Short and medium latency muscle responses evoked by electrical vestibular stimulation are a composite of all stimulus frequencies |
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Authors: | Christopher J Dakin John Timothy Inglis Jean-Sébastien Blouin |
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Institution: | (1) School of Human Kinetics, University of British Columbia, 210-6081 University Boul., Vancouver, BC, V6T1Z1, Canada;(2) Brain Research Center, University of British Columbia, Vancouver, BC, Canada;(3) International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada |
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Abstract: | 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. |
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