![Vestibular balance system](https://upload.wikimedia.org/wikipedia/commons/7/7a/Vestibular_balance_system.jpg)
The vestibular system, in
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s, is a
sensory system
The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain involved i ...
that creates the
sense of balance
The sense of balance or equilibrioception is the perception of balance and spatial orientation. It helps prevent humans and nonhuman animals from falling over when standing or moving. Equilibrioception is the result of a number of sensory systems ...
and
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 ...
for the purpose of coordinating
movement
Movement may refer to:
Common uses
* Movement (clockwork), the internal mechanism of a timepiece
* Motion, commonly referred to as movement
Arts, entertainment, and media
Literature
* "Movement" (short story), a short story by Nancy Fu ...
with balance. Together with the
cochlea
The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory org ...
, a part of the
auditory system
The auditory system is the sensory system for the sense of hearing. It includes both the sensory organs (the ears) and the auditory parts of the sensory system.
System overview
The outer ear funnels sound vibrations to the eardrum, increasin ...
, it constitutes the
labyrinth of the inner ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...
in most mammals.
As movements consist of rotations and translations, the vestibular system comprises two components: the
semicircular canals
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
Structure
The ...
, which indicate
rotational movements; and 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 ...
s, which indicate
linear accelerations. The vestibular system sends signals primarily to the neural structures that control
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 interests. ...
; these provide the anatomical basis of the
vestibulo-ocular reflex, which is required for clear vision. Signals are also sent to the muscles that keep an animal upright and in general control
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 ...
; these provide the anatomical means required to enable an animal to maintain its desired position in space.
The brain uses information from the vestibular system in the head and from
proprioception
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
throughout the body to enable the animal to understand its body's
dynamics and
kinematics
Kinematics is a subfield of physics, developed in classical mechanics, that describes the Motion (physics), motion of points, Physical object, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause ...
(including its position and acceleration) from moment to moment. How these two perceptive sources are integrated to provide the underlying structure of the
sensorium
A sensorium (/sɛnˈsɔːrɪəm/) (plural: sensoria) is the apparatus of an organism's perception considered as a whole, the "seat of sensation" where it experiences, perceives and interprets the environments within which it lives. The term origi ...
is unknown.
Semicircular canal system
![Cochlea and vestibular system](https://upload.wikimedia.org/wikipedia/commons/d/d1/Cochlea_and_vestibular_system.gif)
The semicircular canal system detects rotational movements. The semicircular canals are its main tools to achieve this detection.
Structure
Since the world is three-dimensional, the vestibular system contains three
semicircular canals
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
Structure
The ...
in each
labyrinth
In Greek mythology, the Labyrinth (, ) was an elaborate, confusing structure designed and built by the legendary artificer Daedalus for King Minos of Crete at Knossos. Its function was to hold the Minotaur, the monster eventually killed by the ...
. They are approximately
orthogonal
In mathematics, orthogonality is the generalization of the geometric notion of ''perpendicularity''.
By extension, orthogonality is also used to refer to the separation of specific features of a system. The term also has specialized meanings in ...
(at right angles) to each other, and are the ''
horizontal'' (or ''lateral''), the ''
anterior semicircular canal
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals.
Structure
The ...
'' (or ''superior''), and the ''
posterior'' (or ''inferior'') semicircular canal. Anterior and posterior canals may collectively be called ''vertical semicircular canals''.
* Movement of fluid within the horizontal semicircular canal corresponds to rotation of the head around a vertical axis (i.e. the neck), as when doing a
pirouette
In dance and gymnastics, a turn is a rotation of the body about the vertical axis. It is usually a complete rotation of the body, although quarter (90°) and half (180°) turns are possible for some types of turns. Multiple, consecutive turns are ...
.
* The anterior and posterior semicircular canals detect rotations of the head in the
sagittal plane
The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divid ...
(as when nodding), and in the
frontal plane
The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes.
Details
The coronal plane is an example of a longitud ...
, as when
cartwheeling
A cartwheel is a sideways rotary movement of the body. It is performed by bringing the hands to the floor one at a time while the body inverts. The legs travel over the body trunk while one or both hands are on the floor, and then the feet ret ...
. Both anterior and posterior canals are oriented at approximately 45° between frontal and sagittal planes.
The movement of fluid pushes on a structure called the
cupula which contains hair cells that transduce the mechanical movement to electrical signals.
Push-pull systems
The canals are arranged in such a way that each canal on the left side has an almost parallel counterpart on the right side. Each of these three pairs works in a ''push-pull'' fashion: when one canal is stimulated, its corresponding partner on the other side is inhibited, and vice versa.
This push-pull system makes it possible to sense all directions of rotation: while the ''right horizontal canal'' gets stimulated during head rotations to the right (Fig 2), the ''left horizontal canal'' gets stimulated (and thus predominantly signals) by head rotations to the left.
Vertical canals are coupled in a crossed fashion, i.e. stimulations that are excitatory for an anterior canal are also inhibitory for the contralateral posterior, and vice versa.
Vestibulo-ocular reflex (VOR)
The vestibulo-ocular reflex (VOR) is a
reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
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 interests. ...
that stabilizes images on the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
during head movement by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field. For example, when the head moves to the right, the eyes move to the left, and vice versa. Since slight head movements are present all the time, the VOR is very important for stabilizing vision: patients whose VOR is impaired find it difficult to read, because they cannot stabilize the eyes during small head tremors. The VOR reflex does not depend on visual input and works even in total darkness or when the eyes are closed.
This reflex, combined with the push-pull principle described above, forms the physiological basis of the ''Rapid head impulse test'' or ''Halmagyi-Curthoys-test'', in which the head is rapidly and forcefully moved to the side while observing whether the eyes keep looking in the same direction.
Mechanics
The mechanics of the semicircular canals can be described by a damped oscillator. If we designate the deflection of the cupula with
, and the head velocity with
, the cupula deflection is approximately
:
α is a proportionality factor, and ''s'' corresponds to the frequency. For humans, the time constants T
1 and T
2 are approximately 3 ms and 5 s, respectively. As a result, for typical head movements, which cover the frequency range of 0.1 Hz and 10 Hz, the deflection of the cupula is approximately proportional to the head-velocity. This is very useful since the velocity of the eyes must be opposite to the velocity of the head in order to maintain clear vision.
Central processing
Signals from the vestibular system also project to the cerebellum (where they are used to keep the VOR effective, a task usually referred to as ''learning'' or ''adaptation'') and to different areas in the cortex. The projections to the cortex are spread out over different areas, and their implications are currently not clearly understood.
Projection pathways
The vestibular nuclei on either side of the brainstem exchange signals regarding movement and body position. These signals are sent down the following projection pathways.
* To the
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
. Signals sent to the cerebellum are relayed back as muscle movements of the head, eyes, and posture.
* To nuclei of cranial nerves
III,
IV, and
VI. Signals sent to these nerves cause the vestibulo-ocular reflex. They allow for the eyes to fix on a moving object while staying in focus.
* To the
reticular formation
The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation ...
. Signals sent to the reticular formation signal the new posture the body has taken on, and how to adjust circulation and breathing due to body position.
* To the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...
. Signals sent to the spinal cord allow quick reflex reactions to both the limbs and trunk to regain balance.
* To the
thalamus
The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...
. Signals sent to the thalamus allow for head and body motor control as well as being conscious of body position.
Otolithic organs
While the semicircular canals respond to rotations, the
otolithic 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 (ear), utricle of the inner ear, specifically in the vestibular system of verteb ...
sense linear accelerations. Humans have two otolithic organs on each side, one called the
utricle, the other called the
saccule
The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves verticall ...
. The utricle contains a patch of
hair cell
Hair cells are the sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates, and in the lateral line organ of fishes. Through mechanotransduction, hair cells detect movement in their environment. ...
s and supporting cells called a
macula
The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...
. Similarly, the saccule contains a patch of hair cells and a
macula
The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...
. Each hair cell of a macula has forty to seventy stereocilia and one true cilium called a
kinocilium
A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear.
Anatomy in humans
Kinocilia are found on the apical surface of hair cells and are involved in both the morphogenesis ...
. The tips of these cilia are embedded in an otolithic membrane. This membrane is weighted down with protein-calcium carbonate granules called otoconia. These otoconia add to the weight and inertia of the membrane and enhance the sense of gravity and motion. With the head erect, the otolithic membrane bears directly down on the hair cells and stimulation is minimal. When the head is tilted, however, the otolithic membrane sags and bends the stereocilia, stimulating the hair cells. Any orientation of the head causes a combination of stimulation to the utricles and saccules of the two ears. The brain interprets head orientation by comparing these inputs to each other and to other input from the eyes and stretch receptors in the neck, thereby detecting whether the head is tilted or the entire body is tipping.
Essentially, these otolithic organs sense how quickly you are accelerating forward or backward, left or right, or up or down.
Most of the utricular signals elicit eye movements, while the majority of the saccular signals projects to muscles that control our posture.
While the interpretation of the rotation signals from the semicircular canals is straightforward, the interpretation of otolith signals is more difficult: since gravity is equivalent to a constant linear acceleration, one somehow has to distinguish otolith signals that are caused by linear movements from those caused by gravity. Humans can do that quite well, but the neural mechanisms underlying this separation are not yet fully understood.
Humans can sense head tilting and linear acceleration even in dark environments because of the orientation of two groups of hair cell bundles on either side of the
striola. Hair cells on opposite sides move with mirror symmetry, so when one side is moved, the other is inhibited. The opposing effects caused by a tilt of the head cause differential sensory inputs from the hair cell bundles allow humans to tell which way the head is tilting.
Sensory information is then sent to the brain, which can respond with appropriate corrective actions to the nervous and muscular systems to ensure that balance and awareness are maintained.
Experience from the vestibular system
Experience from the vestibular system is called
equilibrioception
The sense of balance or equilibrioception is the perception of balance and spatial orientation. It helps prevent humans and nonhuman animals from falling over when standing or moving. Equilibrioception is the result of a number of sensory systems ...
. It is mainly used for the sense of
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 Bulgarian ...
and for
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 ...
. When the vestibular system is stimulated without any other inputs, one experiences a sense of self-motion. For example, a person in complete darkness and sitting in a chair will sense that he or she has turned to the left if the chair is turned to the left. A person in an
elevator
An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
, with essentially constant visual input, will sense she is descending as the elevator starts to descend. There are a variety of direct and indirect vestibular stimuli which can make people sense they are moving when they are not, not moving when they are, tilted when they are not, or not tilted when they are. Although the vestibular system is a very fast sense used to generate reflexes, including the
righting reflex The righting reflex, also known as the labyrinthine righting reflex, is a reflex that corrects the orientation of the body when it is taken out of its normal upright position. It is initiated by the vestibular system, which detects that the body is ...
, to maintain perceptual and postural stability, compared to the other senses of vision, touch and audition, vestibular input is perceived with delay.
Pathologies
Diseases of the vestibular system can take different forms, and usually induce
vertigo
Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...
and instability or loss of balance, often accompanied by nausea. The most common vestibular diseases in humans are
vestibular neuritis
Labyrinthitis is inflammation of the labyrinth – a maze of fluid-filled channels in the inner ear. Vestibular neuritis is inflammation of the vestibular nerve – the nerve in the inner ear that sends messages related to motion and position t ...
, a related condition called
labyrinthitis
Labyrinthitis is inflammation of the labyrinth – a maze of fluid-filled channels in the inner ear. Vestibular neuritis is inflammation of the vestibular nerve – the nerve in the inner ear that sends messages related to motion and position t ...
,
Ménière's disease
Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initial ...
, and
BPPV
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.
* T ...
. In addition, the function of the vestibular system can be affected by tumors on the
vestibulocochlear nerve
The vestibulocochlear nerve or auditory vestibular nerve, also known as the eighth cranial nerve, cranial nerve VIII, or simply CN VIII, is a cranial nerve that transmits sound and equilibrium (balance) information from the inner ear to the bra ...
, an infarct in the brain stem or in cortical regions related to the processing of vestibular signals, and cerebellar atrophy.
Since a function of the vestibular hair cells is to detect levels of carbon dioxide in the blood and to transmit such information to the brain, a loss of vestibular hair cells can cause death.
When the vestibular system and the visual system deliver incongruous results, nausea often occurs. When the vestibular system reports movement but the visual system reports no movement, the motion disorientation is often called
motion sickness
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 d ...
(or seasickness, car sickness, simulation sickness, or airsickness). In the opposite case, such as when a person is in a zero-gravity environment or during a virtual reality session, the disoriented sensation is often called
space sickness
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 whe ...
or
space adaptation syndrome
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 ...
. Either of these "sicknesses" usually ceases once the congruity between the two systems is restored.
Alcohol can also cause alterations in the vestibular system for short periods and will result in vertigo and possibly
nystagmus
Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...
due to the variable viscosity of the blood and the endolymph during the consumption of alcohol. The term for this is
positional alcohol nystagmus (PAN):
* PAN I - The alcohol concentration is higher in the blood than in the vestibular system, hence the endolymph is relatively dense.
* PAN II - The alcohol concentration is lower in the blood than in the vestibular system, hence the endolymph is relatively dilute.
PAN I will result in subjective vertigo in one direction and typically occurs shortly after ingestion of alcohol when blood alcohol levels are highest. PAN II will eventually cause subjective vertigo in the opposite direction. This occurs several hours after ingestion and after a relative reduction in blood alcohol levels.
Benign paroxysmal positional vertigo
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.
* T ...
(BPPV) is a condition resulting in acute symptoms of vertigo. It is probably caused when pieces that have broken off otoliths have slipped into one of the semicircular canals. In most cases, it is the posterior canal that is affected. In certain head positions, these particles shift and create a fluid wave which displaces the cupula of the canal affected, which leads to dizziness, vertigo and nystagmus.
A similar condition to BPPV may occur in dogs and other mammals, but the term ''vertigo'' cannot be applied because it refers to subjective perception. Terminology is not standardized for this condition.
A common vestibular pathology of dogs and cats is colloquially known as "old dog vestibular disease", or more formally idiopathic peripheral vestibular disease, which causes sudden episode of loss of balance, circling, head tilt, and other signs. This condition is very rare in young dogs but fairly common in geriatric animals, and may affect cats of any age.
Vestibular dysfunction has also been found to correlate with cognitive and emotional disorders, including
depersonalization
Depersonalization can consist of a detachment within the self, regarding one's mind or body, or being a detached observer of oneself. Subjects feel they have changed and that the world has become vague, dreamlike, less real, lacking in significa ...
and
derealization
Derealization is an alteration in the perception of the external world, causing those with the condition to perceive it as unreal, distant, distorted or falsified. Other symptoms include feeling as if one's environment is lacking in spontaneity, ...
.
Other vertebrates
Though humans as well as most other vertebrates exhibit three semicircular canals in their vestibular systems,
Lamprey
Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like s ...
s and
Hagfish
Hagfish, of the class Myxini (also known as Hyperotreti) and order Myxiniformes , are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, a ...
are vertebrates that deviate from this trend. The vestibular systems of lampreys contain two semicircular canals while those of hagfish contain a single canal. The lamprey's two canals are developmentally similar to the anterior and posterior canals found in humans. The single canal found in hagfish appears to be secondarily derived.
Additionally, the vestibular systems of lampreys and hagfish differ from those found in other vertebrates in that the otolithic organs of lampreys and hagfish are not segmented like the utricle and saccule found in humans, but rather form one continuous structure referred to as the macula communis.
Birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
possess a ''second'' vestibular organ in the back, the lumbosacral canals. Behavioral evidence suggests that this system is responsible for stabilizing the body during
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 o ...
and
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 ...
.
Invertebrates
A large variety of vestibular organs are present in invertebrates. A well-known example are the halteres of
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
(Diptera) which are modified hind wings.
See also
*
Dark cell
Dark cells are specialized nonsensory epithelial cells found on either side of the vestibular organs, and lining the endolymphatic space. These dark-cell areas in the vestibular organ are structures involved in the production of endolymph, an in ...
*
Migraine-associated vertigo
Vestibular migraine (VM) is vertigo with migraine, either as a symptom of migraine or as a related neurological disorder.
A 2010 report from the University of British Columbia published in the journal '' Headache'' said that Migraine associate ...
*
Statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in ''Xenoturbella''. The statocyst cons ...
References
Further reading
* (Comment: For clinicians, and other professionals working with dizzy patients.)
* (Comment: Research on driver or motion-induced sleepiness aka '
sopite syndrome
The sopite syndrome (; Latin: sopire, "to lay to rest, to put to sleep") is a neurological disorder that relates symptoms of fatigue, drowsiness, and mood changes to prolonged periods of motion. raybiel, A., & Knepton, J. (1976), "Sopite Syndrome - ...
' links it to the vestibular labyrinths.)
*
* (Comment: A book for experts, summarizing the state of the art in our understanding of the balance system)
* Lawson, Ben D; Rupert, Angus H; Kelley, Amanda M
"Mental Disorders Comorbid with Vestibular Pathology" A preview of an article on how vestibular disorders can cause symptoms that look like mental disorders.
External links
Vestibular Disorders AssociationFor more information about vestibular (inner ear balance) disorders.
(Video) Head Impulse Testing site(vHIT) Site with thorough information about vHIT
SensesWeb, which contains animations of all sensory systems, and additional links.
Dizzytimes.com Online Community for Sufferers of Vertigo and Dizziness.
''Neuroscience Online'' (electronic neuroscience textbook)
{{Authority control
Nervous system
Sensory systems