Proprioceptive consequences of tendon vibration during movement.
Cordo, P., V. S. Gurfinkel, L. Bevan and G. K. Kerr.
.Robert S. Dow Neurological Sciences Institute, Legacy Good Samaritan
Hospital and Medical Center and Department of Physiology, Oregon Health
Sciences University, Institute for Information Transmission Problems, Russian
Academy of Sciences, School of Dentistry, Oregon Health Sciences University,
School of Human Movement Studies, Queensland University of Technology
APStracts 2:0176N, 1995.
SUMMARY AND CONCLUSIONS
1. Previous studies have used tendon vibration to investigate kinesthetic
illusions in the isometric limb and end-point control in the moving limb.
These previous studies have shown that vibration distorts the perceptions of
static joint angle and movement, and it causes systematic errors in the end-
point of movement. In this paper, we describe the effects of tendon vibration
during movement while human subjects performed a proprioceptively coordinated
motor task. In an earlier study, we showed that the central nervous system
(CNS) coordinates this motor taskÄa movement sequenceÄwith proprioceptive
information related to the dynamic position and velocity of the limb. 2. When
performing this movement sequence, each subject sat at a table and opened the
right hand as the right elbow was passively rotated in the extension direction
through a prescribed target angle. Vision of the arm was prevented, and the
movement velocity was changed randomly from trial to trial, leaving
proprioception as the only useful source of kinematic information with which
to perform the task. 3. In randomly occurring trials, vibration was applied to
the tendon of the biceps brachii, a muscle that lengthens during elbow
extension. In some experiments, the timing of tendon vibration was varied with
respect to the onset of elbow rotation, and in other experiments, the
frequency of vibration was varied. In each experiment, we compared the
accuracy of the subject's response (i.e., the elbow angle at which they opened
the hand) in trials with tendon vibration to the accuracy in trials without
tendon vibration. 4. The effect of tendon vibration depended on the frequency
of vibration. When the biceps tendon was vibrated at 20 Hz, subjects opened
the hand after the elbow passed through ("overshooting") the target angle.
Overshooting is consistent with an underestimate of the actual displacement or
velocity of the elbow. Vibration at 30 Hz had little or no effect on the elbow
angle at hand-opening. Vibration at 40 Hz caused subjects to open the hand
before the elbow reached ("undershooting") the target angle. Undershooting is
consistent with an overestimate of the actual displacement or velocity of the
elbow. The size of the error depended on the velocity of the passively imposed
elbow rotation. 5. The effect of tendon vibration also depended on the timing
of vibration. If 40 Hz vibration began at the onset of movement, the subject
undershot the target. If 40 Hz vibration started 5 s before movement onset and
continued throughout the movement, the undershoot error increased in
magnitude. However, if 40 Hz vibration started 5 s before and then stopped at
movement onset, the subject overshot the target. When vibration was shut off
during movement, a transition occurred from an overshooting error to an
undershooting error at a time that depended on the velocity of elbow rotation.
6. In a separate experiment, subjects were instructed to match either the
perceived dynamic position or the perceived velocity of rotation imposed on
the right elbow by actively rotating the left elbow. In both matching tasks,
tendon vibration produced oppositely directed errors depending on the
frequency of vibration. Vibration at 20 Hz produced a perception of decreased
elbow velocity and a bias in dynamic position in the flexion direction, and
vibration at 40 Hz produced the opposite perceptions. 7. We conclude that
muscle spindle afferents, which are activated by tendon vibration, are an
important source of the dynamic position and velocity information that the CNS
uses to coordinate this movement sequence task. The observed effects of
vibration timing and frequency suggest that perceptual changes evoked by
vibration cannot be explained by the simple summation of sensory input evoked
by movement and by vibration. Rather, the bias in perception produced by
vibration appears to be related to the difference between vibration- and
movement-evoked activity in muscle spindle afferents.
Received 5 December 1994; accepted in final form 5 June 1995.
APS Manuscript Number J759-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.