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| Research article summary (published 30 Jul 2003): |
EMG responses evoked by the termination of galvanic (DC) vestibular stimulation: 'off-responses'.
Full Abstract
OBJECTIVE:
Vestibular responses in soleus electromyography (EMG) evoked by the sudden onset of galvanic (DC) stimulation ('on-responses') have been described in detail previously. The aim of the present study was to describe responses in soleus triggered by the termination of galvanic stimulation ('off-responses').
METHODS:
In 10 healthy human subjects, we studied responses to transmastoid (bilateral) stimuli of 200 ms and 2 s average duration and 3 or 4 mA intensity. We obtained both on- and off-responses using the same raw data. EMG activity was recorded onto tape while current pulses of systematically varying duration were delivered. Averaged on-responses were obtained by triggering from the beginning of the current pulses. Averaged off-responses were obtained by triggering from the termination of the current pulses.
RESULTS:
Short-latency (SL) and medium latency (ML) off-responses were both obtained in all but one study. The SL and the ML components of the off-responses were present and had similar latencies and amplitudes, but opposite excitability, to the on-responses obtained with the same stimuli.
CONCLUSIONS:
Off-responses to galvanic vestibular stimulation can be recorded from soleus EMG. Our findings imply that vestibular SL and ML reflex responses in the legs are dependent on the change in the rate of vestibular nerve discharge, not its absolute level. Both on- and off-responses have properties appropriate to a role in maintaining body stability.
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Author information
Author/s: Watson, S R D (SR); Welgampola, M S (MS); Colebatch, J G (JG);
Affiliation: Institute of Neurological Sciences, Sydney, NSW, Australia.
Journal and publication information
Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't
Journal: Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology (Clin Neurophysiol), published in Netherlands. (Language: eng)
Reference: 2003-Aug; vol 114 (issue 8) : pp 1456-61
Dates: Created 2003/07/30; Completed 2003/10/01; Revised 2008/09/10;
PMID: 12888028, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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