Cortical vestibular representation in the superior temporal gyrus

We present the unique case of a patient with a circumscribed solitary cerebral metastasis of a malignant melanoma extending from the medial part of the superior temporal gyrus to the lower part of the 1st long insular gyrus causing gait and stance instability and an ipsiversive tilt of the subjective visual vertical. Oculomotor disorders could not be detected. We suggest that the superior temporal gyrus is likely to be involved in spatial orientation presumably using otolithic information.     

Cortical representation of the vestibular system as evidenced by brain electrical activity mapping of vestibular late evoked potentials

We examined the space and temporal distributions of the rotatory evoked brain electrical activity patterns (brain electrical activity mapping of vestibular evoked potentials [VestEP]) in humans. We performed a longitudinal scalp line analysis, transversal line analysis, and clockwise/counterclockwise rotation analysis of the VestEP principal components in 75 healthy persons aged 22 to 30 years (mean: 25.8). We found that the shortest VestEP latencies and the highest amplitudes were registered in a relatively distinct cortical area that is covered by the transversal electrode line T3-C3-Cz-C4-T4, in accordance with the 10/20 international electrode scheme. This area corresponds to the posterior part of the frontal lobe (Brodmann's area 4, the primary motor field of the isocortex) and the anterior parts of the cerebral parietal lobe (the gyrus postcentralis, which corresponds to the primary somatosensory fields, Brodmann's areas 1, 2, and 3). In this article, we discuss a method of investigation that exhibits the VestEPs, and we review one normal case and three typical cases of pathologic VestEPs.     

Cervical and vestibular afferent control of oculomotor response in man.

Oculomotor response in the absence of vision has been compared in a group of 12 normal humans in two experimental conditions testing (a) the vestibulocular reflex by whole-body oscillation on a turntable, and (b) the cervico-ocular reflex by oscillation of the body with the head held stationary. The stimulus was a sinusoidal oscillation (peak angular velocity +/- 50 degrees/sec) at frequencies between 0.2 and 1.3 Hz. The slow-phase eye movements of the vestibulo-ocular response were compensatory for head movement and showed a mean gain of 0.54--0.90, increasing with frequency. The cervicoocular response was found to be very variable. The slow-phase eye movements were of low velocity (mean gain 0.05) and did not generally compensate for body movement. During neck torsion, some subjects exhibited large overall eye deviations composed of both slow and fast phase eye movements.     

On the interaction of vestibular and optokinetic nystagmus in man.

The interaction of vestibular and optokinetic nystagmus (OKN) was investigated by applying periods of ipsi- and contradirectional optokinetic stimulation during perand postrotatory vestibular nystagmus in healthy humans. Slow phase velocity and cumulative eye displacement of OKN was enhanced by vestibular nystagmus beating in the same direction of decreased by contradirectional vestibular nystagmus. A distinct correlation between the intensity of vestibular stimulation and the modification of OKN could be demonstrated by averaging the responses obtained in different subjects. On the other hand there was also a modification (enhancement or decrease) of vestibular nystagmus slow phase velocity by preceding OKN. Considering the intensity of these modifications, large interindividual differences were observed.     

Vertical vestibuloocular reflexes in affection of central parts of vestibular system (communication III)

Vertical vestibuloocular reflexes (VVOR) were examined in 45 patients with multiple sclerosis. It is proposed to study VVOR basing on stimulation of the vertical semicircular labirynthine canals with active sagittal nodding of the head. Central lesion of the vestibular system is characterized by VVOR hyperreactivity, total failure of VVOR suppression by glance, two types of VVOR domination (typical--up and atypical--down), interocular asymmetry (dissociated nystagmus).     

Adrenergic innervation of the eighth nerve and vestibular end organs in man

Summary Fluorescence microscopy was used to examine the adrenergic, bloodvessel-independent innervation of the 8th nerve and inner ear specimens in patients with otoneurological diseases. Specifically fluorescent adrenergic axons were scantily seen among the myelinated nerve fibers in the 8th nerve and in the subepithelial regions of the end organs but not in the endolymphatic sac.This work was supported by a grant from the Signe and Ane Gyllenberg Foundation     

Evidence for a vestibular input contributing to dynamic head stabilization in man

Horizontal head movements in response to unpredictable horizontal oscillations of the trunk were studied in 6 patients lacking vestibular function and in 6 normal subjects. In order to obtain compensatory (i.e. stabilizing with respect to earth) head movements, all subjects were required to look at an earth-fixed target, using their eyes and head. The turning points (maxima and minima) were determined from head and trunk position records. It was found that normal subjects reversed the direction of head movements in advance of trunk movements (mean lead = 82 ms) whereas the patients reversed head direction after the trunk (mean lag = 169 ms). The coherence function between head and trunk movements, measured with a spectral analyser in an additional labyrinthineless patient, was considerably lower than in normal controls. It is concluded that patients lacking vestibular function have impaired stabilization of the head in space, which can be taken as indirect evidence of the existence of active dynamic vestibulo-collic reflex (VCR) mechanisms in normal man. The lead found in normal subjects, notwithstanding the unpredictability of the stimuli, may reflect the detection of early acceleration signals by the vestibular apparatus to organize compensatory head movements.