Antagonist motor responses correlate with kinesthetic illusions induced by tendon vibration |
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Authors: | S Calvin-Figuière Patricia Romaiguère Jean-Claude Gilhodes Jean-Pierre Roll |
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Institution: | Laboratoire de Neurobiologie Humaine, UMR 6562, CNRS-Université de Provence, Centre de Saint-Jér?me, Avenue Escadrille Normandie-Niemen, F-13397 Marseille cedex 20, France e-mail: rc@newsup.univ-mrs.fr Tel.: +33-4-91-28-88-98, Fax: +33-4-91-28-86-69, FR
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Abstract: | In humans, vibration applied to muscle tendons evokes illusory sensations of movement that are usually associated with an
excitatory tonic response in muscles antagonistic to those vibrated (antagonist vibratory response or AVR). The aim of the
present study was to investigate the neurophysiological mechanisms underlying such a motor response. For that purpose, we
analyzed the relationships between the parameters of the tendon vibration (anatomical site and frequency) and those of the
illusory movement perceived (direction and velocity), as well as the temporal, spatial, and quantitative characteristics of
the corresponding AVRs (i.e., surface EMG, motor unit firing rates and activation latencies). Analogies were supposed between
the characteristics of AVRs and voluntary contractions. The parameters of the AVR were thus compared with those of a voluntary
contraction with similar temporal and mechanical characteristics, involving the same muscle groups as those activated by vibration.
Wrist flexor muscles were vibrated either separately or simultaneously with wrist extensor muscles at frequencies between
30 and 80 Hz. The illusory movement sensations were quantified through contralateral hand-tracking movements. Electromyographic
activity from the extensor carpi radialis muscles was recorded with surface and intramuscular microelectrodes. The results
showed that vibration of the wrist flexor muscle group induced both a kinesthetic illusion of wrist extension and a motor
response in the extensor carpi radialis muscles. Combined vibration of the two antagonistic muscle groups at the same frequency
evoked neither kinesthetic illusion nor motor activity. In addition, vibrating the same two antagonistic muscle groups at
different frequencies induced both a kinesthetic illusion and a motor response in the muscle vibrated at the lowest frequency.
The surface EMG amplitude of the extensor carpi radialis as well as the motor unit activation latency and discharge frequency
were clearly correlated to the parameters of the illusory movement evoked by the vibration. Indeed, the faster the illusory
sensation of movement, the greater the surface EMG in these muscles during the AVRs and the sooner and the more intense the
activation of the motor units of the wrist extensor muscles. Moreover, comparison of the AVR with voluntary contraction showed
that all parameters were highly similar. Mainly slow motor units were recruited during the AVR and during its voluntary reproduction.
That the AVR is observed only when a kinesthetic illusion is evoked, together with the similarities between voluntary contractions
and AVRs, suggests that this vibration-induced motor response may result from a perceptual-to-motor transformation of proprioceptive
information, rather than from spinal reflex mechanisms.
Received: 21 July 1997 / Accepted: 11 August 1998 |
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Keywords: | Vibration-induced kinesthetic illusions Antagonist vibratory response Motor units Wrist extensor muscles Human Microelectromyography |
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