Already in ancient Greece, philosophers declared that our senses deceive us. They pointed to the refraction of objects in water and distortion of dimensions when removed, insisting that only the mind can show the truth. We call distorted perception an illusion, although for the most part this "deception" does not prevent us from building a picture of the world.
In space, ordinary earthly illusions acquire new properties. All these effects are caused by the reaction of the human body to the absence of gravity.
The perception of space is regulated by the vestibular apparatus - an organ that senses changes in the position of the head and body in space, as well as the direction of movement of the body. It is located in the inner ear and is a complex of cell clumps and calcareous formations.
The vestibular apparatus consists of semicircular canals and a statolith apparatus. In the area of the latter, there are sensitive hair cells immersed in the otolithic membrane, a gelatinous substance. It contains ear stones (otoliths) - formations, the pressure of which on different parts of the membrane depends on the position of the body in space. But when a person finds himself in zero gravity, these stones do not exert pressure. Therefore, deprived of a natural way of orientation in space, astronauts begin to experience various illusions.
Diagram of the structure of the otolith membrane / Illustration by RIA Novosti. A. Polyanina
In order to study “space illusions”, a large-scale experiment was carried out at the Institute of Biomedical Problems of the Russian Academy of Sciences, during which the pre- and post-flight state of the cosmonaut's body was studied, and everything that happened to him on the ISS (International Space Station) in zero gravity was recorded. It turned out that in this unusual state for the human body, orientational, kinetic, coordinate, propriocetive illusions are manifested.
Astronauts aboard the International Space Station / NASA
Orientational illusions were observed in almost all cosmonauts (98%), gradually decreasing over several hours or even minutes. They were expressed in the loss of space perception. If we inspect the room, and then close our eyes and try to touch the wall or some object, then, most likely, we will make a small mistake, but in general we will be able to correctly estimate the distance to the object and the direction of movement. On the ISS, even after studying the surrounding space, when the lights were turned off, sometimes complete disorientation arose - a person could not determine in which direction and for how long to move to the target.
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Kinetic deception was characterized by the feeling of rotation of one's own body around, as well as movement along an axis. At first glance, kinetic illusions seem to be a fun attraction, but it is impossible to finish such a “ride” on your own. Such illusions turned into coordinate ones: it seemed to people that their body was tilted to the left or right, backward or forward, and sometimes it was upside down.
Zero gravity can literally make a person feel like the floor is slipping from under his feet and the walls are falling. Some cosmonauts also noted the illusory sensation of the position of various parts of the body: “it seems that you are sitting bent over, but in fact you are lying flat in a sleeping bag”, “your hands are on top, but it seems that they are below” - this is how propriocetive illusions manifested themselves.
This is how the artist envisions the effect of a “ falling ceiling ” in a state of propriocetivny illusions / Fotolia / tiero
Along with illusory reactions, 72% of cosmonauts had difficulties in tracking a moving target and fixing their gaze on it, and discoordination manifestations were also noted - mistakes when trying to grab an object, banging their heads on a panel while “swimming” inside the station. Analysis using electrooculography and mathematical methods revealed a connection between the development of orientational illusions and the detected disorders of oculomotor reactions.
“We conduct pre- and post-flight examinations of all crew members in order to understand at what levels the central nervous system changes,” explains Georgy Yekimovsky, senior researcher at the Vestibular Physiology Laboratory of the Institute of Biomedical Problems of the Russian Academy of Sciences. - We use several methods to study how severe vestibular disorders are, including those developed by our laboratory. The complex includes electrooculography with a special set of tests and unique software developed for cosmonauts at our institute. We also use the method of video photography, that is, we support neurosensory connections between the visual activity of the eye, the state of the vestibular and nervous systems of the body as a whole."
Changing the trajectory of eye movement when tracking an object / Illustration by RIA Novosti. A. Polyanina
The electrooculography method is based on recording the potential difference that occurs when the eyeball moves. The eye itself is a dipole in which the cornea is generally electropositive to the retina. To register potentials, electrodes are placed crosswise around the eye. If the eyeball is at rest, then the electrodes are at equal distances from the positive and negative poles. If the patient looks to the side, then one of the electrodes moves closer to the positive pole, and the other to the negative. As a result, the latter becomes electronegative, and the former becomes electropositive. The direction of the eye movement can be established from the potential sign.
Recording of spontaneous eye movement / Illustration by RIA Novosti. A. Polyanina
Georgy Yekimovsky reports: “If illusions arise only during the first three days, this is called adaptation, but if they continue after a given time, we can talk about the occurrence of space motion sickness. This is the name of a condition in which certain symptoms or syndrome (a set of symptoms) are added to the disturbance in the perception of space, disrupting the astronaut's work activity in zero gravity. After returning to Earth, sometimes the astronauts also have illusions similar to the "cosmic" ones. One of the curious post-flight effects was that some astronauts experienced the movement of the Earth for several days after landing. They physically 'felt' the planet rushing through space."
Studying the response of astronauts to weightlessness helps to treat imbalance and dizziness in ordinary people. There are two treatment options. The first method contains pharmacotherapy, and the second consists in carrying out a series of trainings of the vestibular apparatus, similar to those carried out for the preflight training of cosmonauts.
A new experiment, Virtual2, is being prepared at the Institute of Biomedical Problems of the Russian Academy of Sciences to study the reactions of the vestibular apparatus to weightlessness. At the moment, the equipment is being tested on Earth, in conditions simulating zero gravity on the ISS.