Neuroscience in space
   HOME

TheInfoList



OR:

Space neuroscience is the scientific study of the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
(CNS) functions during
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in o ...
.
Living systems Living systems are open self-organizing life forms that interact with their environment. These systems are maintained by flows of information, energy and matter. In the last few decades, some scientists have proposed that a general living syst ...
can integrate the inputs from the
senses A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...
to navigate in their environment and to coordinate
posture Posture or posturing may refer to: Medicine * Human position ** Abnormal posturing, in neurotrauma ** Spinal posture ** List of human positions * Posturography Posturography is the technique used to quantify postural control in upright stance in ...
,
locomotion Locomotion means the act or ability of something to transport or move itself from place to place. Locomotion may refer to: Motion * Motion (physics) * Robot locomotion, of man-made devices By environment * Aquatic locomotion * Flight * Locomo ...
, and
eye movements Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of inte ...
.
Gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
has a fundamental role in controlling these functions. In
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
during spaceflight, integrating the sensory inputs and coordinating motor responses is harder to do because gravity is no longer sensed during
free-fall In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on i ...
. For example, the
otolith An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
organs of the vestibular system no longer signal head tilt relative to gravity when
standing Standing, also referred to as orthostasis, is a position in which the body is held in an ''erect'' ("orthostatic") position and supported only by the feet. Although seemingly static, the body rocks slightly back and forth from the ankle in the s ...
. However, they can still sense head translation during body motion. Ambiguities and changes in how the gravitational input is processed can lead to potential errors in
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
, which affects
spatial orientation In geometry, the orientation, angular position, attitude, bearing, or direction of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it occupies. More specifically, it refers to the imagin ...
and
mental representation A mental representation (or cognitive representation), in philosophy of mind, cognitive psychology, neuroscience, and cognitive science, is a hypothetical internal cognitive symbol that represents external reality, or else a mental process that ...
. Dysfunctions of the vestibular system are common during and immediately after spaceflight, such as space motion sickness in orbit and
balance disorder A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance ...
s after return to Earth. Adaptation to
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
involves not just the
Sensory-motor coupling Sensory-motor coupling is the coupling or integration of the sensory system and motor system. Sensorimotor integration is not a static process. For a given stimulus, there is no one single motor command. "Neural responses at almost every stage of a ...
functions, but some autonomic nervous system functions as well.
Sleep disorders A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are tests ...
and
orthostatic intolerance Orthostatic intolerance (OI) is the development of symptoms when standing upright that are relieved when reclining. There are many types of orthostatic intolerance. OI can be a subcategory of dysautonomia, a disorder of the autonomic nervous sy ...
are also common during and after spaceflight. There is no
hydrostatic pressure Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body " fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imm ...
in a weightless environment. As a result, the redistribution of body fluids toward the upper body causes a decrease in leg volume, which may affect muscle
viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...
and compliance. An increase in
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult ...
may also be responsible for a decrease in near
visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
. In addition, muscle mass and strength both decrease as a result of the reduced loading in
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
. Moreover, approximately 70% of astronauts experience space motion sickness to some degree during the first days. The drugs commonly used to combat motion sickness, such as scopolamine and
promethazine Promethazine is a first-generation antihistamine, antipsychotic, sedative, and antiemetic used to treat allergies, insomnia, and nausea. It may also help with some symptoms associated with the common cold and may also be used for sedating people ...
, have soporific effects. These factors can lead to chronic fatigue. The challenge of integrative
space medicine Space medicine is the practice of medicine on astronauts in outer space whereas astronautical hygiene is the application of science and technology to the prevention or control of exposure to the hazards that may cause astronaut ill health. Both ...
and physiology is to investigate the adaptation of the human body to spaceflight as a whole, and not just as the sum of body parts because all body functions are connected and interact with each other.


History of space neuroscience

To date, only three countries, the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
,
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
, and China, have the capability to launch humans into orbit. However, 520 astronauts from more than thirty different countries have flown in space and many of them have participated in space neuroscience research. The launch of the first living animal in orbit on Sputnik on November 3, 1957 marked the beginning of a rich history of unique scientific and technological achievements in space life sciences that have spanned more than fifty years to date. The first documented space neuroscience experiments were performed during the third human mission on board the Russian
Vostok Vostok refers to east in Russian but may also refer to: Spaceflight * Vostok programme, Soviet human spaceflight project * Vostok (spacecraft), a type of spacecraft built by the Soviet Union * Vostok (rocket family), family of rockets derived from ...
spacecraft. These experiments began after the crew from previous missions complained from
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
and spatial disorientation in
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
. Space neuroscience experiments typically addressed these operational issues until the
Skylab Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations ...
and
Salyut The ''Salyut'' programme (russian: Салют, , meaning "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed ...
space stations were made available for more fundamental research on the effect of gravity on CNS functions. Approximately 400 space neuroscience experiments have been performed from Vostok-3 in August 1962 to the Expedition-15 on board the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ( ...
in October 2007.


Operational aspects

Sensory and sensorimotor disturbances when arriving in low Earth orbit are well documented, the most known of these being space motion sickness (SMS). Individual differences, spacecraft size, and body movements cause SMS symptoms. Typically lasting the first three or four days of weightlessness, symptoms range from
headaches Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...
and fatigue to
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
and
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteri ...
. The consequences vary from simple discomfort to possible incapacitation, creating potential problems during extra-vehicular activity, re-entry, and emergency egress from the spacecraft. The body receives a variety of conflicting signals from the visual, somato-sensory, and vestibular organs in weightlessness. These conflicting inputs are thought to be the primary cause of SMS, but the precise mechanisms of the conflict are not well understood. Medications currently used to alleviate the symptoms produce undesirable side effects. Astronauts must remain alert and vigilant while operating complicated equipment. Therefore, getting enough
sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...
is a crucial factor of mission success. Weightlessness, a confined and isolated environment, and busy schedules coupled with the absence of a regular 24-hour day make
sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...
difficult in space. Astronauts typically average only about six hours of sleep each night. Cumulative sleep loss and sleep disruption could lead to performance errors and accidents that pose significant
risk In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environm ...
to mission success. Sleep and
circadian cycles A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., endogenous) and responds to ...
also temporally modulate a broad range of physiological, hormonal, behavioral, and cognitive functions. Methods to prevent sleep loss, reduce
human error Human error refers to something having been done that was " not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits".Senders, J.W. and Moray, N.P. (1991) Human ...
, and optimize mental and physical performance during long-duration spaceflight are being investigated. Particular concerns include the effect of the space environment on higher-order cognitive processes like decision-making and the impact of changing gravity on mental functions, which will be important if
artificial gravity Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of re ...
is considered as a
countermeasure A countermeasure is a measure or action taken to counter or offset another one. As a general concept, it implies precision and is any technological or tactical solution or system designed to prevent an undesirable outcome in the process. The fi ...
for future interplanetary space missions. It is also necessary to develop human-response measurement technologies to assess the crew's ability to perform flight-management tasks effectively. Simple and reliable behavioral and psycho-physiological response measurement systems are needed to assess mental loading,
stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
, task engagement, and
situation awareness Situational awareness or situation awareness (SA) is the perception of environmental elements and events with respect to time or space, the comprehension of their meaning, and the projection of their future status. An alternative definition is tha ...
during spaceflight.


Sensory functions in space

All living organisms on Earth have the ability to sense and respond to changes in their internal and external environment. Organisms, including humans, must accurately sense before they can react, thus ensuring
survival Survival, or the act of surviving, is the propensity of something to continue existing, particularly when this is done despite conditions that might kill or destroy it. The concept can be applied to humans and other living things (or, hypotheti ...
. The body senses the environment by specialized sensory organs. The CNS utilizes these sensations in order to coordinate and organize muscle activities, shift from uncomfortable positions, and adjust
balance Balance or balancing may refer to: Common meanings * Balance (ability) in biomechanics * Balance (accounting) * Balance or weighing scale * Balance as in equality or equilibrium Arts and entertainment Film * ''Balance'' (1983 film), a Bulgaria ...
properly. In common speech, five different
senses A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...
are usually recognized:
vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...
,
hearing Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is audit ...
, smell,
taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
, and
touch In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch ( haptic perception), as well as temperature ( thermoception), body position (proprioception), and pain. It ...
. All these senses are somewhat affected by weightlessness. In fact, the human body has seven sensory systems – not five. The sixth and seventh systems are the senses of motion located in the inner ear. The former signals the beginning and end of rotation and the latter signals body tilt relative to gravity as well as body translation. The seventh system no longer provides tilt information in weightlessness; however, it does continue to signal translation, so the afferent signals to the CNS are confusing. The experience of living and working in space alters the way the CNS interprets the otolith organ signals during
linear acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by th ...
. Although the perception is fairly accurate when subjects are exposed to angular acceleration in yaw in-flight, there are disturbances during angular rotation in pitch and
roll Roll or Rolls may refer to: Movement about the longitudinal axis * Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis ** Roll (aviation) ...
, and during linear acceleration along the body transversal and longitudinal axes. Perception of body motion is also altered during the same motion immediately after landing. There is an adaptation to weightlessness in orbit that carries over to post-flight reactions to linear acceleration.


Posture, movement, and locomotions

Exposure to weightlessness causes changes to the signals from the receptors to
touch In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch ( haptic perception), as well as temperature ( thermoception), body position (proprioception), and pain. It ...
,
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
, and
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
, i.e., all information necessary for postural stability. Adaptive modifications in the central processing of sensory information take place to produce motor responses that are appropriate for the new gravitational environment. As a result, terrestrial motor strategies are progressively abandoned in weightlessness, as astronauts adapt to the weightless environment. This is particularly true for the major postural
muscles Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of musc ...
found in the lower legs. The modifications in posture, movement, and locomotion acquired in reduced gravity are then inappropriate for Earth's gravity upon return. After landing,
postural instability A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness, or wooziness, or having a sensation of movement, spinning, or floating. Balance ...
approaching clinical
ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
is manifested as a result of this in-flight neural reorganization. Difficulties with
standing Standing, also referred to as orthostasis, is a position in which the body is held in an ''erect'' ("orthostatic") position and supported only by the feet. Although seemingly static, the body rocks slightly back and forth from the ankle in the s ...
,
walking Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an ' inverted pendulum' gait in which the body vaults ...
, turning corners, climbing stairs, and a slowing of gait are experienced as astronauts re-adapt to Earth's gravity, until terrestrial motor strategies are fully re-acquired. Adaptation to spaceflight also induces a significant increase in the time required to traverse an obstacle course on landing day, and recovery of functional mobility takes an average of two weeks. These difficulties can have adverse consequences for an astronauts’ ability to stand up or escape from the vehicle during emergencies and to function effectively immediately after leaving the spacecraft after flight. Thus it is important to understand the cause of these profound impairments of posture and locomotion stability, and develop
countermeasures A countermeasure is a measure or action taken to counter or offset another one. As a general concept, it implies precision and is any technological or tactical solution or system designed to prevent an undesirable outcome in the process. The fi ...
. The most significant sensorimotor problems astronauts will face during a stay on the Moon and Mars are likely to occur when walking around in their
space suits A space suit or spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, vacuum and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, ...
. The suits are big and bulky and change the body's
center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force ma ...
. This along with the uneven terrain and limited field of view makes locomotion challenging.


Compensatory eye movements

The function of the vestibular system during spaceflight is by far the most carefully studied of all. This is especially true of the gravity-sensing
otolith organs An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The ...
and their relationship to
eye movement Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interest ...
s. The vestibular
semicircular canal In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line o ...
function seems unchanged in weightlessness because the horizontal eye movements that compensated for head yaw rotation are not affected by spaceflight. The absence of gravity stimulation of the otoliths reduces the torsional vestibulo-ocular reflex during head
roll Roll or Rolls may refer to: Movement about the longitudinal axis * Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis ** Roll (aviation) ...
rotation in microgravity. This deficit is absent when astronauts are exposed to
centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parall ...
s, suggesting that the adaptive CNS changes are taking place centrally rather than peripherally. During the first days in orbit, the asymmetry of vertical eye movements in response to moving visual scenes is inverted. A return to symmetry of the vestibulo-ocular and
optokinetic reflex The optokinetic response is a combination of a slow-phase and fast-phase eye movements. It is seen when an individual tracks (pursuit movement) a moving object with their eyes, which then moves out of the field of vision, a point at which their ...
es is then observed. Some studies have shown increased latencies and decreased peak velocities of
saccade A saccade ( , French for ''jerk'') is a quick, simultaneous movement of both eyes between two or more phases of fixation in the same direction.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishi ...
s, while others have found just the opposite. It is possible that these conflicting results depend on when the measures were obtained during the mission. There is also a serious disruption of
smooth pursuit In the scientific study of vision, smooth pursuit describes a type of eye movement in which the eyes remain fixated on a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movemen ...
eye movements, especially in the vertical plane. Human missions to Mars will include several transitions between different gravitational environments. These changes will eventually affect the reflex eye movements. A key question is whether astronauts can have different sets of reflexes among which they can rapidly switch based on the gravitational environment. Determination of the dual-adaptive capabilities of reflex eye movements in such circumstances is vitally important so that it can be determined to what extent the
Sensory-motor coupling Sensory-motor coupling is the coupling or integration of the sensory system and motor system. Sensorimotor integration is not a static process. For a given stimulus, there is no one single motor command. "Neural responses at almost every stage of a ...
skills acquired in one-g environment will transfer to others.


Spatial orientation

In
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
, astronauts must rely much more on vision to maintain their
spatial orientation In geometry, the orientation, angular position, attitude, bearing, or direction of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it occupies. More specifically, it refers to the imagin ...
, because the
otolith An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
organs can no longer signal the “down” direction. During prolonged exposure, however, reliance seems to shift toward an intrinsic, body vertical reference. The erroneous illusions of self-motion during head movements performed during and after return to Earth gravity are presumably due to a re-interpretation of vestibular inputs. Ground-based studies suggest that the CNS resolves the “tilt-translation” ambiguity based on the frequency content of the
linear acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by th ...
detected by the
otolith An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
organs, with low frequency indicating “tilt” and high frequency indicating “translation”. A crossover exists at about 0.3 Hz where the otolith signals are then ambiguous. Exposure to weightlessness presumably results in a shift of this crossover frequency, which could then contribute to spatial disorientation and SMS. Although investigations of higher cognitive processes, such as
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
and
mental rotation Mental rotation is the ability to rotate mental representations of two-dimensional and three-dimensional objects as it is related to the visual representation of such rotation within the human mind. There is a relationship between areas of the bra ...
are limited, the astronauts frequently report that the spacecraft interiors look longer and higher than they actually are, and a reduction in the perceived height of three-dimensional objects is observed in-flight compared with pre-flight, suggesting an alteration in the
mental representation A mental representation (or cognitive representation), in philosophy of mind, cognitive psychology, neuroscience, and cognitive science, is a hypothetical internal cognitive symbol that represents external reality, or else a mental process that ...
of three-dimensional cues in weightlessness.
Perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
is a model of the brain, a hypothesis about the world that presupposes the
Newton's laws of motion Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in moti ...
. These laws change in weightlessness and, therefore, one could expect changes in the mental representation of objects’ shape and distance during spaceflight. The rare investigations carried out in space so far have not demonstrated drastic changes, probably because the CNS continues to use an internal model of gravity, at least for a short while. It can be speculated that the way of processing three dimensions will be more developed after a long absence of a gravitational reference. Further investigations carried out in space will perhaps reveal that other higher cortical functions are impaired in weightless conditions. The combination of
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), e ...
with the measurement of
evoked potentials An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light ...
and
brain mapping Brain mapping is a set of neuroscience techniques predicated on the mapping of (biological) quantities or properties onto spatial representations of the (human or non-human) brain resulting in maps. According to the definition established in ...
on board the International Space Station should provide exciting results on the adaptive mechanisms of cerebral functions in weightlessness.


Neuroscience and space exploration

From Voskhod to the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ( ...
, spacecraft have improved in size and comfort and have allowed more and more people traveling into orbit. However, even with all of the human spaceflight experience gained over the past fifty years, no single completely effective countermeasure, or combination of countermeasures, exists against the negative effects of long-duration exposure to weightlessness. If a crew of astronauts were to embark on a six-month journey to Mars today, the countermeasures currently employed would presumably leave them less operational after landing. Many believe that physiological adaptation to Mars gravity (0.38 G) and re-adaptation to Earth gravity (1 G) would be enhanced by frequent exposure to
artificial gravity Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of re ...
on board the spacecraft en route to and from Mars. This would require an on-board human-rated
centrifuge A centrifuge is a device that uses centrifugal force to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities (e.g. cream from milk) or ...
or spacecraft rotation to produce a
centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parall ...
similar to gravity. This solution, while potentially effective, raises a number of operational, engineering, and physiological issues that will need to be addressed. The human physiological responses to long-duration exposure to anything other than zero-gravity or Earth's gravity are unknown. Research is needed to identify the minimum level, duration, and frequency of gravity level required to maintain normal CNS functions, as well as the importance of a gravity gradient across the body. The complex functioning of the CNS, even in the 1-G environment of Earth, has not revealed all its secrets. The most basic space neuroscience questions must be answered to minimize risks and optimize crew performance during transit and planetary operations. The results of this research will certainly find other applications in
medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...
and
biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used ...
. Our ability to understand how Earth's gravitational environment has shaped the evolution of sensory and motor systems can give us a clearer understanding of the fundamental mechanisms of CNS functions. Knowledge of the effects of gravity on CNS functions in humans, as well as elucidation of the basic mechanisms by which these effects occur, will be of direct benefit to understanding the impact of, and providing countermeasures for, long-term exposure of humans to the
weightlessness Weightlessness is the complete or near-complete absence of the sensation of weight. It is also termed zero gravity, zero G-force, or zero-G. Weight is a measurement of the force on an object at rest in a relatively strong gravitational fie ...
of spaceflight and the partial gravity of
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
and
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
bases.


See also

*
Effect of spaceflight on the human body Venturing into the environment of space can have negative effects on the human body. Significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton ( spaceflight osteopenia). Other significant ef ...


References


External links


Space Neuroscience Research



Human Physiology in Space
* {{DEFAULTSORT:Neuroscience Neuroscience Behavioral neuroscience Space medicine