A quantitative study of vestibular adaptation in humans.
TL;DR: A mathematical model for short-term adaptation to vestibular stimuli is presented, and it is suggested that previous values quoted for Tc represent underestimates of the true value owing to superposition of the adaptive term here described.
Abstract: A mathematical model for short-term adaptation to vestibular stimuli is presented. A transfer function is derived relating slow phase angular velocity of resulting nystagmus to the angular velocity of head rotation. The resulting model has been tested by comparing its responses to controlled step and ramp angular velocity stimuli with those of 8 human subjects, and in all cases a close match was obtained. The mean time constant of the adaptive term was 82 sec (S.E.±6.5) and the mean cupular restoration time constant (Tc) was 21 sec (S.E.±1.5). It is suggested that previous values quoted for Tc represent underestimates of the true value owing to superposition of the adaptive term here described. The adaptive term accounts well for the phenomenon of secondary nystagmus, especially during either strong stimuli or prolonged rotations. Some implications of the findings in relation to clinical and aviation medicine are discussed.
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01 Jan 1974
TL;DR: To appreciate this material in relation to daily experiences, it is necessary to consider why vestibular sensations do not typically achieve conscious awareness during natural voluntary head and body movement.
Abstract: During natural movement on the earth’s surface, we are seldom aware of vestibular sensations, and when we do become aware of them, they usually signify an unnatural stimulus or an abnormality of vestibular function. With specially contrived conditions of observation, relationships between acceleratory stimuli and vestibular sensations and perceptions can be described quantitatively and qualitatively. These relationships constitute the primary subject matter of this chapter, but to appreciate this material in relation to daily experiences, we must first consider why vestibular sensations do not typically achieve conscious awareness during natural voluntary head and body movement.
389 citations
TL;DR: The sections in this article are: Purposes of eye Movements, Plasticity and Repair, and Neurophysiology of Vergence and Vergence Movements.
Abstract: The sections in this article are:
1
Purposes of eye Movements
1.1
Vestibuloocular Reflex
1.2
Afoveate Saccadic System
1.3
Optokinetic System
1.4
Visual Stabilization
1.5
Pursuit System
1.6
Saccadic System
1.7
Vergence System
2
Oculomotor Plant
2.1
Motoneuron Behavior
2.2
Movement and Muscle Fiber Types
2.3
Stretch Afferents
2.4
Muscle Mechanics
3
Vestibuloocular Reflex
3.1
Properties of Reflex
3.2
Semicircular Canals
3.3
Central Pathways
3.4
Otolith Reflex
3.5
Neurophysiology of Reflex
4
Optokinetic System
4.1
Properties of Optokinetic Nystagmus
4.2
Model of Optokinetic-Vestibular Cooperation
4.3
Neurophysiology of Optokinetic System
5
Saccadic System
5.1
Properties of Rapid Eye Movements
5.2
Properties of Quick-Phase System
5.3
Properties of Saccadic System
5.4
Neurophysiology of Saccades
6
Pursuit System
6.1
Stabilization System
6.2
Properties of Pursuit
6.3
Neurophysiology of Pursuit
6.4
Models of Pursuit
7
Vergence System
7.1
Properties of Vergence Movements
7.2
Neurophysiology of Vergence
8
Plasticity and Repair
8.1
Gain of Vestibuloocular Reflex
8.2
Recovery from VIIIth Nerve Lesions
8.3
Saccadic Plasticity
8.4
Plasticity of Vergence Tone
9
Measuring Eye Movements
9.1
Noncontact Methods
9.2
Contact Methods
365 citations
01 Jan 1974
TL;DR: This chapter examines the vestibular organs from a systems point of view in an attempt to describe their primary functions as well as the integrated operations of their essential elements.
Abstract: This chapter examines the vestibular organs from a systems point of view in an attempt to describe their primary functions as well as the integrated operations of their essential elements. The examination is guided in large part by the analogy which is shown to exist between the vestibular system and the human-contrived inertial guidance system currently utilized in aerospace and submarine navigation. The operation of both systems can be shown to be based upon the same laws of physics, to embody analogous elements, to perform similar operations, and to provide analogous information.
275 citations
TL;DR: A Bayesian model of the statistically optimal combination of noisy vestibular and visual signals is presented and can explain some well-known phenomena including the perception of upright in zero gravity, the Aubert effect, and the somatogravic illusion.
Abstract: The otoliths are stimulated in the same fashion by gravitational and inertial forces, so otolith signals are ambiguous indicators of self-orientation. The ambiguity can be resolved with added visual information indicating orientation and acceleration with respect to the earth. Here we present a Bayesian model of the statistically optimal combination of noisy vestibular and visual signals. Likelihoods associated with sensory measurements are represented in an orientation/acceleration space. The likelihood function associated with the otolith signal illustrates the ambiguity; there is no unique solution for self-orientation or acceleration. Likelihood functions associated with other sensory signals can resolve this ambiguity. In addition, we propose two priors, each acting on a dimension in the orientation/acceleration space: the idiotropic prior and the no-acceleration prior. We conducted experiments using a motion platform and attached visual display to examine the influence of visual signals on the interpretation of the otolith signal. Subjects made pitch and acceleration judgments as the vestibular and visual signals were manipulated independently. Predictions of the model were confirmed: (1) visual signals affected the interpretation of the otolith signal, (2) less variable signals had more influence on perceived orientation and acceleration than more variable ones, and (3) combined estimates were more precise than single-cue estimates. We also show that the model can explain some well-known phenomena including the perception of upright in zero gravity, the Aubert effect, and the somatogravic illusion.
206 citations
Cites background from "A quantitative study of vestibular ..."
...…by Knill and Saunders, 2003; Hillis et al. 2004), and (3) the sensory estimators are unbiased, meaning that their signal values by themselves are interpreted correctly (this assumption is also reasonable because sensory systems become calibrated during the lifespan, Malcolm and Melvill-Jones 1970)....
[...]
TL;DR: The main features of these results can be explained by an analytic model that incorporates a central velocity-storage mechanism that perseverates vestibular inputs, Ewald's second law, and adaptation of primary Vestibular afferent activity.
188 citations
References
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TL;DR: The cupula-endolymph system has to be considered as a heavily damped torsion pendulum, which has a differential equation with solutions available in every handbook on mechanics and which ought to predict any conduct of the cupula found in practice.
Abstract: When Steinhausen (1931) discovered that the cupula terminalis in the semicircular canal reaches the top of the ampulla, fitting hermetically in it, and when he moreover observed that a deviation of the cupula, caused by an endolymph flow, gradually decreases because of the directional force of the cupula, the theory of the semicircular canal underwent a significant change. Up till then there was held to be a narrow canal in which an endolymph-flow would soon be stopped by frictional damping. After a clinical turning test the endolymph would flow for about 0 5 sec. only, and then every part of the canal would be at rest. The prolonged after-sensations of 30 sec. or more could not be explained by the mechanical properties of the canal. They then had to be ascribed to a 'central origin', the only possible means of surmounting this difficulty (Mach, 1875; Gaede, 1922). Steinhausen gave the cupula its proper prominence. The endolymph after a sudden arrest of the turning chair will indeed flow on for about 05 sec., but the cupula is forced to bend and after having attained its maximal deviation, without further external forces acting, it will try to recover its former position of zero deviation. This process may take from 1 to 60 sec., depending on the rate of the angular velocity just before the sudden arrest. The prolonged aftersensations appear to have a very simple mechanical origin. As Steinhausen pointed out, the cupula-endolymph system has to be considered as a heavily damped torsion pendulum. It thus has a differential equation with solutions available in every handbook on mechanics. This statement, important as it may be, brings us no further if the constants of the equation for this case cannot be determined, but if they are known this equation ought to predict any conduct of the cupula found in practice. Steinhausen did not establish the values of the constants for his test animal, the pike. So he was unable to prove the hypothesis of the torsion pendulum with its consequences. We have determined these values for the human subject by means of experiments based on mechanical principles.
326 citations
TL;DR: The electrical activity of the vestibular nerve has been studied by Ross, who recorded impulses in single fibres in the frog and was able to distinguish the discharges due to the various parts of the labyrinth, but hitherto the Mammalia Vestibular organs have not been investigated in this way.
Abstract: The electrical activity of the vestibular nerve has been studied by Ross [1936], who recorded impulses in single fibres in the frog and was able to distinguish the discharges due to the various parts of the labyrinth. Sand [1938] and L6wenstein & Sand [1936, 1940] have made similar records from the dogfish and ray, but hitherto the Mammalia vestibular organs have not been investigated in this way. One reason for this is no doubt the great prominence of the cochlea activity in the 8th nerve of mammals and another the difficulty of reaching the vestibular fibres without interfering with the blood supply to the organ. In the present work this difficulty has been avoided by the use of a fine wire electrode thrust into the brain stem in the region of the vestibular nucleus so as to pick up impulses from the entering bundles of vestibular fibres. A disadvantage of the method is that the exact nature of the units which give rise to the electric charges must remain uncertain; but the records show the same general type of discharge as those found in the frog and seem to give a reasonable picture of most varieties of vestibular activity.
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