STEM Today,November 2017, No.26

STEM TODAY November 2017, No. 26

STEM TODAY November 2017, No. 26

CONTENTS SM2.1: Determine the changes in sensorimotor function over the course of a mission and during recovery after landing.

The most profound sensorimotor deficits occur during and after gravitational transitions. Given these changes there is a possibility that crew will experience impaired control of the spacecraft during landing along with impaired ability to immediately egress following a landing on a planetary surface (Earth or other) after long-duration space flight.

Editorial Editor: Mr. Abhishek Kumar Sinha Editor / Technical Advisor: Mr. Martin Cabaniss

STEM Today, November 2017, No.26

Disclaimer ( Non-Commercial Research and Educational Use ) STEM Today is dedicated to STEM Education and Human Spaceflight. This newsletter is designed for Teachers and Students with interests in Human Spaceflight and learning about NASA’s Human Research Roadmap. The opinion expressed in this newsletter is the opinion based on fact or knowledge gathered from various research articles. The results or information included in this newsletter are from various research articles and appropriate credits are added. The citation of articles is included in Reference Section. The newsletter is not sold for a profit or included in another media or publication that is sold for a profit.

Cover Page ISS024E006901 Flight engineer (co-pilot) Shannon Walker on-board the Russian Soyuz spacecraft, TMA-19 which launched on June 15, 2010.

Image Credit: NASA

Back Cover ISS025E018049 Shannon Walker looking out of the international space station’s cupola at the Caribbean view beneath.

Image Credit: NASA

STEM Today , November 2017

Editorial Dear Reader

STEM Today, November 2017, No.26

All young people should be prepared to think deeply and to think well so that they have the chance to become the innovators, educators, researchers, and leaders who can solve the most pressing challenges facing our world, both today and tomorrow. But, right now, not enough of our youth have access to quality STEM learning opportunities and too few students see these disciplines as springboards for their careers.

According to Marillyn Hewson, "Our children - the elementary, middle and high school students of today - make up a generation that will change our universe forever. This is the generation that will walk on Mars, explore deep space and unlock mysteries that we can’t yet imagine". "They won’t get there alone. It is our job to prepare, inspire and equip them to build the future - and that’s exactly what Generation Beyond is designed to do."

STEM Today will inspire and educate people about Spaceflight and effects of Spaceflight on Astronauts.

Editor Mr. Abhishek Kumar Sinha

Editorial Dear Reader The Science, Technology, Engineering and Math (STEM) program is designed to inspire the next generation of innovators, explorers, inventors and pioneers to pursue STEM careers.

According to former President Barack Obama, " Science is more than a school subject, or the periodic table, or the properties of waves. It is an approach to the world, a critical way to understand and explore and engage with the world, and then have the capacity to change that world..."

STEM Today addresses the inadequate number of teachers skilled to educate in Human Spaceflight. It will prepare , inspire and educate teachers about Spaceflight. STEM Today will focus on NASA’S Human Research Roadmap. It will research on long duration spaceflight and put together latest research in Human Spaceflight in its monthly newsletter.

Editor / Technical Advisor Mr. Martin Cabaniss

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Human Health Countermeasures (HHC) SM2.1: Determine the changes in sensorimotor function over the course of a mission and during recovery after landing

The most profound sensorimotor de cits occur during and after gravitational transitions. Given these changes there is a possibility that crew will experience impaired control of the spacecraft during landing along with impaired ability to immediately egress following a landing on a planetary surface (Earth or other) after long-duration space ight.

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Eye-Head Coordination in Space Shuttle Astronauts

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The objective of this study was to assess how astronauts perform a visual task that was required to pilot and land the Space Shuttle. Reschke et.al. measured the eye and head movements of pilots as they acquired specific visual targets in the horizontal plane before and after they participated in a Space Shuttle mission of 6 to 17 days.

A total of 31 healthy human subjects (29 male, 2 female) participated in the study; their mean age was 41.1 years (SD = 5.9), with ages ranging from 33 to 58 years. The subjects were Space Shuttle commanders, pilots, or mission specialists with professional piloting experience. Subjects participated in one of 17 Space Shuttle missions lasting 6 days to 17 days. Eight subjects participated in one of 6 missions lasting from 6 to 9 days (mean 8.4); 14 subjects participated in one of 6 missions lasting from 10 to 12 days (mean 11.0); and 9 subjects participated in one of 5 missions lasting from 14 to 17 days (mean 15.0). As shown in Fig. 1, flight duration increased progressively during the Extended Duration Orbiter Program, starting with STS-36 (4.5 days) and culminating with STS-72 (17 days). The investigation presented here began about 18 months into the program and was conducted from November 1991 to January 1996.

Results Eye-head coordination While acquiring images 20◦ and 30◦ off center in the horizontal plane, the eyes and the head make one single movement to the target. The head, having greater inertia than the eye, typically moves after the eye has moved in the orbit. Gaze is the direction of the visual axis with respect to space, which is defined as the sum of eye position with respect to the head, and head position with respect to space. At the end of the eye saccade the gaze has already reached its final position, but the head continues to move. The head movement stimulates the horizontal semicircular canals and produces an eye movement through the vestibulo-ocular reflex that is opposite in direction and velocity to that of the head. When moving to a target that is offset 60◦ , the gaze often undershoots the target by 5-10◦ and a corrective eye saccade occurs to reposition the gaze onto the target.

In general, the total gaze movement is greater than the total head movement, so that the final position of the eye is offset in the direction of head movement. Comparison of the recordings obtained before and immedi-

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ately after flight indicated that the amplitudes of the initial eye saccade and head movement were smaller and the duration of gaze movement to the target was longer after flight than before flight (Fig. 2).

Gaze latency The delay between the start of the eye and head movements after flight (R + 0: 24.9 ± 32.4 ms) was not significantly different from the delay before flight (19.4 ± 25.6 ms), when the subjects took 350 to 440 ms to reach the target. This gaze latency increased as a function of the angular position of the target (Fig. 3). The effects of spaceflight on gaze latency were analyzed using a 3 targets (20◦ , 30◦ , 60◦ ) X 4 sessions (Pre, R + 0, R + 2, R + 4) repeated-measures ANOVA, alpha = 0.05. There was a significant effect of target position [F (2,360) = 29.74, P < 0.001] and a significant effect of spaceflight [F (3,360) = 2.76, P = 0.04] on gaze latency, but no significant interaction between target position and spaceflight [F (6,360) = 0.05, P = 0.99]. An increase in gaze latency was observed in more than two-thirds of the subjects on R + 0. The largest increase relative to preflight latency was 172 ms. When averaged across all subjects, the gaze latency for reaching the 30◦ and 60◦ targets increased relative to preflight latency by 34 ms (P = 0.024) and 30 ms (P = 0.006), respectively. Responses had returned to baseline on R + 2.

Eye and head velocity The time to bring gaze on target is determined by the maximal eye and head velocities. Before the flight the mean peak velocities of the initial eye saccade were 363.4◦ /s (SD = 54.7), 374.6◦ /s (SD = 60.7), and 382.3◦ /s (SD = 68.1) for the targets at 20◦ , 30◦ , and 60◦ respectively (Fig. 4A). A two-way repeated-measure ANOVA indicated a significant effect of spaceflight [F (3,360) = 6.91, P < 0.001] on peak eye velocity, and no difference between the targets [F (2,360) = 1.02, P = 0.36]. On R + 0, the peak eye velocity when acquiring for the 30◦ and 60◦ targets decreased relative to preflight peak velocity by 26.0◦ /s (P < 0.01) and 36.4◦ /s (P < 0.01), respectively. Responses had returned to baseline on R + 2.

The peak head velocity was related to position of the target; the more offset the target, the faster the head movement (Fig. 4B). A two-way repeated-measure ANOVA indicated a significant difference in peak head veSTEM Today Page 5

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locity between the targets [F (2,360) = 256.3, P < 0.001] and a significant effect of spaceflight [F (3,360) = 4.50, P < 0.01]. On R + 0, the peak head velocity when acquiring the targets at 20◦ , 30◦ , and 60◦ decreased relative to preflight peak velocity by 10.0◦ /s (P < 0.01), 6.9◦ /s (P < 0.02), and 6.7◦ /s (P < 0.05), respectively.

On R + 2, the peak head velocity was still significantly slower than preflight peak velocity (P < 0.02) when acquiring the 30◦ targets, whereas the responses for acquiring the other targets had returned to baseline.

Eye and head amplitude Repeated-measures ANOVA indicated a significant effect of target position on the peak amplitudes of the eye saccade [F (2,360) = 864.8, P < 0.001] and head movement [F (2,360) = 1067, P < 0.001]). Spaceflight affected the peak amplitude of the head movement [F (3,360) = 4.38, P < 0.01], but not the peak amplitude of the eye saccade (Fig. 4C). Relative to preflight values, the head amplitude decreased on R + 0 by 1.5◦ -2.2◦ (P < 0.05) depending on the target offset (Fig. 4D).

During both preflight and postflight tests, the gaze displacement remained essentially constant after the initial eye saccade ended (Fig. 2), indicating that the slow-phase eye compensation was very precise. During this phase of the response, the vestibulo-ocular reflex gain (ratio of eye velocity and head velocity) was near unity across all targets and test sessions. In addition, the number and amplitude of the corrective saccades at the end of the head movement toward the 60◦ targets were not significantly affected by spaceflight.

Repeated-measures ANOVA indicated an effect of spaceflight on the final position of the eye in the orbit [F (3,360) = 3.16, P < 0.03] (Fig. 4E) and on the final position of the head in space [F (3,360) = 3.51, P < 0.02] (Fig. 4F). Post-hoc tests revealed that the final eye position during acquisition of the 20◦ target was significantly larger on R + 0 (P < 0.01), R + 2 (P < 0.001), and R + 4 (P < 0.001) compared to preflight.

This effect was also observed during acquisition of the 30◦ target on R + 2 (P < 0.01) and R + 4 (P < 0.01). The final head position during acquisition of the 20◦ target was significantly smaller than preflight on R + 0 (P < 0.001). This effect was also observed during acquisition of the 30◦ target on R + 0 (P < 0.001) and R + 2 (P < 0.001).

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Effect of flight duration Figure 5A indicates that the increase in gaze latency immediately after landing (see Fig. 3) was not correlated with the duration of the flight. Each subject’s responses during visual target acquisition after spaceflight were normalized for each visual target according to their mean gaze latency before flight. Individual responses were then grouped by flight duration into 3 categories (short: 6-9 days; medium: 10-12 days; long: 13-17 days), and the group mean was calculated for each test session. The effects of spaceflight duration on the gaze latency were analyzed using repeated-measures ANOVA with 3 targets (20◦ , 30◦ , 60◦ ) X 3 durations (short, medium, long). There was no significant effect of target [F (2,360) = 0.23, P = 0.79] or spaceflight duration [F (2,360) = 1.41, P = 0.26] on gaze latency. Figure 5B illustrates mean gaze latencies for acquiring the 60◦ visual target (group average) after short, medium, and long duration space missions.

• The results of this study indicate that the time to acquire a visual target located 30◦ and 60◦ off center in the horizontal plane increased by 7-10% (30-34 ms) during the first few hours after return form space.

This could potentially result in piloting errors because the astronauts will experience delays capturing operationally relevant targets during the critical period when they are returning to Earth.

• Time delays to acquire visual targets were consistent after short (6-9 days), medium (10-13 days), and long (14-17 days) duration Space Shuttle missions.

• Responses returned to normal 48 hours after landing. The increase in gaze latency was attributed to a decrease in velocity and amplitude of both the initial eye saccade and head movement toward the target.

• On Earth, the otoliths help the brain interpret the position of the head in space by detecting head tilt relative to gravity. In the absence of a gravitational reference during spaceflight, the static otolith signals are no longer effective, and visual and proprioceptive cues are primarily used to interpret the position of the head. During return to a 1g environment, otolith inputs are restored and proprioceptive information STEM Today Page 7

changes. Recent clinical studies suggest that altered vestibular and somatosensory inputs may lead to changes in an individual’s mental representation of space. A misinterpretation of the head’s position in space could result in a misperception of gaze position, which would slow head and eye movement while acquiring visual targets.

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• Altered visually-guided saccades, vestibulo-ocular reflex, and eye-hand coordination strategies have also been observed during exposure to very brief periods (20 s) of microgravity and hypergravity during parabolic flight.

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Head/body movements in NASA Mir-Phase 1 Mission

Between March 1995 and June 1998, seven NASA astronauts flew on the Russian Mir space station, as "Phase 1" of the joint effort to build the International Space Station, and provided NASA with invaluable experience on the operational and biomedical problems associated with flights of up to six months in duration.

Jason T. Richards has provided a summary of the available information on neurovestibular dysfunction, space motion sickness, and readaptation to Earth’s gravity on the NASA Mir flights, based on a set of medical questionnaire data, transcripts, and interviews which are available from the NASA-Mir Phase I program in his paper "Neurovestibular Effects of Long-Duration Spaceflight: A Summary of Mir-Phase 1 Experiences".

Head/body movements provoke motion sickness symptoms The following are the flight surgeon’s notes regarding one crewmember’s apparent functioning on landing day: • Egress movements and removal of Advanced Crew Escape Suit (ACES) provoked neurovestibular symptoms (dizziness).

• Neurovestibular symptoms were exacerbated by head movements.

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• General condition: Looked very good. Not sweaty, pale, etc., but dizzy and nauseated with head movements.

• Was not able to [be a subject in postflight science experiments] because of neurovestibular symptoms.

• Remarkable orthostatic stability, seemed to quickly adapt in first hour or so post-landing, but prominent neurovestibular symptoms, with nausea and emesis provoked by head movements and overall movements requiring motor control. Passive [movements] ok.

Furthermore, this crewmember did not do the walk-around (stayed on the Astro-van, or CTV). On the CTV, coming off the orbiter, this crewmember started doing head movements and got motion sick. According to the flight surgeon, this crewmember will tell you, "I got severely motion sick like I was on a carnival ride." As soon as the CTV started pulling back with that motion this crewmember was vomiting. In fact, the crewmember vomited every time he had to move, even without head movements.

This crewmember’s flight surgeon was interviewed: Interviewer: "Now when [the crewmember] was just lying there, could he move his head and get the same symptoms ?"

Surgeon: "Lying, not moving, [the crewmember] was fine. I think if you moved I the crewmember] on the gurney, he felt sick. There may have been an orthostatic component, but [the crewmember] didn’t really have any orthostasis ... he felt sick and couldn’t even stand. He couldn’t do neurovestibular tests, which required a lot of head movements up, down, back and forth."

Surgeon: "[The crewmember] threw up once on the CTV, and then was looking pretty good, and then it was getting him off the CTV, seeing ... family, getting ... into ... room, and he got sick again getting up, and I said ‘how about some Meclizine’ and he said that’s a dumb idea, because I’m just going to throw it up.’ I gave ... one - he threw it up" Another crewmember was stunned at the magnitude of symptoms experienced on landing day and found that nothing helped to alleviate them. This crewmember did not premedicate before entry.

A third crewmember’s flight surgeon made the following notes on landing day: Wheelstop+27 min. Sitting up with feet 90 deg down on floor, [the crewmember] notes that pitch and yaw [head] movements [are] OK, but roll is notably provocative. +33 min. Walking to hatch with assist, turning to hatch to lie backwards +47 min. Having persistent emesis, still seated in recliner +56 min. Persistent [neurovestibular symptoms], [the crewmember] was given Phenergan 50 mg IM; moved off to gurney, starboard side of CTV

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A third crewmember noted that 1) not standing motionless; 2) lying, sitting, or walking; and 3) keeping head still [helped] minimize neurovestibular symptoms. He also noted that standing motionless and rapid, unexpected head movements exacerbated symptoms.

A fourth crewmember noted that being prone made landing day symptoms better and added that "being on my back was a piece of cake." When asked what made his landing day symptoms worse, he responded, "Four months in space. Long duration flight as opposed to a Shuttle mission.... Every time I turned my body up I started to get this stomach awareness and ... that was what I was ... worried about."

Surgeon: "Phenergan IM 12.5 mg [was] given shortly before... probably helped, and [the crewmember was] able to walk from crew quarters to the suit room [at wheelstop+06:30]. Additional 25 mg [of Phenergan was] given thereafter and [the crewmember] was allowed to sleep for several hours."

Surgeon: "If I had to do again, I would give someone IM Phenergan and be done with it. I think I gave [the crewmember] a homeopathic 12.5 [mg] IM of Phenergan to try and get [the crewmember] down the hall to sit there and talk. So he did that, and then I gave ... another 25 or 30ish and he slept for a couple of hours until ( later] that night. [The crewmember] was feeling better."

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Illusory sensations during head movements Surgeon: "[An onlooker] was looking at [the crewmember’s] face - I was behind him - and [the onlooker] looked at me going (hand motions) meaning [the crewmember’s] gyros were spinning."

Interviewer: "Did [the crewmember] have any persistent vection illusions? Or pitchforward illusions?"

Surgeon: "[The crewmember] said very little. Very little."

One crewmember commented: "I turn my head slightly to the right and down in order to place my helmet on the deck beside me. I immediately feel as if I am doing backward somersaults, spinning tight and fast. I make a mental note not to move my head abruptly and to avoid any further bending or twisting...."

"I turn to the left and start shuffling toward the forward bulkhead with neck braced... At the forward bulkhead I grab on and turn ninety degrees to the left again. Some spinning, but not severe.... I shuffle to the hatch, bend down on my knees, and after momentarily feeling like I am tumbling again..." "Because the force of earth’s gravity was still very new to me, I felt as though I were spinning and tumbling whenever I moved my head abruptly or leaned forward. These sensations were mildly nauseating." "... going around any corner provoked the sensation of a delayed tumble ..."

"One by one, people moved in behind my chair to get a picture with [me].... they would inevitably put their hand on the back of the chair which was designed to respond to such pressure by tilting back an inch or two.

This slight chair tilt [made me feel like] I was doing a back flip."

In a post-flight interview, a second crewmember described his illusory sensations: Interviewer: "When you make head movements, are you experiencing any kind of linear translation in the movement, either of yourself or of the visual surround?"

Crewmember: "... I do when I turn..."

Interviewer: "Its rotational?

Crewmember: "Yes." Interviewer: "On your motions ... do they feel greatly exaggerated with a small head movement?"

Crewmember: "Uh-huh."

Interviewer: "Are there any delays?"

Crewmember: "I have a general lethargy, yeah. Its like ... everything’s slow."

Interviewer: "When you do make a head movement, though, do you feel like, for example, the motion as continuing, even though you know that the head movement has stopped."

Crewmember: "I had that a lot yesterday. Don’t have it too much today. A little bit."

Gaze holding problems This same crewmember went on to say: Interviewer: "You felt like you know where the target was pretty much?"

Crewmember: "Yeah, I would find that my concentration was not always [focused]... and my vision would wander..."

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Interviewer: "Were you losing the target a lot when it was [not visible]?"

Crewmember: "When it was gone, yeah... I’d find my concentration was not good."

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Balance and locomotion problems One crewmember recalled: "I had a real sensation that if I were to bend forward, if I weren’t careful. I’d continue forward, and if I bent back, if I weren’t careful I’d continue back, and the usual problem of going down a hall, and if you had to make a ... left or right turn, you would tend to overshoot. You’d tend to brush your shoulder on the opposite wall. You just don’t turn sharply enough..."

Scores from the Neurologic Function Exam were recorded for 3 crewmembers on R+0 and only 2 crewmembers on R+3 and are shown in Table 3.3.

Postflight ncurovestibular disturbances: R+1 - R+7 Increased sensitivity to g-forces The sensation of enormous weight continued all day (R+0) for one crewmember. Even later, as he was eating dinner, he’d sit up, eat some food, and then have to go lay down and rest for some minutes before sitting up and trying again. Even lying supine in bed that night, he felt the huge g-force pushing him down into the mattress.

But, the next day was better, and by 24 hours postlanding, the subjective strength of gravity had notably abated.

Another crewmember described the experience this way: "Gravity now yanked me into the mattress.... Getting smashed into the mattress in turn created a sensation of pressure on my body ... [that] would translate into a propulsive force [if I were in space]. It felt ... that I would, at any moment, be thrust out of bed and toward the ceiling.... whenever I would drift off closer to sleep.... [To

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combat this feeling], I rolled the sheet into a sort of rope, positioned it firmly across my waist, and tucked the loose ends of the sheet under the mattress. With the sheet now holding me in place as an improvised restraint, ... my mind was put at ease and I relaxed enough to fall asleep." This crewmember’s head felt heavy when lying on a pillow, and he had a sense of sinking into the bed until R+4.

Head/body movements provoke illusions and motion sickness symptoms A flight surgeon was asked: "How long would you say before [the crewmember] got rid of all neurovestibular [symptoms]...?

Surgeon: Well, [the crewmember] went back to bed then, and the next morning he got up, was doing better, but still was kind of [woozy]..., had breakfast, ... and ... was still a little nauseated even with walking. Came back up, ... about four hours prior to landing (of the Gulfstream 2 aircraft taking the crewmember back to Ellington), ... I gave [the crewmember] another 25 to 30 mg of Phenergan.... [The crewmember] ... didn’t get sick on the plane, and ... motion sickness began to wane and never came back.

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Another crewmember experienced Earth sickness for a day or two. This crewmember said that lying horizontal helped to alleviate landing day symptoms. Rapid head movement, tilting head forward to look at the ground, and rapid turn of the body and/or head made landing day symptoms worse. Nodding and moving the head reportedly made post-flight recovery symptoms worse. He took two 50-mg doses of Meclizine on R+l at 22:00 and 23:00 in order to alleviate neurovestibular symptoms. Both doses were scored to be "somewhat effective" and made him feel drowsy. AIcohol consumption was reported to help alleviate neurovestibular symptoms as well. This crewmember had strong translation illusions after head tilt on landing day, which abated over a week.

The crewmember provided the following description: "As on a previous short mission, a classic tilt translation was my dominant vestibular effect upon return. When I tilted my head to the right, I felt I was translating to the left through a distance so large I thought I was in the next room. It was equal in all 4 directions and approximately double the intensity after the extended duration mission as compared with an earlier short mission. The decay of the effect seemed exponential with a tirne constant of 1 day and therefore the effects were reduced by 98% in 4 days. This ’decay’ rate was the same for the long and short missions."

Balance and locomotion problems Some of the crewmembers’ balance control performances on computerized posturography tests on R+1 were among the lowest equilibrium scores (i.e. worst) ever recorded in the Neurosciences Lab at JSC. New motor control strategies (co-contraction strategies) seem to emerge early after flight and persist for many days. One crewmember made the following comments: "On every one of my ... Shuttle flights, on waking up the morning after we landed, I couldn’t even tell I’d been in space, but it was five days before [I felt I had normal balance] after Mir." "I jogged three miles, and that’s five days after we landed. It was the hardest three miles I ever did..."

"We heard about people [who had returned from Skylab] that fell in showers or had balance problems."

A flight surgeon made the following comments regarding a second crewmember: [’The crewmember] was still really wobbly - [the crewmember] looked drunk the first day ... [his] feet would keep slapping the floor. [The crewmember] just couldn’t get ... [his] feet up to walk... So ... I had my hand around [the crewmember’s] hip for the first day, day and a half. [When the returning crewmember] got off the plane [at Ellington Field in Houston], ... and walked into the house, [the crewmember] was walking unassisted, wobbling some... They landed [from orbit] Thursday evening, this was Friday, and by Monday you really couldn’t tell.

A third crewmember noted that rounding corners was hard. He reported that you over-perceive the turn acceleration and flatten out the radius of turn, so you walk wide, and bang into door frames as you go around corners. You feel like a klutz. On R+3, this crewmember reported his level of function to be 40% of normal.

This crewmember reported to be cognitively in tune and sharp in flight. Post-flight, cognitive functioning was worse due to distractions caused by neurovestibular effects - it felt like the flu. Further, he felt like his ability to [control advanced body movements], bench press, and walk were 0%, 20%, and 80% of normal, respectively.

Postflight neurovestibular disturbances: after R +7 Increased sensitivitv to 2-forces "The spray of water from the shower was like pellets bombarding my body. I felt as if I would be sent tumbling....

By the end of the second month of rehab, ... I would shower - no longer feeling as if bullets were riddling my body..."

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Another crewmember noted that, even a month after landing, heaviness of limbs and objects was noticeable.

This crewmember also responded: Interviewer: "How long was it after you landed that you felt like you were back to your old self?"

Crewmember: "[I’ve been back] five months now. I’m, I’d say, 80 or 90 percent back."

Postural control and balance disturbances Compared to short-duration space flight, long-duration crewmembers exhibit greater alterations in sensorymotor function on return to Earth. These changes impact the ability to maintain postural and locomotor control along with compromising the capacity of crewmembers to visually acquire targets leading to extremely delayed responses and visual problems during head and body movements following return to Earth. There appeared to be an initial recovery period of several days as demonstrated by a clinical exam of gross neurologic function.

Residual, subclinical neurovestibular impairment was demonstrated in the posture platform, dynamic visual acuity, and gaze stability tests, indicating a slower return to baseline. Full recovery, as measured by the posture platform, took up to 4 weeks.

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Effects on eye-head coordination seen on long-duration missions (e.g., delayed target acquisition, reduced head velocity following flight, high gain in the visual vestibulo-ocular system, and failure to suppress the vestibuloocular response (VOR) during head/eye target pursuit) were longer lasting for long-duration missions than for short-duration. Recovery, particularly in the pursuit system, was not observed in some crewmembers even 64 days following flight. There is significant alteration in head-trunk coordination during locomotion following long-duration space flight.

At least one crewmember showed disruption in lower limb muscle activation patterns during locomotion that exceeds that shown by Shuttle crewmembers. One crewmember said that even at 5 weeks postflight, he was sometimes still "wobbly". His strength was normal, so he was convinced it was a control problem, and he has not noticed any unusual problems with gait initiation. Finally, at 10 weeks, he was feeling pretty good. Another crewmember had "flutters" of vestibular uncertainty that continued for several months. He did not want to fly [an aerobatic aircraft] solo for two months because he just was not confident.

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Neurovestibular Symptoms in Astronauts Immediately after Space Shuttle and ISS Missions

Millard F. Reschke and other authors performed a study to assess symptoms that might impede an astronaut’s ability to exit the vehicle unassisted after landing and published the results in their paper "Neurovestibular Symptoms in Astronauts Immediately after Space Shuttle and International Space Station Missions".

Subjects: The Space Shuttle crewmembers included 12 men and 2 women (mean ± SD age, 42.4 ± 5.0 years) who flew on 3 missions that lasted about 1 week (mean duration, 7.4 ± 0.9 days). Four crewmembers were participating in their first space mission, and the remaining 10 had flown on at least 1 other occasion.

The ISS crewmembers included 16 men and 2 women (mean age, 45.5 ± 6.1 years) who were transported to and from the ISS on 8 Soyuz missions for missions that lasted about 6 months (mean duration, 175.8 ± 13.7 days). Seven crewmembers were participating in their first space missions, and 11 had flown on at least 1 other occasion.

Result: Vestibular and Motor Function Tests Table 3 shows the number of Space Shuttle and ISS subjects with positive results for each test. To compare the responses of the Space Shuttle and ISS subject groups, Fisher’s exact test was calculated for 2 X 2 contingency tables. Indeed, for comparing proportions between 2 populations, Fisher’s exact test tends to be more accurate than Pearson’s chi-square test when samples of 2 small populations are compared. The main observations are summarized as follows: • All Space Shuttle subjects had normal test results for saccade and pursuit tracking.

• One Space Shuttle subject had an upbeating positional nystagmus when sitting upright that was detected through Frenzel goggles but considered to be within reference range. Attempts to induce paroxysmal positional nystagmus were negative for the 2 Space Shuttle subjects tested with the Dix Hallpike maneuve.

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• Gaze-evoked nystagmus with prolonged gaze holding at large lateral and upward eccentricities was noted in 29% of Space Shuttle subjects and 38% of ISS subjects.

• The most common abnormal finding was the incapacity to walk heel to toe along a straight line without stumbling or falling. This difficulty was demonstrated by 79% of Space Shuttle subjects and all 9 ISS subjects tested (100%). All subjects demonstrated abnormal broad-based gait during normal walking. The typical distance between the feet was 45 cm.

• The next-most common abnormality, dysmetria during the pointing test, was exhibited by 71% of the Space Shuttle subject and 57% of the ISS subjects during their first few attempts at finger-tonose testing.

All subjects achieved the target by the third to fifth attempts.

• All subjects but 1 reported that standing immediately after landing required extraordinary effort. Fiftyseven percent of Space Shuttle subjects and 29% of ISS subjects could not stand from a seated position without assistance. Orthostatic intolerance, decrease in muscular strength, and microgravity induced changes in central muscular coordination contributed to this deficiency.

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• Postural instability during the standing test was positive for 36% of the Space Shuttle subjects and 31% of the ISS subjects. The ISS crewmembers who were tested immediately after landing (i.e., after the same delay as for the Space Shuttle crewmembers) did not have difficulties in maintaining upright balance.

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Subjective Reports All subjects reported feeling unstable or unbalanced when walking, particularly when making turns. Four Space Shuttle subjects had headaches after landing, and 3 subjects reported having had headaches during the first 2 or 3 days of flight. Postflight headache in 1 of these individuals was related to position (worse when upright, relieved upon lying supine). Only 1 ISS crewmember reported headache after landing. All 16 ISS subjects reported being nauseated immediately after landing. In addition to these 16 subjects, 2 other crewmembers could not be tested in the tent or at the airport because of severe reentry motion sickness symptoms.

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Interestingly, none of the Space Shuttle crewmembers had symptoms of reentry motion sickness after landing. However, 7 Space Shuttle subjects reported being nauseated, an indicator of space motion sickness, during the first few days of flight.

Unfortunately, in-flight reports of symptoms were not available for ISS crewmembers. Fifty percent of Space Shuttle subjects and 75% of ISS subjects perceived motion of the environment or their body when they moved their head. Translational movements along the foreaft, lateral, or vertical axis produced a sense of accentuated motion in that direction. One subject bent forward to counteract the sensation of falling in that direction and needed to straighten up abruptly to avoid falling.

While Space Shuttle subjects stooped during postflight testing, they felt that the floor was "rushing up to meet them," a symptom that has been reported previously. This sensation ceased immediately when body or head motion stopped.

Other symptoms described by Space Shuttle crewmembers included foot tingling when pressure was applied to the soles of the feet during reentry but not when walking after landing. Skin sensitivity changes have been reported in several other short-duration missions. Although ISS subjects did not report a tingling sensation in their feet, they all reported that their head and limbs felt very heavy after landing. None of the subjects reported diplopia, or double vision.

This study shows that the percentage of crewmembers with symptoms of vestibular disorders was similar after long-duration ISS missions and short-duration Space Shuttle missions, with the exception of reentry motion sickness. Russian investigators previously reported that motion sickness during reentry affects 27% of the cosmonauts after short-duration missions (4-14 days) and 92% after longer duration missions (several months to 1 year). This is verified by authors for ISS missions.

The percentage of Space Shuttle subjects who had symptoms of vestibular disorders in this study is similar to that reported for studies of 112 astronauts who flew on the Space Shuttle between 1996 and 2000. In these previous studies, the most frequent symptoms of vestibular disorders were persisting sensation aftereffects (60%), difficulty walking in a straight line (57%), unstable balance (48%), imprecise finger-to-nose pointing (20%), and use of arms for rising from a chair (14%).

Space Shuttle and ISS subjects would both have serious difficulties egressing a spacecraft without assistance soon after landing in case of an emergency. A previous report estimated that 5% to 15% of Space Shuttle crewmembers would be unable to egress the Space Shuttle due to neurovestibular symptoms and orthostatic intolerance after landing. Since ISS crewmembers have a greater incidence of reentry-induced motion sickness, this might exacerbate performance of an emergency egress after long-duration missions.

The 2 most frequent findings in this study were postural instability and reports of illusory sensations that the STEM Today Page 15

self or the environment was moving during rapid movements of the head or torso. Postural abnormalities during the immediate postlanding period have been documented and are generally believed to reflect disturbances in vestibular or proprioceptive function.

Although the time required to leave the spacecraft unassisted after landing has not been systematically measured, for obvious safety constraints, there has been casual observations by the crews. For example, during return of Expedition 6 from the ISS, a technical malfunction caused the Soyuz spacecraft to land some 460 km away from its planned touchdown point. The 5-hour delay for arrival of the ground support team gave the crew an opportunity to open the hatch, unstrap, and egress the Soyuz spacecraft without any outside help.

Expedition 6

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Due to the space shuttle Columbia accident, Expedition 6 was extended in duration to 5 1/2 months. The crew returned on a Soyuz spacecraft that landed in Kazakhstan. A spacecraft malfunction causing a ballistic entry displaced the landing site about 475 kilometers off course resulting in about a 5 hour delay for arrival of the ground support team. This gave the crew an opportunity to perform spacecraft safing, egress, and set up survival gear without any outside help.

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Don Pettit explained his perspective in the paper "Mars Landing on Earth: An Astronautâ&#x20AC;&#x2122;s Perspective". Our Soyuz was TMA-1, the first flight vehicle off the production line in 25 years with a major upgrade to the cockpit.

During entry, shortly after spacecraft separation from its propulsion and orbital modules, a small malfunction in a signal processing box that converts computer commands into jet firing signals caused us to loose the reaction control system (it is not known to the author if this malfunction was the result of the cockpit upgrade).

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This malfunction occurred when we were out of radio contact with mission control. We downmoded to an unguided ballistic entry where we experienced over 8 g loadings and landed about 475 kilometers short of the nominal landing site. Following the initial landing impact, our capsule rolled a few times and ended up on its side about 30 meters from the point of touchdown. The trajectory brought us out of radio range for the parachute phase line-of-sight VHF radios, thus, the ground support team had no idea where we had landed.

About two hours postlanding a search airplane flew overhead and we were able to make radio contact. About 3 hours after radio contact, the ground support personnel arrived via helicopter.

Due to these series of events, we as a crew performed a number of operational tasks previously not required by long duration crews. Given our sudden transitions from long term weightlessness, to 8 gâ&#x20AC;&#x2122;s, to the big thump, to being on our own in Kazakhstan, these tasks were physically taxing and not easy to accomplish. However, by working as a crew in this degraded state, we were able to take care of ourselves and complete basic survival tasks without outside help. We were not quivering sacks of Jell-O. This was due in part to the advancement in physiological countermeasures made on the International Space Station.

While on our own we performed a number of basic operational tasks. We performed spacecraft safing. This involves reading procedures (in Russian), flipping switches, and pushing buttons on the control panel to power down unneeded equipment so that battery life for radio operations can be extended. Since the Soyuz capsule ended on its side, our operations were done from a position of being strapped into a seat fixed on a slanted STEM Today Page 17

ceiling. We opened the hatch, unstrapped, and crawled out.

Following egress, we deployed the survival gear that was stowed in numerous small bundles throughout the spacecraft. Included were warm woolen cloths, food, water, a medical kit, a portable radio, and a signaling kit that contained a shotgun pistol that can fire flares as well as shotgun cartridges. Setting up a radio beacon was a priority.

We deployed two radio systems. One was a small VHF hand held radio that required assembly with its battery pack (transmitting power was 0.15 watt) and another that used the Soyuz VHF radio system with an external antenna. The antenna resembled a long, self-erecting tent pole and was bolted to a fixture on the hatch ring. There were no rescue aircraft within range. We unpacked food and water but no one was hungry. When the helicopters came near we fired a volley of flares from the shotgun pistol to signal our location.

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Performing these basic survival tasks was not easy. Moving was provocative. Your vestibular apparatus bitterly complained when there was head movement. Of the three of us, my symptoms were the greatest which is not uncommon for a rookie. Apparently, your body remembers the trials of past space flights making each additional one easier. For my crewmates, walking was labored but was done as needed shortly after landing. I had trouble walking but could crawl. By crawling back and forth between our Soyuz capsule and our mounting pile of survival gear I was able to contribute to our "base camp".

There were no systemic aches or pains associated with movement. We had good muscle strength. We had the lean muscled look of someone coming home from health camp, not the muscle-atrophied bodies from historic long duration space flight. My limbs felt heavy because my brain was not yet compensating for their weight.

Like an electronic scale that tares out the weight of the beaker so that only the contents is weighed, your brain normally subtracts the weight of your limbs from the gravity equation so you primarily feel the weight that you hold.

Upon returning, the brain had not yet kicked in this compensation which takes about 10 to 15 hours. Slow and deliberate motions were readily made with sufficient motor control to connect electrical wire harnesses, antennas, cycle switches on control panels, and shoot a shotgun pistol. Motor control for operating the spacecraft mechanisms and survival gear was not a problem. However, fast coordinated movement was not possible for me.

We were able to accomplish the necessary operations by working as a team where we each contributed within our current physical ability. Perhaps most important, we were each able to take care of our personal needs; a down crewmember requiring care from a second person would have effectively reduced our crew of three to a crew of one.

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Effects of long-duration space flight on target acquisition

The purpose of this was to explore the effects of long-duration space flight on the acquisition of specific visual targets in the horizontal plane. Seven cosmonauts (4 high performance pilots and 3 non-pilots) who had flown between 186-198 days on Mir station served as subjects. The median age of the subjects was approximately 51 yrs. All subjects had the equivalent of an Air Force Class I physical.

Baseline testing was performed 4 times prior to launch and 4 times following landing at different intervals totrack recovery. During testing the subjects were required to acquire targets that were randomly presented with both a head and eye movement using a time optimal strategy. Prior to flight two unique head movement strategies, related primarily to piloting experience, were used for target acquisition. Non-pilots employed a Type-I strategy consisting of high velocity head movements with large peak amplitudes, while high performance pilots used primarily low velocity, small amplitude head movements (Type-II) to acquire the targets (p < 0.02).

Results Before flight, all cosmonauts demonstrated a conventional pattern of horizontal target acquisition that consisted of three phases. During the first phase, with a 181-240ms latency, an emerging saccade was directed toward the target. This initial saccade was followed 15-40ms later with a head movement towards the target. During this second phase, gaze reached the target with a joint eye and head movement and the saccadic movement was STEM Today Page 18

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completed. During the third phase, the head was still moving toward the target, with a compensatory movement of the eyes approximately equal to that of the head permitting gaze stabilization to occur (Fig. 1).

In spite of this relatively common pattern of gaze stabilization, the variability of the major parameters (peak head, eye velocity and amplitude) was extremely mutable. That is, while there is a common pattern of acquiring

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specific targets with the head and eye free to move from straight ahead gaze to a new peripheral target; it is believed that trade-offs in head and eye velocities and peak amplitudes can be selectively varied according to a preferred strategy. A simple cluster analysis that involved partitioning the data into related subsets according to flight crew assignment showed two distinct groups (pilot and non-pilot) where unique head and eye movement strategies were used for target acquisition (Table 1).

Specifically, non-pilots employed what was termed a Type-I strategy consisting of high velocity head movements with large peak amplitudes, while pilots used primarily low velocity, small amplitude head movements (Type-II) to acquire the targets (p < 0.02).

Fig. 1 shows the analog responses recorded for both Types-I and -II strategies before flight and immediately (2 + days) postflight. For both strategies peak head velocities increased as the angular distance to the target increased (p < 0.01) resulting in greater discrimination between the two distinct strategies for the 60â&#x2014;Ś targets (Fig. 2). These differences in peak head velocities were also reflected in the time it took to stabilize gaze.

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These data suggest that extended exposure to long duration microgravity affected the target acquisition process substantially. After landing we observed changes in both the amplitude and kinematic parameters for the head and eye movements related to the Type-I and -II strategies. As seen in Fig. 2, and consistent with the newly adopted strategy, during the early stage of recovery after space flight (R+1/+3) peak head velocities for the Type-I group significantly decreased when compared to the preflight values for the 30◦ and 60◦ targets (p < 0.02) (Fig. 2-A). Changes in head velocity for the Type-II group showed an increase that was also expressed primarily for the 30◦ and 60◦ targets (p < 0.02) (Fig. 2B). When peak head amplitude was examined there was not a significant difference in the 20◦ and 30◦ target compared to preflight.

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At the same time peak head amplitudes did not change significantly in response to the 20◦ , 30◦ or 60◦ targets (primarily because of the variability across trials) but did show a trend towards significance when acquiring the 60◦ target (Fig. 3).

In the Type-I strategy group, postflight testing showed a significant decrease in eye velocity compared with preflight performance (p < 0.02) for all target locations (Fig. 4A). These changes were largest in response to 60◦ targets. Saccades showed a slight tendency to decrease in amplitude while saccade duration remained fairly constant. For the Type-II group (Fig. 4B) the decrease in peak eye velocity decrease was smaller than that for the Type-I group, but was significant for only the 20◦ targets (p < 0.05). It is interesting to note that while peak eye velocity decreased for all target displacements for both the Type-I and II strategy groups, the pattern of the decrease has a tendency to be somewhat opposite in nature for the two groups. That is, postflight peak eye velocity for the Type-I strategy has a tendency to decrease from the 20◦ target to the 60◦ target, while for the Type-II strategy, postflight eye velocity tends to increase from the 20◦ to 60◦ target. At the same time saccade amplitudes for both groups showed a non-significant tendency to decrease across all target displacements.

On R+1, latency measurements for the eye and head movements to the 60◦ target increased on averaged by 25-40ms with the exception of the TypeI group in which the head latencies in response to the 60◦ targets increased by 100ms (Fig. 5). A gradual return to baseline values was observed by R+8.

Preflight, it took each cosmonaut 450-640ms to stabilize their gaze after the presentation of the target.

This time (gaze latency) increased as a function of the angular position of the target (Fig. 6). On the initial days of recovery all cosmonauts took longer for gaze stabilization to occur. For example, on R+1/2 gaze latencies exceeded the cosmonaut’s preflight baseline values by 110-10 ms. These changes were more characteristic of the Type-I strategy for all the target distances. This difference gradually diminished, and by R+8 gaze latencies for the Type I group approached that of the baseline values.

The observation that a particular strategy in acquiring targets was adopted by some cosmonauts, but not all, contributed to the variability in our data samples. Further analysis combining all responses by both groups (Types-I and -II) across all target displacements revealed an interesting pattern of statistical variation related to the different parameters associated with the acquisition of the targets used in this investigation. Specifically, after space flight, the spread in values for eye latency reached 42.6% (vs. 6.67% before flight), and head latency had a value of 37.5% (vs. 14.22% before flight). The range of variation for gaze latency was also increased following flight during the first week to 34.3% (vs. 15.78% before flight). For the head and eye peak amplitudes, the variability decreased after space flight to 24.1% (vs. 44.1% from preflight) for the head and 17.6% (vs.

30.1% preflight) for the eye.

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Neurological, Sensorimotor, and Sensory difference between Men and Women during and after Spaceflight

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Dr. Millard F. Reschke has explored the specific differences in Neurological, Sensorimotor, and Sensory responses between men and women during and after spaceflight[Reschke et.al.].

Specific Neurological and Sensory Differences Memory processing

Studies consistently indicate a preferential involvement of the left amygdala in memory for emotional material (generally visual images) in women, but a preferential involvement of the right amygdala in memory for the same material in males. This laterality, "women left, men right," mirrors what is seen at rest, indicating that the response to emotional stimulation stems from a baseline that is already differentially "tilted"â&#x20AC;&#x2122; between the sexes.

Neuronal cell death Neuronal cell death pathways differ between men and women. Female neurons more often die through classical, caspase-dependent apoptosis, while male cells die more often through caspase-independent, apoptosis initiating factor-mediated cell death. This finding could potentially be important in developing treatment for neurodegenerative disorders or injuries following stroke Opioid receptor binding Several brain regions show significantly different levels of opioid receptor binding in men versus women, including the amygdala and thalamus. These differences can lead to sex differences in response to pain analgesics.

Vision processing Men have significantly greater sensitivity for fine detail and for rapidly moving stimuli, while women exhibit better color discrimination, in part because many males suffer from color blindness, an X-chromosome related genetically inherited disorder.

Somatosensation Relatively little information is available on sex differences associated with tactile sensation, but some differences are known. On average, women are more sensitive than men, over the entire body, to touch and pressure.

Women appear to be more sensitive to temperature differences while men score better than females on a variety of haptic tasks (object or position recognition involving touch and proprioception). Reporting of pain and pain sensation is rife with many biases (social, gender, ethnicity, culture, etc.), but on average, women do appear to show a greater sensitivity to pain than men-probably due to biological mechanisms, as well as psychological and psychosocial factors.

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Vestibular system Gross anatomy Women have fewer total myelinated axons in the vestibular nerve than men, which may help explain the female bias (that has been verified via epidemiological studies) of developing many vestibular disorders, such as vertigo. In men, the otoliths, utricle, saccule, and superior semicircular canals are significantly larger than in women.

Vestibular nucleus and hormones In rats, some evidence suggests that the estrus (menstrual) cycle may influence the medial vestibular nucleus synaptic transmission and plasticity plasticity, with the levels of circulating 17β estradiol being the main factor in these differences.

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Spatial task performance Sex differences have been found in circular vection (orientation within a spinning environment), field dependence (perceiving orientation based only on visual cues), perception of veridical vertical with body tilt (correctly identifying the true vertical to the ground when the body is tilted), and perception of the morphological horizon. These differences have been partially assigned to biological differences in the vestibular system, including the difference in otolith size, but some evidence suggests that cognitive training regarding attention to cues can decrease these sex differences.

Motion Sickness-laboratory testing A commonly held belief is that females are more susceptible to motion sickness than males. Both social and research design have probably contributed to this bias. Research conducted in the NASA Johnson Space Centerâ&#x20AC;&#x2122;s Neurosciences Laboratory has subjected over 200 subjects to a variety of motion sickness tests (coriolis sickness susceptibility [CSSI], sudden stop, offvertical rotation, parabolic flight, etc.). No difference was found in susceptibility between men and women nor did testing during any phase of the menstrual cycle for females have an effect. Responses to particular tests were variable. For example, some individuals became nauseous during a CSSI test but not during the off-vertical axis rotation test.

Motion Sickness: spaceflight The incidence of motion sickness obtained from post-flight debriefs of long-duration International Space Station, or "space station," (32 male, 10 female) and short-duration Space Shuttle (564 male, 100 female) astronauts show that, on average, female crewmembers that flew on both the space station and shuttle reported both space motion sickness and entry motion sickness (EMS) symptoms more frequently than male crewmembers (these data were mined from the NASA Lifetime Surveillance of Astronaut Health [LSAH] database). The one exception is that men who were crew members on the space station reported a higher incidence of EMS than women after returning from a long-duration spaceflight.

Postural Ataxia: spaceflight On average, female crewmembers who flew on both the space station and space shuttle reported post-flight vestibular instability symptoms (feeling abnormally heavy, clumsiness, vertigo, persisting sensation after-effects, or having difficulty walking a straight line) more frequently than male crewmembers (these data were also mined from the LSAH database). All responses were subjective and were reported to a flight surgeon as part of a standard post-flight medical debrief. The debrief did not always specify the symptoms. In a study of computerized dynamic posturography before and after long-duration bed rest, analyses of sensory organization test scores suggest no differences between men and women.

Hearing/Auditory function Numerous epidemiological studies have been conducted to compare differences in hearing sensitivity among men and women, confirming that hearing sensitivity declines with age, even in populations screened for a history of noise exposure. These studies have also shown that hearing sensitivity (when reported by conventional pure-tone audiometry) declines faster in men than in women at most ages and in most frequencies tested. The most recent National Health and Nutrition Examination Survey28 revealed that the odds of such hearing loss were 5.5-fold higher in men than in women.

Even when studies carefully screen for ear disease and noise exposures, however, hearing levels and longitudinal patterns of hearing change are highly variable. This variability has been attributed to smoking, genetic factors, and cardiovascular risks. Hearing sensitivity is particularly vulnerable to hazardous noise exposures (e.g., in industrial, military, and recreational environments), but sex differences in age-associated hearing loss occur even among populations with relatively low-noise occupations and with no evidence of noise-induced hearing loss.

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In addition to pure-tone audiometry, distortion product otoacoustic emissions (DPOAEs) have also been used to assess peripheral hearing status. DPOAEs are believed to reveal subtle cochlear changes that may be overlooked by audiometry. Studies show that aging males experience greater decreases in DPOAEs amplitudes compared to aging females. This decrease in DPOAEs is often proportional to the degree of hearing loss.

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NASA conducts a unique hearing-monitoring program, in which crewmembers undergo audiometric testing at least once per year during their active astronaut career (and even more frequently when assigned to space missions). Later, when participating in NASAâ&#x20AC;&#x2122;s LSAH program, former astronauts may continue to have their hearing tested for the rest of their lives. This database offers the opportunity to compare longitudinal differences in hearing sensitivity seen in male and female astronauts over asmuch as a 5-decade span of life (Fig. 1).

When comparing high-frequency hearing sensitivity, the LSAH databaseâ&#x20AC;&#x2122;s female population has better hearing thresholds than men at every epoch of life, starting in their mid-30s, approximately the age when most astronauts begin their careers. Female astronauts show no significant differences in hearing thresholds between ears except in those older than 55 (though the sample size for this population is rather small at that age), when the left ear thresholds are slightly better than those in the right ear. Male astronauts show greater hearing loss in the left ear than in the right ear at every age; this finding is consistent with many demographic studies, particularly those in which right-handed subjects have shot shoulder-fired weapons (exposing the left ear to most of the blast wave from the weaponâ&#x20AC;&#x2122;s muzzle). The vocational and avocational activities of many astronauts, military and nonmilitary, often include such firearms. An important finding from this database (unpublished data) is that although males and females show the expected age-related differences in hearing loss, spaceflight does not seem to affect men and women differently.

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Distance and Size Perception in Astronauts during Long-Duration Spaceflight

The objective of this experiment was to investigate whether an alteration in cognitive visual-spatial processing, such as the perception of distance and size of objects, is also taking place during prolonged exposure to microgravity. Eight astronauts (one woman, seven men) ranging from 45 to 56 years (M = 49.4, SD = 3.9) were tested before, during, and after a long-duration mission on board the ISS. Mission durations ranged from 57 to 195 days (M = 154.4, SD = 43.3). Subjects were all tested three times pre-flight (at approximately L-90, L-60, and L-30 days), four times in-flight (FD) and three times post-flight (at R+0 or R+1, R+4, and R+8 days).

Additionally, a control population of 91 participants (34 women, 57 men) was tested in normal gravity (1G) on the ground. The average age of participants was 43.2 years (SD = 10.9).

Results Cube Size Perception When comparing the dimensions of the cube that the subjects had adjusted so that it looked normal to them, STEM Today Page 25

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authors found no significant difference between the data collected with the astronauts at L-90 days and with the 91 control participants (Figure 1). In addition there was no difference between the data collected with the astronauts across pre-flight sessions at L-90, L-60, and L-30 days. There was a clear trend for the height of the cube to be smaller and its depth to be larger in-flight compared to pre-flight.

A Wilcoxon signed-ranks test for paired differences indicated that the difference in height between the flight day period FD65-120 and the final pre-flight data collection session (L-30) was significantly different from zero (Z = 4.24, p < 0.001, r = 1.5). A significant difference was also observed between the period FD133-192 and L-30 (Z = 3.12, p < 0.001, r = 1.1). The difference in depth between the period FD133-192 and L-30 was also significantly different from zero (Z = 3.92, p < 0.001, r = 1.39).

Cube Hand Drawing There was no difference in the length of the horizontal, vertical, or oblique lines of the Necker cube drawings between the pre-flight L-90, L-60 and L-30 sessions. During the flight, the data is consistent with the cube size perception data although the effects are not as large. A Wilcoxon signed-ranks test for paired differences indicated that the length of the vertical lines was significantly smaller during the periods FD65-120 (Z = 1.69, p < STEM Today Page 26

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0.04, r = 0.6) relative to L-30 (Figure 2). All other paired differences were not significant.

Distance Perception with Cubes In this test, subjects were asked to estimate the perceived distance of a cube by replicating the extent they were viewing in another direction through visual matching. The true distances ranged between approximately 30 and 60 cm. The perceived distances were fairly accurate on Earth in both the astronauts and the control participants (Figure 3). In orbit, the astronauts underestimated the distance, as consistently shown when adjusting the distance of the cube either along the horizontal frontal or sagittal direction. However, this underestimation was not found to be significant, presumably due to the larger variance in the data for this test, for both the ground-based controls and the astronaut sample.

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Distance Perception with Natural Scenes Because of the time constraints, only 12 photographs were used: six for testing horizontal distance and six for testing vertical distances. Prior to the flight, the egocentric distances reported by the astronauts ranged from 2 m to 2000 m, with a uniform distribution. All pre-flight measures were not significantly different from each other or from post-flight measures. In addition, these distance estimates were not significantly different from those reported by the 91 participants in the control group. On average, the astronauts reported distances above 50 m to be about 20%-25% smaller in-flight than pre-flight (Figure 4). Wilcoxon tests indicated that this underestimation was significant for distances that were reported to be at 180 m (Z = 1.74, p < 0.04, r = 0.62) and 1500 m (Z = 1.82, p < 0.03, r = 0.64).

The judgment of the size and distance of objects is altered in astronauts following several months in orbit.

Visual perception of the height and the depth of objects, as well as the distances of objects are particularly affected. Although our sample of astronaut-subjects is small and only a few differences between pre-flight and in-flight measurements are significant at p < 0.05 level, there is a consistent trend in our results that warrants reporting. Our findings suggest that the mental representation of the three-dimensional world changes during spaceflight. This change in scale and shape of astronautsâ&#x20AC;&#x2122; visual space may have implications for future human exploration missions.

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When astronauts adjusted the size of a cube so that it looked normal in orbit, they made its height shorter and its depth longer than on Earth, which means that a perfect cube was perceived as taller and shallower.

We also found the same features in the hand drawing of cubes: the height of hand drawn cubes was shorter in-flight compared to pre-flight. These results indicate that both cognitive and perceptual-motor changes take place during adaptation to spaceflight. The two distance perception tests also indicate that astronauts tend to underestimate the distances of objects located either at very close range (<60 cm) or at long-range (180 m and 1500 m) compared to Earth measurements. Given previous findings that in a terrestrial environment large distances are underestimated by about 10% , our results suggest that in orbit the underestimation of true distances in orbit could be as high as 35%.

The increase in perceived height of the cube and the underestimation of its distance are inconsistent with the visual size constancy rule, which predicts that we tend to attribute a smaller size to an object when we underestimate its distance. The perceived depth of the cube, however, decreases in orbit. According to the sizeconstancy rule, if a 2D object keeps the same aspect (it varies in a homothetic manner) when it moves closer or farther away, a 3D object does not. The 3D shape changes with distance according to perspective. The frontal elements decrease as an inverse function of distance, whereas the depth decreases as an inverse function of the square of the distance. Accordingly, perceived depth should be less affected by distance than perceived height.

Indeed, in the hand drawn cubes, a significant effect on depth was not observed.

Distortions of the visual space and misperception of object size, distance, and shape during space missions represent potentially serious operational consequences. For example, if a crewmember does not accurately gauge the distance of a target, such as a docking port or an approaching vehicle then the speed of this target may be misevaluated, leading to operational errors. In fact, it is believed that a poor sense of closing speed was a contributing cause to the collision between a Progress supply spacecraft with the Mir space station in 1997.

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References Andreano JM, Dickerson BC, Barrett LF. Sex differences in the persistence of the amygdala response to negative material. Social Cognitive and Affective Neuroscience. 2014;9(9):1388-1394. doi:10.1093/scan/nst127.

Hamann S. Sex differences in the responses of the human amygdala. Neuroscientist. 2005 Aug;11(4):288-93.

Review. PubMed PMID: 16061516.

Reschke MF, Cohen HS, Cerisano JM, et al. Effects of Sex and Gender on Adaptation to Space: Neurosensory Systems. Journal of Women’s Health. 2014;23(11):959-962. doi:10.1089/jwh.2014.4908.

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Millard F. Reschke, Ognyan I. Kolev & Gilles Clément , Eye-Head Coordination in 31 Space Shuttle Astronauts during Visual Target Acquisition , Scientific Reports 7, Article number: 14283 (2017) doi:10.1038/s41598017-14752-8 .

Jason T. Richards, Jonathan B. Clark, Charles M. Oman, Thomas H. Marshburn, Neurovestibular Effects of Long-Duration Spaceflight: A Summary of Mir-Phase 1 Experiences.

Available on NASA Website (https://ntrs.nasa.gov/search.jsp?R=20100033747).

Millard F. Reschke, PhD, Edward F. Good, MD, Gilles R. Clément, PhD , Neurovestibular Symptoms in Astronauts Immediately after Space Shuttle and International Space Station Missions, Volume: 1 issue: 4, Article first published online: October 23, 2017; Issue published: December 1, 2017, https://doi.org/10.1177/ 2473974X17738767.

Don Pettit, Mars Landing on Earth: An Astronaut’s Perspective , Journal of Cosmology, 2010, Vol 12, 35293536.

Elena S. Tomilovskaya, Millard F. Reschke, Jody M. Krnavek, Inessa Kozlovskayaa , Effects of long-duration space flight on target acquisition , Acta Astronautica, Volume 68, Issues 9-10, May-June 2011, Pages 14541461, https://doi.org/10.1016/j.actaastro.2009.11.005 .

Clément G, Skinner A, Lathan C. Distance and Size Perception in Astronauts during Long-Duration Spaceflight. Life (Basel). 2013 Dec 13;3(4):524-37. doi: 10.3390/life3040524. PubMed PMID: 25369884; PubMed Central PMCID: PMC4187133.

Oberg, J.E. Shuttle-Mir’s lessons for the international space station. IEEE Spectr. 1998, 35, 28-37.

Siki, R.; Simecek, M. The effect of confinement on visual space perception: The results of Mars-500 experiment. Atten. Percept. Psychophys. 2013, in press.

Linkenauger, S.; Witt, J.K.; Stefanucci, J.K.; Bakdash, J.Z.; Proffitt, D.R. The effects of handedness and reachability on perceived distance. J. Exp. Psychol. 2009, 35, 1649-1660.