Suppression of the vestibular short-latency evoked potential by electrical stimulation of the central vestibular system (original) (raw)
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The adequate stimulus for mammalian linear vestibular evoked potentials (VsEPs)
2011
Short latency linear vestibular sensory evoked potentials (VsEPs) provide a means to objectively and directly assess the function of gravity receptors in mammals and birds. The importance of this functional measure is illustrated by its use in studies of the genetic basis of vestibular function and disease. Head motion is the stimulus for the VsEP. In the bird, it has been established that neurons mediating the linear VsEP respond collectively to the rate of change in linear acceleration during head movement (i.e. jerk) rather than peak acceleration. The kinematic element of motion responsible for triggering mammalian VsEPs has not been characterized in detail. Here we tested the hypothesis that jerk is the kinematic component of head motion responsible for VsEP characteristics. VsEP amplitudes and latencies changed systematically when peak acceleration level was held constant and jerk level was varied from ∼0.9-4.6 g/ms. In contrast, responses remained relatively constant when kinematic jerk was held constant and peak acceleration was varied from ∼0.9 to 5.5 g in mice and ∼0.44 to 2.75 g in rats. Thus the mammalian VsEP depends on jerk levels and not peak acceleration. We conclude that kinematic jerk is the adequate stimulus for the mammalian VsEP. This sheds light on the behavior of neurons generating the response. The results also provide the basis for standardizing the reporting of stimulus levels, which is key to ensuring that response characteristics reported in the literature by many laboratories can be effectively compared and interpreted.
Observations upon the evoked responses to natural vestibular stimulation
Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section, 1985
Summa~ Repetitive rotational stimuli simulating natural head movements have been applied to the study of the vestibular evoked response in normal subjects and 12 patients with complete loss of vestibular function. Special precautions were taken to eliminate all possible sources of artefacts, in particular, all eye movements were restrained by requiring the subject to fixate upon a target light attached to the rotating chair throughout the course of the test. With a stimulus of 2 sec duration the typical response took the form of a slow negative wave with a mean peak amplitude of approximately 24/~V and maximally recorded from the vertex. It was characteristically absent in the patient group. Occasionally, both in normal subjects and patients it was preceded by a long latency complex thought to be non-vestibular in origin. Tests carried out both in total darkness and in the light show a statistically significant increase in the potential in the latter condition indicating an influence of the optokinetic effect exerted by the visual surround. Further studies have explored the phase changes brought about by varying the amplitude and duration of the stimulus. These have revealed certain parallels in the results of recent animal experimental studies.
Reviewing the Role of the Efferent Vestibular System in Motor and Vestibular Circuits
Frontiers in physiology, 2017
Efferent circuits within the nervous system carry nerve impulses from the central nervous system to sensory end organs. Vestibular efferents originate in the brainstem and terminate on hair cells and primary afferent fibers in the semicircular canals and otolith organs within the inner ear. The function of this efferent vestibular system (EVS) in vestibular and motor coordination though, has proven difficult to determine, and remains under debate. We consider current literature that implicate corollary discharge from the spinal cord through the efferent vestibular nucleus (EVN), and hint at a potential role in overall vestibular plasticity and compensation. Hypotheses range from differentiating between passive and active movements at the level of vestibular afferents, to EVS activation under specific behavioral and environmental contexts such as arousal, predation, and locomotion. In this review, we summarize current knowledge of EVS circuitry, its effects on vestibular hair cell an...
Frontiers in neurology, 2017
Galvanic vestibular stimulation (GVS) delivered as zero-mean current noise (noisy GVS) has been shown to improve static and dynamic postural stability probably by enhancing vestibular information. The purpose of this study was to examine the effect of an imperceptible level noisy GVS on ocular vestibular-evoked myogenic potentials (oVEMPs) in response to bone-conducted vibration (BCV). oVEMPs to BCV were measured during the application of white noise GVS with an amplitude ranging from 0 to 300 µA [in root mean square (RMS)] in 20 healthy subjects. Artifacts in the oVEMPs caused by GVS were reduced by inverting the waveforms of noisy GVS in the later half of the stimulus from the one in the early half. We examined the amplitudes of N1 and N1-P1 and their latencies. Noisy GVS significantly increased the N1 and N1-P1 amplitudes (p < 0.05) whereas it had no significant effects on N1 or P1 latencies (p > 0.05). Noisy GVS had facilitatory effects in 79% of ears. The amplitude of the...
Experimental Brain Research, 2011
Electrical vestibular stimulation produces biphasic responses in muscles maintaining balance. The two components of these muscle responses (termed the short latency and medium latency components) are believed to be independent and elicited by vestibular stimuli of different frequencies. We tested these hypotheses by determining (a) if frequency-specific stimulation protocols could evoke independently the short and medium latency responses and (b) whether these two components are triggered by distinct brain regions with a fixed time delay, interacting around 10 Hz. First, subjects were provided 10-25 Hz, 0-10 Hz, and 0-25 Hz vestibular stimuli to selectively modulate the short latency, medium latency, or both components of the response; and second, they were provided twenty sinusoidal stimuli from 1 to 20 Hz with a 0-20 Hz control trial, designed to determine whether an interaction between the short and medium latency responses occurs at a specific stimulation frequency. Both the 0-10 Hz and 10-25 Hz vestibular stimuli elicited multiphasic waveforms, suggesting the short and medium latency components were not modulated independently by the frequency-specific stimuli. Sinusoidal vestibular stimuli evoked responses at the stimulated frequency but no evidence of a reflex component interaction was observed. Instead, summation of the responses evoked by each of the sinusoidal stimuli resembled the biphasic response to broad bandwidth stimuli. Due to the lack of interaction and linear contribution of all stimulus frequencies to both the short and medium latency responses, the present results support the use of broad bandwidth electrical vestibular signal for physiological or clinical testing.
Motion sickness (MS) or kinetosis is a sensory-motor dys function caused by a mismatch between the visual ly perceived movement and its neural integration with the pro-prioceptive and vestibular system 1,2. As a result of this mis-match balance, gait and locomotion anomalies appear, which worsens the disabling dysautonomia that such mismatch originates 1,3-5. These neural disorders debut during land, marine , and aerospace motion, among others conditions 1,2. MS can be developed in up to 39% of airplane pilot students 6,7. Of remark, kinetosis is present in up to 91% of the human factors involved in aerial accidents 3. Despite repeated exposure to environmental conditions simulating kinetosis, MS appears ABSTRACT Motion sickness or kinetosis is the result of the abnormal neural output originated by visual, proprioceptive and vestibular mismatch, which reverses once the dysfunctional sensory information becomes coherent. The space adaptation syndrome or space sickness relates to motion sickness; it is considered to be due to yaw, pith, and roll coordinates mismatch. Several behavioural and pharmacological measures have been proposed to control these vestibular-associated movement disorders with no success. Galvanic vestibular stimulation has the potential of up-regulating disturbed sensory-motor mismatch originated by kinetosis and space sickness by modulating the GABA-related ion channels neural transmission in the inner ear. It improves the signal-to-noise ratio of the afferent proprioceptive volleys, which would ultimately modulate the motor output restoring the disordered gait, balance and human locomotion due to kinetosis, as well as the spatial disorienta-tion generated by gravity transition. RESUMO A cinetose ou doença do movimento resulta de uma resposta neural anormal originada do desequilíbrio entre estímulos visuais, propriocep-tivos e vestibulares, que melhora quando esse desequilíbrio é corrigido. A síndrome de adaptação espacial ou doença do espaço está rela-cionada à doença do movimento e é desencadeada por mudanças bruscas de direção, inclinação e rotação da cabeça. Têm sido propostas várias medidas comportamentais e farmacológicas para controlar esses transtornos do movimento associados com o sistema vestibular, mas sem sucesso. A estimulação galvânica vestibular pode regular o desequilíbrio sensitivo-motor causado pela cinetose e pela doença do espaço modulando os canais iônicos GABA, relacionados à transmissão de impulsos nervosos no ouvido interno. Essa estimulação melhora a relação sinal-ruído dos impulsos proprioceptivos que acabam modulando a resposta motora, restabelecendo o equilíbrio e a marcha, re-cuperando a desorientação espacial causada pelos diversos gradientes de gravidade. Palavras-chave: enjoo de movimento, orientação aeroespacial, estimulação galvânica vestibular, distúrbios do movimento, síndrome de adaptação aeroespacial, GABA.
Galvanic and acoustic vestibular stimulation activate different populations of vestibular afferents
Clinical Neurophysiology, 2003
Objective: To deduce whether similar or distinct populations of vestibular afferents are activated by acoustic and galvanic vestibular stimulation by comparing the effectiveness of 'matched' stimuli in eliciting vestibulospinal reflexes. Methods: Twelve subjects (5 men, 7 women) underwent individual 'matching' of 2 ms tone burst and galvanic stimuli, using vestibulocollic reflexes so that corrected reflex amplitudes to tone burst and galvanic stimuli were within 10% of each other. These same intensities were then administered using 20 ms durations to determine whether they were equally effective in evoking vestibulospinal responses. Results: Corrected reflex amplitudes for vestibulocollic responses to tone burst and galvanic stimulation were not significantly different for the right (P ¼ 0:45) or left (P ¼ 0:68) sides. All subjects had vestibulospinal responses to galvanic stimulation (average intensity 4.0 mA for both sides). The short latency (SL) and medium latency (ML) components of the vestibulospinal reflexes were larger after galvanic compared to tone burst stimulation in 11 of 12 subjects (P , 0:01). Conclusions: Despite evoking equal-sized vestibulocollic reflexes, there was a clear dissociation between the magnitude of tone burst and galvanic-induced vestibulospinal reflexes. Galvanic stimulation evoked SL and ML reflexes in all subjects. Tone burst stimuli evoked only small SL reflexes and, in most cases, no ML reflexes. Acoustically-evoked vestibulocollic reflexes are likely to be due to saccular excitation. The limited effectiveness of longer tone burst stimuli to evoke ML vestibulospinal reflexes suggests that saccular afferents have, at most, only a minor role in the production of these reflexes. We conclude that galvanic stimulation is more effective in eliciting vestibulospinal reflexes than tone burst stimulation, and that the two methods activate different populations of vestibular afferents.
Motion sickness (MS) or kinetosis is a sensory-motor dys function caused by a mismatch between the visual ly perceived movement and its neural integration with the proprioceptive and vestibular system 1,2 . As a result of this mismatch balance, gait and locomotion anomalies appear, which worsens the disabling dysautonomia that such mismatch originates 1,3-5 . These neural disorders debut during land, marine, and aerospace motion, among others conditions 1,2 . MS can be developed in up to 39% of airplane pilot students 6,7 . Of remark, kinetosis is present in up to 91% of the human factors involved in aerial accidents 3 . Despite repeated exposure to environmental conditions simulating kinetosis, MS appears ABSTRACT Motion sickness or kinetosis is the result of the abnormal neural output originated by visual, proprioceptive and vestibular mismatch, which reverses once the dysfunctional sensory information becomes coherent. The space adaptation syndrome or space sickness relates to motion sickness; it is considered to be due to yaw, pith, and roll coordinates mismatch. Several behavioural and pharmacological measures have been proposed to control these vestibular-associated movement disorders with no success. Galvanic vestibular stimulation has the potential of up-regulating disturbed sensory-motor mismatch originated by kinetosis and space sickness by modulating the GABA-related ion channels neural transmission in the inner ear. It improves the signal-to-noise ratio of the afferent proprioceptive volleys, which would ultimately modulate the motor output restoring the disordered gait, balance and human locomotion due to kinetosis, as well as the spatial disorientation generated by gravity transition.
Characterization of the Electrically Evoked Compound Action Potential of the Vestibular Nerve
Otology & Neurotology, 2011
Objective-We recorded intra-operative and post-operative electrically-evoked compound action potentials (ECAPs) in rhesus monkeys implanted with a vestibular neurostimulator. The objectives were to correlate the generation of slow-phase nystagmus or eye twitches induced by electrical stimulation of the implanted semicircular canal with the presence or absence of the vestibular ECAP responses, and to assess the effectiveness of ECAP monitoring during surgery to guide surgical insertion of electrode arrays into the canals. Design-Four rhesus monkeys (a total of seven canals) were implanted with a vestibular neurostimulator modified from the Nucleus Freedom™ cochlear implant. ECAP recordings were obtained during surgery or at various intervals post-surgery using the Neural Response Telemetry™ feature of the clinical Custom Sound EP™ software. Eye movements during electrical stimulation of individual canals were recorded with a scleral search coil system in the same animals. Results-Measurable vestibular ECAPs were observed intra-operatively or post-operatively in three implanted animals. Robust and sustained ECAPs were obtained in three monkeys at the test intervals of 0, 7, or >100 days post implantation surgery. In all three animals, stimulation with electrical pulse trains produced measurable eye movements in a direction consistent with the vestibulo-ocular reflex from the implanted semicircular canal. In contrast, electrically-evoked eye movements could not be measured in three of the seven implanted canals none of which produced distinct vestibular ECAPs. In two animals, ECAP waveforms were systematically monitored during surgery and the procedure proved crucial to the success of vestibular implantation. Conclusions-Vestibular ECAPs exhibit similar morphology and growth characteristics to cochlear ECAPs from human cochlear implant patients. The ECAP measure is well correlated with the functional activation of eye movements by electrical stimulation post implantation surgery. The intra-operative ECAP recording technique is an efficient tool to guide the placement of electrode array into the semicircular canals.