Coriolis effect (perception)

Last updated September 15, 2024

In psychophysical perception, the Coriolis effect (also referred to as the Coriolis illusion or the vestibular Coriolis effect) is the misperception of body orientation due to head movement while under the effect of rotation, often inducing nausea.^[1]^[2]^[3] This effect comes about as the head is moved in contrary or similar motion with the body during the time of a spin. This goes on to affect the vestibular system, particularly the semicircular canals which are affected by the acceleration. This causes a sense of dizziness or nausea before equilibrium is restored after the head returns to a stabilized state.^[4]^[5] Crucially, this illusion is based entirely upon perception, and is largely due to conflicting signals between one's sight and one's perception of their body position or motion.^[6] Examples of situations where this can arise are circular acceleration and movement during a circular rotation. ^[7]

There is also the pseudo-Coriolis effect (also referred to as the optokinetic pseudo-Coriolis effect), which takes place when there is no physical circular movement, only visual.^[8]^[9] Perceptually it feels the same as the Coriolis effect, being perceived as self motion inducing the same kind of nausea and often the cause of motion sickness.

Causes and effects

The physiological mechanism by which the effect occurs is all contained within the semicircular canals, as determined by head tilt. When rotating and tilting a person's head, the endolymphatic fluid within the canal may be subjected to the Coriolis force.^[10] This occurs when the motion is at a constant rate such that the fluid and the canals move at the same rate, causing the sensation of rotation to disappear. When interrupted by a head movement, the fluid will move at an angle, affecting the cupula, which will cause a perceived rotation that is not occurring.^[11]^[12]

This most often occurs when a person's head is moved out of alignment during a spin. If individuals are spinning to the left along their y-axis and then push their head forward, that will bring their heads out of alignment and make it subject to Coriolis force and resultant effect. The manifestation of this effect is that the individuals will feel like their heads are tilting to their left.^[4]

This can cause nausea, disorientation, and vomiting resulting from motion sickness. These feelings of discomfort arise in the body due to a variety of signals when the signals being sent by the vestibular system and visual system are not in agreement, i.e. the eyes may be telling the body that one is not moving, but the vestibular systems' fine-tuned senses are detecting and communicating the opposite.^[13]

Examples

The Coriolis effect is a concern for pilots and astronauts, where it can cause extreme disorientation.^[14]^[15]^[5]^[16]^[17] This happens as pilots turn or rotate their aircraft, while also turning their head. It has been noted as difficult to report, as oftentimes the sensation is difficult to describe.^[5] In extreme situations, this can cause the pilot to lose control of the aircraft.^[18] Due to the possible dangers of this, pilots are often trained physiologically, such as in a Bárány chair, to prepare for such circumstances, along with being trained to trust their flying instruments rather than their own visual perceptions.^[12]

The pseudo-Coriolis effect often occurs in VR simulations, where it can be perceived that motion is occurring without the body itself moving.^[19]

The Bárány chair demonstration

The Bárány chair is often used in the following way:^[20]

The subject sits in the chair with head down and eyes closed.
The chair is spun up to a below-threshold speed ( $<2\;\mathrm {deg/s}$ ). The subject does not feel rotation.
The chair is spun up to above-threshold speed. The subject feels rotation for a while.
Eventually in about 30 seconds, the feeling of rotation stops due to adaptation.
The chair is abruptly stopped, and the subject raises head up and opens eyes. The vestibular system signals as if the head is rotating side-to-side (in the coronal plane), but the vision system signals as if the head is not moving.

The explanation is as follows:^[21]

Each of the three semicircular canals is effectively a damped oscillator with low inertia. When one rotates in space, the fluid in the canal rotates in the other direction, and this translates to neural signals indicating the current angular velocity.
However, if the angular velocity remains stable, the fluids would eventually become equal with the walls again, and the sensed angular velocity returns to zero (adaptation).
After abruptly stopping and raising the head, the fluid in the semicircular canal in the coronal plane flows in the opposite direction due to Coriolis effect, creating an illusory rotation, similar to the Compton generator.

History

The term was first applied to perception by G. Schubert in 1954, where it was termed the vestibular Coriolis effect, since he hypothesized that it was caused by Coriolis force within the semicircular canals.^[22]^[10]

The Coriolis force was discovered by Gaspard-Gustave de Coriolis in 1832. By the end of the 19th century, Coriolis force had become a common phrase in meteorological literature.^[23] Coriolis force is classified as a fictitious force in rotating reference frames.^[24]

Related Research Articles

Motion sickness occurs due to a difference between actual and expected motion. Symptoms commonly include nausea, vomiting, cold sweat, headache, dizziness, tiredness, loss of appetite, and increased salivation. Complications may rarely include dehydration, electrolyte problems, or a lower esophageal tear.

<span class="mw-page-title-main">Sense of balance</span> Physiological sense regarding posture

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The semicircular canals are three semicircular interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the lateral, anterior and posterior semicircular canals. They are the part of the bony labyrinth, a periosteum-lined cavity on the petrous part of the temporal bone filled with perilymph.

The vestibulo-ocular reflex (VOR) is a reflex that acts to stabilize gaze during head movement, with eye movement due to activation of the vestibular system, it is also known as the Cervico-ocular reflex. The reflex acts to stabilize images on the retinas of the eye during head movement. Gaze is held steadily on a location by producing eye movements in the direction opposite that of head movement. For example, when the head moves to the right, the eyes move to the left, meaning the image a person sees stays the same even though the head has turned. Since slight head movement is present all the time, VOR is necessary for stabilizing vision: people with an impaired reflex find it difficult to read using print, because the eyes do not stabilise during small head tremors, and also because damage to reflex can cause nystagmus.

The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear in most mammals.

<span class="mw-page-title-main">Space adaptation syndrome</span> Condition caused by weightlessness

Space adaptation syndrome (SAS) or space sickness is a condition experienced by as many as half of all space travelers during their adaptation to weightlessness once in orbit. It is the opposite of terrestrial motion sickness since it occurs when the environment and the person appear visually to be in motion relative to one another even though there is no corresponding sensation of bodily movement originating from the vestibular system.

<span class="mw-page-title-main">Dizziness</span> Neurological condition causing impairment in spatial perception and stability

Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.

Spatial disorientation is the inability to determine position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular system, and proprioceptive system collectively work to coordinate movement with balance, and can also create illusory nonvisual sensations, resulting in spatial disorientation in the absence of strong visual cues.

<span class="mw-page-title-main">Benign paroxysmal positional vertigo</span> Medical condition

Benign paroxysmal positional vertigo (BPPV) is a disorder arising from a problem in the inner ear. Symptoms are repeated, brief periods of vertigo with movement, characterized by a spinning sensation upon changes in the position of the head. This can occur with turning in bed or changing position. Each episode of vertigo typically lasts less than one minute. Nausea is commonly associated. BPPV is one of the most common causes of vertigo.

<span class="mw-page-title-main">Motion simulator</span> Type of mechanism

A motion simulator or motion platform is a mechanism that creates the feelings of being in a real motion environment. In a simulator, the movement is synchronised with a visual display of the outside world (OTW) scene. Motion platforms can provide movement in all of the six degrees of freedom (DOF) that can be experienced by an object that is free to move, such as an aircraft or spacecraft:. These are the three rotational degrees of freedom and three translational or linear degrees of freedom.

<span class="mw-page-title-main">Vertigo</span> Type of dizziness where a person has the sensation of moving or surrounding objects moving

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In aviation, a graveyard spiral is a type of dangerous spiral dive entered into accidentally by a pilot who is not trained or not proficient in flying in instrument meteorological conditions (IMC). Other names for this phenomenon include suicide spiral, deadly spiral, death spiral and vicious spiral.

Illusions of self-motion occur when one perceives bodily motion despite no movement taking place. One can experience illusory movements of the whole body or of individual body parts, such as arms or legs.

The spins is an adverse reaction of intoxication that causes a state of vertigo and nausea, causing one to feel as if "spinning out of control", especially when lying down. It is most commonly associated with drunkenness or mixing alcohol with other psychoactive drugs such as cannabis. This state is likely to cause vomiting, but having "the spins" is not life-threatening unless pulmonary aspiration occurs.

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The leans is the most common type of spatial disorientation for aviators. Through stabilization of the fluid in the semicircular canals, a pilot may perceive straight and level flight while actually in a banked turn. This is caused by a quick return to level flight after a gradual, prolonged turn that the pilot failed to notice. The phenomenon consists of a false perception of angular displacement about the roll axis and therefore becomes an illusion of bank. This illusion is often associated with a vestibulospinal reflex that results in the pilot actually leaning in the direction of the falsely perceived vertical. Other common explanations of the leans are due to deficiencies of both otolith-organ and semicircular-duct sensory mechanisms.

Space neuroscience or astroneuroscience is the scientific study of the central nervous system (CNS) functions during spaceflight. Living systems can integrate the inputs from the senses to navigate in their environment and to coordinate posture, locomotion, and eye movements. Gravity has a fundamental role in controlling these functions. In weightlessness during spaceflight, integrating the sensory inputs and coordinating motor responses is harder to do because gravity is no longer sensed during free-fall. For example, the otolith organs of the vestibular system no longer signal head tilt relative to gravity when standing. 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, which affects spatial orientation and mental representation. Dysfunctions of the vestibular system are common during and immediately after spaceflight, such as space motion sickness in orbit and balance disorders after return to Earth.

Simulator sickness is a subset of motion sickness that is typically experienced while playing video games from first-person perspective. It was discovered in the context of aircraft pilots who undergo training for extended periods of time in flight simulators. Due to the spatial limitations imposed on these simulators, perceived discrepancies between the motion of the simulator and that of the vehicle can occur and lead to simulator sickness. It is similar to motion sickness in many ways, but occurs in simulated environments and can be induced without actual motion. Symptoms of simulator sickness include discomfort, apathy, drowsiness, disorientation, fatigue, and nausea. These symptoms can reduce the effectiveness of simulators in flight training and result in systematic consequences such as decreased simulator use, compromised training, ground safety, and flight safety. Pilots are less likely to want to repeat the experience in a simulator if they have suffered from simulator sickness and hence can reduce the number of potential users. It can also compromise training in two safety-critical ways:

It can distract the pilot during training sessions.
It can cause the pilot to adopt certain counterproductive behaviors to prevent symptoms from occurring.

Virtual reality sickness occurs when exposure to a virtual environment causes symptoms that are similar to motion sickness symptoms. The most common symptoms are general discomfort, eye strain, headache, stomach awareness, nausea, vomiting, pallor, sweating, fatigue, drowsiness, disorientation, and apathy. Other symptoms include postural instability and retching. Common causes are low frame rate, input lag, and the vergence-accommodation-conflict.

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