No description available.

No description available.

No description available.

No description available.

Cervical vestibular-evoked myogenic potentials (cVEMPs) are recorded from the sternocleidomastoid muscle using air conduction or bone conduction acoustic stimuli, skull taps, or transmastoid current. The diagnostic usefulness of the cVEMP has been examined for various peripheral and central vestibulopathies. Recent reports indicate that it is possible to record short-latency ocular vestibular-evoked myogenic potentials (oVEMPs) from surface electrodes below the eyes in response to air conduction and bone conduction stimuli. Both methods provide diagnostic information about otolith function. This article provides an overview of each method and highlights the similarities and differences. Several cases are presented to illustrate the relation between the results for cVEMPs and oVEMPs in patients with well-defined audiovestibular disorders.

No description available.

No description available.

Vestibular evoked myogenic potentials (VEMPs) are short-latency electromyograms evoked by high-level acoustic stimuli recorded from surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle. These responses are presumed to originate in the saccule. The purpose of this preliminary report is to provide an overview of our initial experience with the VEMP by describing the responses obtained in five subjects. Click-evoked VEMPs were present at short latencies in two normal-hearing subjects, one patient with profound congenital sensorineural hearing loss, and one patient with a severe sensorineural hearing loss due to Meniere's disease. Additionally, VEMPs were absent in a patient with profound sensorineural hearing loss following removal of a cerebellopontine angle tumor. The amplitude of the VEMP was influenced by the amount of background activity of the SCM muscle, stimulus level, and stimulus frequency. Tone-burst evoked responses showed an inverse relationship between stimulus frequency and response latency. VEMPs may prove to be a reliable technique in the clinical assessment of vestibular function.

Objective: Cervical vestibular evoked myogenic potentials (cVEMPs) are short-latency electromyogram (EMG) evoked by high-level acoustic stimuli recorded from the activated sternocleidomastoid muscle and used to evaluate otolith organ function. The purpose of this study was to investigate the effects of aging on the cVEMP and on the sternocleidomastoid muscle EMG level. Design: A cross-sectional observational study was used to investigate differences in cVEMP and sternocleidomastoid muscle EMG level in a group of 24 younger and 24 older individuals. cVEMPs were recorded during activation of the sternocleidomastoid muscle at target EMG levels ranging from 0 to 90 μV and during maximum voluntary contraction of the sternocleidomastoid muscle. Results: The sternocleidomastoid muscle EMG amplitude increased as a function of target EMG level for both age groups; however, the mean EMG amplitude was greater for the younger group than the older group, and the variability of EMG amplitude was greater for the older group. The EMG amplitude at maximum voluntary contraction ranged from 88 to 279 μV for the younger subjects and from 32 to 230 μV for the older subjects, and the mean EMG amplitude at maximum voluntary contraction was significantly greater for the younger group than the older group. The cVEMP amplitude increased as a function of EMG target level for each age group. Although cVEMP amplitude increased as a function of target EMG level for both groups, the older group exhibited smaller cVEMP amplitudes, overall, compared with the younger group. To separate the influence of EMG level from aging on cVEMP amplitude, only the responses obtained at the 30 μV target EMG level were considered for the statistical analysis because there was no significant difference in EMG level between groups at the 30 μV target level. The mean cVEMP amplitudes at the 30 μV target level were 101 and 51 μV for the younger and older groups, respectively, and a statistical analysis indicated that cVEMP amplitude for the younger group was significantly greater than the older group. Conclusions: The findings suggest that the decrement in cVEMP amplitude is related to both age-related changes in the vestibular system and age-related changes in the sternocleidomastoid muscle.

Ce travail a pour but de décrire les relations réciproques entre prise de perspective et informations vestibulaires. Une étude chez des patients avec un déficit vestibulaire bilatéral ancien et des sujets contrôles a montré que l’ancrage du soi sur le corps et la simulation implicite de la perspective visuo-spatiale d’autrui étaient similaires chez les deux groupes. Ainsi, une perte vestibulaire ancienne n’entraînerait pas de conflits multisensoriels, connus pour évoquer un sentiment de perspective désincarnée chez des patients avec des déficits vestibulaires aigus. Une étude chez des volontaires sains a combiné des stimulations vestibulaires naturelles sur fauteuil rotatoire à des tâches de prise de perspective dans un environnement virtuel embarqué. Les temps de prise de perspective étaient modulés en fonction de la direction de la rotation. Cette influence n’était pas présente pour la rotation mentale d’objets 3D. La contribution vestibulaire canalaire modulerait donc spécifiquement les rotations mentales du point de vue. Enfin, les modulations cognitives du traitement des informations vestibulaires ont été analysées par l’enregistrement de potentiels évoqués myogéniques vestibulaires sur les muscles sternocléidomastoïdiens et trapèzes. L’amplitude des potentiels évoqués était significativement modulée par l’angle séparant le point de vue du participant et celui d’un avatar distant. Nos travaux théoriques et les résultats de cette série d’expériences démontrent la contribution des informations vestibulaires à la prise de perspective visuo-spatiale. / This thesis aims at describing the reciprocal relations between perspective taking and the vestibular system. A study in patients with bilateral vestibular deficits and controls showed that the anchoring of the self to the body and implicit visuo-spatial perspective taking were similar in both groups. Our negative findings offer insight into the multisensory mechanisms of embodiment: only acute peripheral vestibular disorders and neurological disorders in vestibular brain areas may evoke disembodied experiences. A second study, combined natural vestibular stimulation on a rotatory chair with virtual reality to test how vestibular signals are processed to simulate the view point of a distant avatar. While they were rotated, participants tossed a ball to a virtual character from the view point of a distant avatar. Our results showed that participants were faster when their physical body rotated in the same direction as the mental rotation needed to take the avatar's viewpoint. Altogether, these data indicate that vestibular signals have a direction-specific influence on visuo-spatial perspective taking, but not a general effect on mental imagery. Finally, cognitive modulations of vestibular information processing were analyzed by recording vestibular-evoked myogenic potentials on the sternocleidomastoid and trapeze muscles. The amplitude of evoked potentials was significantly modulated by the angle separating the participant’s viewpoint to that of a distant avatar. To conclude, our theoretical work, together with results from this series of experiments, demonstrate the contribution of vestibular information to visuo-spatial perspective taking.