions separated by about one month indicates that there is no learning effect induced by the repetition of the tests. In addition, the responses of the eight crewmembers tested preflight are within the range of those measured with the 16 non-astronaut subjects.

References

Reschke MF, Wood SJ, Clément G (2018) Ocular counter rolling in astronauts after short-and long-duration spaceflight. Scientific Reports8: 7747.

Clément G, Wood SJ, Paloski WE, Reschke MF (2019) Changes in gain of horizontal vestibulo-ocular reflex during spaceflight: Journal of Vestibular Research 29: 241-251.

Clément G, Reschke MF, Wood SJ (2018) Vibrotactile feedback improves manual control of tilt after spaceflight. Frontiers in Physiology 9: 1850.

Reschke MF, Clément G (2018) Vestibular and sensorimotor dysfunction during spaceflight. Current Pathobiology Reports6 (3): 177-183,

NOTE: End date changed to 9/30/2020 per L. Taylor/JSC (Ed., 8/23/18)

The subjective straight-ahead direction is a very basic perceptual reference for spatial orientation, movement, and locomotion. The perceived straight-ahead along the horizontal and vertical meridian is largely determined by both otolith and somatosensory inputs. Otolith and somatosensory inputs are altered in microgravity and will change this reference point. Adaptive processes are taking place within the central nervous system to take into account the new environment and compute new spatial egocentric and world-centered representations or frames of reference. This project will measure and monitor how these frames change over time by investigating eye movements and perceptual reports.

The three specific aims include:

Specific Aim 1: Near & Far Fixation. The first aim is to examine binocular eye movements when subjects fixate on actual targets (normal vision) and then imagine these same targets (occluded vision) in the straight-ahead direction relative to their heading. Initially the subjects’ gaze direction and fixation distance will be recorded as they explore the space around them using eye movements in darkness. Next they will be asked to fixate on straight ahead head-fixed targets located at near distance (arm’s length, ~0.5 m) and far distance (beyond 2 m). Responses will be compared with different tilt orientations, including pitch tilt forward and backward up to 15 deg. During separate trials, subjects will attempt to maintain fixation on a far Earth-fixed target with and without a vibrotactile sensory aid that indicates how far one has tilted relative to the straight ahead direction.

Specific Aim 2: Eye and Arm Movements. The second aim is to examine directed horizontal and vertical eye and arm movements, relative to Earth coordinates and relative to the subject’s head/body reference. This task will be performed with the subject upright and then tilted in roll directions up to 30 deg. The trajectory of directed eye and arm movements made in darkness are expected to reflect perceptual tilt errors.

Specific Aim 3: Near and Far VOR. The third aim is to examine the influence of target distance on the vestibulo-ocular reflex (VOR) during vertical translation movements. Subjects will stare at actual visual targets (normal vision) at various distances (near and far) in the straight-ahead direction while passively translated up and down using a spring-loaded chair. Vision will then be occluded, and the VOR will be recorded as the subject continues to fixate on the same target locations during translation. In addition to these periodic oscillations (~2.0 Hz), eye movements will also be recorded with vision during unpredictable passive head thrusts up and down using the spring-loaded chair.

For each of our specific aims above, our general hypothesis is that responses will be influenced by how accurately subjects perceive their spatial orientation. We will test this hypothesis by comparing responses with and without visual feedback. We also hypothesize for Specific Aim 1 that a vibrotactile sensory aid of tilt position will improve spatial orientation and this reduce gaze fixation errors.

Study Participants: Eight International Space Station (ISS) crewmembers will be recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+0/1 day, R+4 (±2) days, and R+8 (±2) days. Sixteen ground-based subjects will be recruited to participate in a ground control study for up to 3 sessions. A limited number of subjects will also participate in parabolic flight study as resources permit. This study is being implemented by the European Space Agency and is not carried in the U.S. ISS utilization plans.

Risk Characterization, Quantification\Evidence: This task will contribute to gap closure by providing information regarding any changes in an individual's egocentric reference that might have negative consequences on evaluating the direction of an approaching object or on the accuracy of reaching movements. This information is important for understanding the problems associated with long-term effects of microgravity on astronauts and how they re-adapt to the return of gravitational forces on Earth or other planetary surfaces.

Countermeasure\Prototype Hardware or Software: This task will contribute to gap closure by evaluating how a vibrotactile feedback of reference frames can be used to improve spatial orientation of fixation on space-fixed targets.

Flight Study

Eight International Space Station (ISS) crewmembers will be recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three post-flight sessions on R+0/1 day, R+4 (± 2) days, and R+8 (± 2) days. Preflight data was initiated in 2015 following approval for this study to be implemented for pre- and post-flight testing only. To date, five ISS crewmembers have completed pre- and post-flight data collection. Preflight data collection has been obtained from two other crewmembers, although one of these subjects was withdrawn from the study due to changes in post-flight test plans.

Preliminary analysis of the perception data indicates that the amplitude of perceived tilt and translation during passive roll tilt decreased on R+1 compared to preflight. However, the amplitude of perceived tilt and translation during passive pitch tilt was unchanged on R+1 compared to preflight. The perception of distances ranging from 0.5 m to 4 m was not affected by spaceflight.

The eye movement data are being analyzed using a method that has been recently published (Reschke et al. 2018). The amplitude of ocular counter-rolling reflex during roll tilt was reduced for several days after return from long-duration spaceflight. This decrease in amplitude was not accompanied by changes in the asymmetry of OCR between right and left head tilt (Reschke et al. 2018).

Ground Control Studies

A preliminary analysis comparing the responses of 16 healthy non-astronaut subjects across three sessions separated by about one month indicates that there is no learning effect induced by the repetition of the tests (Clément et al. 2018). In addition, the responses of the seven crewmembers tested preflight so far are within the range of those measured with the 16 non-astronaut subjects.

[Ed. note: see below Bibliography section for references]

The subjective straight-ahead direction is a very basic perceptual reference for spatial orientation, movement, and locomotion. The perceived straight-ahead along the horizontal and vertical meridian is largely determined by both otolith and somatosensory inputs. Otolith and somatosensory inputs are altered in microgravity and will change this reference point. Adaptive processes are taking place within the central nervous system to take into account the new environment and compute new spatial egocentric and world-centered representations or frames of reference. This project will measure and monitor how these frames change over time by investigating eye movements and perceptual reports.

The three specific aims include:

Specific Aim 1: Near & Far Fixation. The first aim is to examine binocular eye movements when subjects fixate on actual targets (normal vision) and then imagine these same targets (occluded vision) in the straight-ahead direction relative to their heading. Initially the subjects’ gaze direction and fixation distance will be recorded as they explore the space around them using eye movements in darkness. Next they will be asked to fixate on straight ahead head-fixed targets located at near distance (arm’s length, ~0.5 m) and far distance (beyond 2 m). Responses will be compared with different tilt orientations, including pitch tilt forward and backward up to 15 deg. During separate trials, subjects will attempt to maintain fixation on a far Earth-fixed target with and without a vibrotactile sensory aid that indicates how far one has tilted relative to the straight ahead direction.

Specific Aim 2: Eye and Arm Movements. The second aim is to examine directed horizontal and vertical eye and arm movements, relative to Earth coordinates and relative to the subject’s head/body reference. This task will be performed with the subject upright and then tilted in roll directions up to 30 deg. The trajectory of directed eye and arm movements made in darkness are expected to reflect perceptual tilt errors.

Specific Aim 3: Near and Far VOR. The third aim is to examine the influence of target distance on the vestibulo-ocular reflex (VOR) during vertical translation movements. Subjects will stare at actual visual targets (normal vision) at various distances (near and far) in the straight-ahead direction while passively translated up and down using a spring-loaded chair. Vision will then be occluded, and the VOR will be recorded as the subject continues to fixate on the same target locations during translation. In addition to these periodic oscillations (~2.0 Hz), eye movements will also be recorded with vision during unpredictable passive head thrusts up and down using the spring-loaded chair.

For each of our specific aims above, our general hypothesis is that responses will be influenced by how accurately subjects perceive their spatial orientation. We will test this hypothesis by comparing responses with and without visual feedback. We also hypothesize for Specific Aim 1 that a vibrotactile sensory aid of tilt position will improve spatial orientation and this reduce gaze fixation errors.

Study Participants: Eight International Space Station (ISS) crewmembers will be recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+0/1 day, R+4 (±2) days, and R+8 (±2) days. Sixteen ground-based subjects will be recruited to participate in a ground control study for up to 3 sessions. A limited number of subjects will also participate in parabolic flight study as resources permit. This study is being implemented by the European Space Agency and is not carried in the U.S. ISS utilization plans.

Risk Characterization, Quantification\Evidence: This task will contribute to gap closure by providing information regarding any changes in an individual's egocentric reference that might have negative consequences on evaluating the direction of an approaching object or on the accuracy of reaching movements. This information is important for understanding the problems associated with long-term effects of microgravity on astronauts and how they re-adapt to the return of gravitational forces on Earth or other planetary surfaces.

Countermeasure\Prototype Hardware or Software: This task will contribute to gap closure by evaluating how a vibrotactile feedback of reference frames can be used to improve spatial orientation of fixation on space-fixed targets.

Flight Study

Eight International Space Station (ISS) crewmembers will be recruited to participate in three preflight sessions (between 120 and 60 days before launch) and then three postflight sessions on R+0/1 day, R+4 (± 2) days, and R+8 (± 2) days (Clément and Wood 2016). Preflight data was initiated in 2015 following approval for this study to be implemented for pre- and post-flight testing only. To date, three ISS crewmember have completed pre- and post-flight data collection. Preflight data collection has been obtained from three other crewmembers, although one of these subjects was withdrawn from the study due to changes in post-flight test plans.

Ground Control Studies

Test-retest repeatability. This past year, a ground control study was completed to obtain normative data on 16 healthy non-astronaut subjects participating in three sessions similar to the astronaut preflight data sessions. A preliminary analysis comparing the responses of these 16 subjects across three sessions separated by about one month indicates that there is no learning effect induced by the repetition of the tests (Campbell et al. 2017). In addition, the responses of the five crewmembers tested preflight so far are within the range of those measured with the 16 non-astronaut subjects.

Translational Vestibulo-Ocular Reflex (tVOR). The tVOR is an important otolith-mediated response to stabilize gaze during natural locomotion. In the initial phase of this study, we began to examine an existing data set obtained during Off-Vertical Axis Rotation. In this data set, we were able to establish that the modulation of horizontal slow phase velocity was larger at higher frequencies (>0.8 Hz) than lower frequencies (<0.05 Hz). Previously described kinematic effects of fixation distance were not present for these lower frequencies (Douglas et al. 2017). Therefore, for our SAM study protocol, we limited the tVOR trials to only high frequency trials that simulate the kinematic demands of natural locomotion.

References

Clément GR, Wood SJ. Translational otolith-ocular reflex during off-vertical axis rotation in humans. Neurosci Lett. 2016 Mar 11;616:65-9.

Campbell D, Wood SJ, Reschke MF, Clément G (2017) Evaluating the subjective straight ahead before and after spaceflight. In: NASA Human Research Program Investigators’ Workshop, Galveston, Texas

Douglas SB, Clément G, Denise P, Wood SJ (2017) Ocular reflex phase during off-vertical axis rotation in humans is modified by head-turn-on-trunk position. Scientific Reports 7, 42071.