Pastras, C.J.; Curthoys, I.S. Vestibular Testing—New Physiological Results for the Optimization of Clinical VEMP Stimuli. Audiol. Res.2023, 13, 910-928.
Pastras, C.J.; Curthoys, I.S. Vestibular Testing—New Physiological Results for the Optimization of Clinical VEMP Stimuli. Audiol. Res. 2023, 13, 910-928.
Pastras, C.J.; Curthoys, I.S. Vestibular Testing—New Physiological Results for the Optimization of Clinical VEMP Stimuli. Audiol. Res.2023, 13, 910-928.
Pastras, C.J.; Curthoys, I.S. Vestibular Testing—New Physiological Results for the Optimization of Clinical VEMP Stimuli. Audiol. Res. 2023, 13, 910-928.
Abstract
Both auditory and vestibular primary afferent neurons can be activated by sound and vibration. This review relates differences between them to the different receptor/synaptic mechanisms of the two systems as shown by indicators of peripheral function – cochlear and vestibular compound action potentials (cCAPs and vCAPs) to click stimulation as recorded in animal studies. Sound and vibration sensitive type 1 receptors at the striola of the utricular macula are enveloped by the unique calyx afferent ending which has three modes of synaptic transmission. Glutamate is the transmitter for both cochlear and vestibular primary afferents, however blocking glutamate transmission has very little effect on vCAPs but greatly reduces cCAPs. We suggest that the ultrafast non-quantal synaptic mechanism called resistive coupling is the cause of the short latency vestibular afferent responses and related results – failure of transmitter blockade, masking, and temporal precision. This “ultrafast” non-quantal transmission is effectively electrical coupling dependent on the membrane potentials of the calyx and the type 1 receptor. The major clinical implication is that decreasing stimulus rise-time increases vCAP response, corresponding to the increased VEMP response in human subjects . Short rise-times are optimum in human clinical VEMP testing, whereas long rise-times are mandatory for audiometric threshold testing.
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