Health - Spaced out: Clearing astronauts' mental fog

 

(Image: NASA/Science Photo Library)

Being in space messes with your brain – bad news if you're steering a spacecraft. How can we save astronauts from the space stupids

JUNE 1997. About 350 kilometres above Earth, the Russian Progress resupply vehicle begins closing in on the Mir space station. But Mir's range-finding radar begins malfunctioning. With only the on-board camera, handheld range finders and their eyes, Mir's cosmonauts struggle to see the approaching vehicle.

To get a better view, they begin moving between the station's modules. Yet they start to feel disoriented. When the cosmonauts finally spot Progress, it is too close and moving too fast. The supply vehicle smashes into Mir, rips apart a solar panel, punches a hole in one of the modules and decompresses the station.

What happened? According to Charles Oman at the Massachusetts Institute of Technology's Man Vehicle Laboratory, this may have been a classic case of the mental befuddlement caused by space travel. Symptoms include mental dullness, strange visual illusions, spatial disorientation, and even an apparent dissociation between the body and the brain's sense of self.

Thankfully, no one was killed in the Mir crash, but these problems can only become more dangerous as we prepare for ever-longer spaceflights. "It was a serious incident," says Oman. "It threatened the lives of the crew members on board and the integrity of the space station."

Reports of "space stupids" or "space fog", as the feeling of confusion is sometimes known, have been documented for at least two decades. "These are highly trained, highly motivated professionals, so any time they suggest that there might be a change in their cognition, you have to take them seriously," says David Dinges, who studies the effects of zero gravity on neuro-behaviour at the University of Pennsylvania in Philadelphia.

Terrestrial simulations of spaceflight, such as the Mars 500 project in Moscow, Russia, can study the psychological stresses of prolonged isolation during a space mission, but they do little to investigate other mind-bending effects of space travel. For this reason, many researchers are taking to the sky, using aeroplane flights specially designed to produce moments of weightlessness to study the effect of the absence of gravity on our brains. Together with observations from the actual space flights, this work aims to find ways to alleviate the symptoms of space fog and hopefully avoid disaster.

Of course, some of the confusion will simply be down to the physical and mental stresses of space travel. From the moment of lift-off, an astronaut's body is bombarded with various uncomfortable sensations - the roar of the rocket engine, sinus congestion and flashes as cosmic rays hit their retinas, to name a few. Then there are the challenges of functioning at full efficiency in an alien environment when faced with disturbed sleep cycles and high levels of carbon dioxide.

While there's no doubt that all these factors can cloud an astronaut's mind, could the absence of gravity itself be behind some aspects of the mental malaise? On Earth, we are able to balance ourselves thanks to the vestibular system, a collection of sensory structures in the inner ear that are highly sensitive to gravity's pull. Its nerves send signals to the eyes and muscles, but also connect to a surprising number of brain regions, including areas crucial to human cognition, like the parietal cortex. "Why would [vestibular circuits] be there on the cortical surface if they had no function?" asks Fred Mast of the University of Bern in Switzerland.

Messing with the vestibular system certainly seems to affect the judgement of Earth-bound individuals. For instance, Mast and colleagues have found that tilting people's bodies by 135 degrees disrupts their ability to recognise faces, to the point that they can no longer detect strange distortions in images (Perception, vol 36, p 537). Other experiments have found that disrupting a person's balance by stimulating nerves in the inner ear can play havoc with their memory and their ability to imagine a scene from different vantage points (Experimental Brain Research, in press, DOI: 10.1007/s00221-011-2929-z).

If an impaired sense of balance has this effect on Earth, what might happen in space? Two decades ago, Gilles Clément of the National Centre for Scientific Research (CNRS) in Toulouse, France, and colleagues asked astronauts to close their eyes and write their name horizontally and vertically, both before a space flight and in zero gravity. They found that the size of the written letters decreased in space, particularly in the vertical direction, and the change was greatest during the first three days of a mission. Later, during the late 1990s, the researchers asked two astronauts aboard the shuttle Discovery to sketch line drawings of cubes, again with their eyes closed. The horizontal lines tended to be longer than the vertical ones when the astronauts were in space. The team concluded that the absence of gravity influences the way the brain perceives the vertical dimension (Neuroscience Letters, vol 295, p 37).

More recently, Clément's team examined a visual illusion known as Mach's square-diamond ambiguity, in which a line drawing appears to be a diamond when you stand upright and a square when you tilt your head This shows that our visual system determines an object's shape based on its orientation relative to the downward pull of gravity. But what if there is no obvious up or down?

To create the conditions of low gravity without the cost of space travel, the researchers used parabolic flight, in which an aircraft first accelerates upwards - creating forces of about 1.8 g - and then free-falls for about 20 seconds, during which the passengers experience near weightlessness. In such conditions, people were far more likely to see the shape as a diamond, again suggesting that gravity - or rather its absence - can influence the way the brain interprets the raw images captured by our eyes (Neuroscience Letters, vol 447, p 179).

Low gravity could even change an astronaut's ability to form mental images. During parabolic flights, Mast and Luzia Grabherr, also at the University of Bern, showed their subjects various drawings of a body with an outstretched arm, or a hand with fingers splayed. They were asked to decide whether the arm or hand was from the left or right side, which involves mentally rotating the images. On Earth, the task is easy, but in microgravity it took significantly longer to do (Journal of Vestibular Research, vol 17, p 279).

Crucially, the volunteers showed no impairment when it came to mental rotations that involved abstract objects rather than body parts. "That definitely gives us a clue that [weightlessness] has an effect on some cognitive functions and not others," says Mast.

Through the looking glass

It is not hard to imagine how these effects could take a toll during a space mission, when astronauts need a high degree of visual and spatial awareness to carry out tasks such as piloting a vehicle or driving a rover. For example, crew members of the Apollo missions have reported that when driving lunar rovers, they often misperceived the slopes of terrains and at times felt that the vehicles were overturning when bouncing off craters, causing them to slow down (Journal of Gravitational Physiology, vol 15, p 7).

Worse still, microgravity can induce disorientating illusions that might completely throw an astronaut's judgement. One shuttle pilot reported that having just woken up and removed the shades on the cockpit windows, he found the Earth wasn't where it had been when he went to sleep. This triggered what is called a visual reorientation illusion (VRI), in which the astronaut feels that the surrounding surfaces have flipped - floor becomes ceiling, left becomes right. "You feel a little bit like Alice slipping through the looking glass," says Oman. The shuttle pilot, feeling extremely disorientated, threw up. Besides the physical discomfort, this feeling could lead to serious mistakes, adds Oman. "You are more likely to throw a switch the wrong way, or reach the wrong way for remembered objects."

Other astronauts have reported a related phenomenon known as the inversion illusion, in which they feel that they are upside down. That's subtly different to VRI - in which the astronaut feels that the surroundings have changed, while the body remains upright.

What could be causing these strange phenomena? In the absence of input from the vestibular system, the brain has to rely on visual cues to tell what's up and what's down. When these cues are ambiguous, or seem to change abruptly, the brain reconsiders its position in relation to its surroundings - and the astronaut undergoes the visual reorientation illusion.

The inversion illusion is more mysterious, since the feeling of being upside down persists even with your eyes closed. Oman speculates that it might be a side-effect of a physiological change that occurs when humans enter zero gravity. When there is no pull of gravity on the body's fluid column, fluid moves from the lower extremities to the torso and head, giving astronauts puffy faces, bulging eyes and spindly legs - changes that the brain might associate with being upside down.

There could be a more exotic explanation, says Isabelle Viaud-Delmon of the National Centre for Scientific Research (CNRS), in Paris, France. She thinks inversion illusions are related to out-of-body experiences (OBEs) and the room-tilt illusion, a condition in which people on Earth suddenly feel their visual field rotate 90 degrees or completely turn upside down. These phenomena are known to be caused by an error in the processing of the brain's temporoparietal junction (TPJ), which integrates vestibular inputs with visual information and signals from our joints, tendons and muscles.

Viaud-Delmon suspects that zero gravity might cause a similar disruption to the TPJ's processing - making you more susceptible to OBEs and related phenomena, she says. To test her hypothesis, she is conducting an in-flight variation of the well-known body illusions, in which researchers confound the brain's sensory circuits to persuade subjects that they are embodying a rubber doll, or a virtual body a few metres in front of the person's actual location. The experiment is on-going, but she thinks she can guess the outcome. "I have tried it on a parabolic flight, and it's quite powerful," she says, of her own in-flight OBE.

While figuring out the source of these strange illusions will satisfy scientific curiosity, for astronauts the important thing is to reduce the risks of accidents caused by space fog. There are a few possible solutions so far. For example, a simple life jacket fitted with an airbag could help them stay oriented. When inflated, the airbag put mechanical pressure on the chest, which seemed to help volunteers on a parabolic flight more effectively judge their orientation, according to Clément's team (Neuroscience Letters, vol 413, p 150).

Dinges has developed an early warning system to tell whether astronauts' cognitive abilities might be failing. His psychomotor vigilance test monitors their reaction times, which should be sensitive to and help indicate the mental confusion associated with space fog. The system is now installed on all the support computers on the International Space Station (ISS), and Dinges is halfway through collecting data from ISS astronauts.

One thing the results may show is whether astronauts' cognitive ability declines the longer they are in space, or if they eventually adapt to zero gravity and regain their abilities. While the latter might seem like good news, it's not necessarily so for missions to Mars. If an astronaut gets acclimatised to zero gravity during the flight, they face an immediate challenge upon arriving at the Red Planet, which has 3/8ths of Earth's gravity. No one knows what the sharp transition will do to an astronaut's ability to steer and land a vehicle.

There's some evidence that it won't be easy. The Bodies in Space Environment (BISE) project, a collaboration between NASA astronauts on the ISS and researchers from York University in Toronto, Canada, has shown that an astronaut's ability to tell up from down is damaged by extended periods of weightlessness, and these effects linger even six months after return to Earth. The results, presented at the Eighth Symposium on Vestibular Research in April 2011 at Houston, Texas, suggest that astronauts landing on Mars might face similar difficulties.

One possible solution for missions to Mars would be to spin astronauts in centrifuges during their trip. This would create artificial gravity, helping them adapt to conditions when they land. The entire spacecraft could even rotate, as in the movie 2001: A Space Odyssey, though this kind of technology is some way off.

A fanciful solution, perhaps - but one that may become increasingly likely as we discover more and more about the mind-bending effects of zero gravity. As the Mir cosmonauts know, space fog can strike at crucial moments. Luck offset disaster in that accident - but it would be foolish to rely on it a second time.

Nav for Moonwalks

Spatial disorientation could be especially problematic for astronauts on long space walks during future moon and Mars missions. Apollo 14 astronauts who walked 2 kilometres on the moon became so disorientated that they failed to reach their goal, the Cone crater, before running out of resources. Low gravity - which can impair the brain's visuo-spatial skills - may have been partly to blame.
To help, Charles Oman and colleagues at the Man Vehicle Laboratory at MIT have developed the Lunar Astronaut Spatial Orientation and Information System (LASOIS), which will combine information from cameras and altimeters on lunar orbiters with further input from sensors on the astronaut. This includes a pair of cameras on the chest, devices in the boot to monitor the movement of the astronaut's feet, and a helmet-mounted camera to track stars. The integrated information, presented on a wrist display, will help the astronaut navigate.
The system was tested over a 4.8-kilometre route in lunar-like environments in Moses Lake, Washington, and Black Point, Arizona, and enabled its users to reach a position only 200 metres from the set end point. The results were presented at 2011's Lunar and Planetary Science Conference last March at The Woodlands, Texas.

Anil Ananthaswamy is a New Scientist consultant

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