Model-based prediction of fusimotor activity during active wrist movements

Bernard Grandjean,Marc A Maier

doi:10.1186/1471-2202-14-s1-o16

Abstract

Muscle spindles, whose activity is determined by muscle length changes and by fusimotor drive (i.e. γ-drive), provide critical information about movement position and velocity [1]. However, task-dependent fusimotor drive remains largely unknown [2], since no fusimotor neurons have ever been recorded during active, voluntary upper limb movements, whether in animals nor in humans. So far an estimation of γ-drive could only be obtained through an indirect inference of fusimotor activity from observed muscle spindle activity. Our aim was to model the effect of γ-drive on muscle spindles and to simulate voluntary wrist movements for which the spindle responses are empirically known.

Highlights

Muscle spindles, whose activity is determined by muscle length changes and by fusimotor drive (i.e. g-drive), provide critical information about movement position and velocity [1]
Our simulations suggest that (i) empirically observed muscle spindle activity profiles can to a large part be explained by a strongly task-dependent g-drive (Figure 1B), (ii) observed differences between individual muscle spindle response profiles can be explained by a corresponding variability in the g-drive (Figure 1B), and (iii) observed phase advance of spindle responses can to a large part be explained by appropriate g-drive
Our simulation predicts that g-drive is strongly modulated and task-dependent and that appropriate g-drive can explain many empirically observed aspects of group Ia and II muscle spindle responses during active movements

Summary

Introduction

Muscle spindles, whose activity is determined by muscle length changes and by fusimotor drive (i.e. g-drive), provide critical information about movement position and velocity [1]. Task-dependent fusimotor drive remains largely unknown [2], since no fusimotor neurons have ever been recorded during active, voluntary upper limb movements, whether in animals nor in humans. An estimation of g-drive could only be obtained through an indirect inference of fusimotor activity from observed muscle spindle activity. Our aim was to model the effect of g-drive on muscle spindles and to simulate voluntary wrist movements for which the spindle responses are empirically known

Methods

Results

Conclusion

Prochazka A