Coriolis effect (perception)

Last updated July 05, 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 as at a constant rate so 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, and measures angular acceleration within its plane.
The vestibular system contains a leaky integrator, which integrates the angular acceleration to sense the current angular velocity. However, due to leaking, the sensed angular velocity returns to zero after a while (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

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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.

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

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

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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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