Independent effects of simultaneous inputs from the saccule and lateral semicircular canal. Evaluation using VEMPs.
OBJECTIVE
To determine the effects of stimulation of bilateral lateral semicircular canals (LSCCs) by accelerated rotation and caloric stimulation of unilateral LSCC on vestibular evoked myogenic potentials (VEMPs) in healthy volunteers.


METHODS
In experiment 1, VEMPs were recorded while subjects (n = 11) were seated in a rotational chair and angular acceleration around the earth-vertical axis was provided. Amplitudes of p13-n23 were corrected using background muscle activities. In experiment 2, subjects (n = 8) in the semilateral position kept the LSCC in the vertical position and activated the sternocleidomastoid muscle by twisting the neck. After irrigating the external auditory canal with ice water, VEMPs were recorded on the irrigated side. In experiment 3, the same setting as experiment 2 was applied (n = 6), and hot water of 44 degrees C was used for irrigation.


RESULTS
There were no significant differences in latencies of p13 or n23, and in corrected amplitudes by either rotatory or caloric stimulation.


CONCLUSIONS
Simultaneous stimulation of LSCCs has little effect on VEMPs.


CONCLUSIONS
No functional interaction between the saccule and LSCC was detected in VEMPs, although convergence of semicircular canal and otolith nerve inputs onto single vestibular nucleus neurons has been demonstrated electrophysiologically in animal experiments.
Karino
Shotaro
S
Department of Otolaryngology Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. karinos-tky@umin.ac.jp
Ito
Ken
K
Ochiai
Atsushi
A
Murofushi
Toshihisa
T
D000328:Adult; D002150:Caloric Tests; D004525:Efferent Pathways / Q000502:physiology*; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009334:Neck Muscles / Q000294:innervation / Q000502:physiology*; D010812:Physical Stimulation; D004856:Postural Balance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012018:Reflex / Q000502:physiology; D012399:Rotation; D012444:Saccule and Utricle / Q000502:physiology*; D012665:Semicircular Canals / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology; D014725:Vestibular Nerve / Q000502:physiology; D014726:Vestibular Nuclei / Q000502:physiology*