Common Motor Drive Triggers Response of Prime Movers When Two Fingers Simultaneously Respond to a Cue.

Yasutomo Jono,Yasuyuki Iwata,Atsushi Kinoshita,Koichi Hiraoka

doi:10.3390/brainsci11060700

Abstract

This study investigated whether the motor execution process of one finger movement in response to a start cue is influenced by the participation of another finger movement and whether the process of the finger movement is dependent on the movement direction. The participants performed a simple reaction time (RT) task, the abduction or flexion of one (index or little finger) or two fingers (index and little fingers). The RT of the prime mover for the finger abduction was significantly longer than that for the flexion, indicating that the time taken for the motor execution of the finger response is dependent on the movement direction. The RT of the prime mover was prolonged when the abduction of another finger, whose RT was longer than the flexion, was added. This caused closer RTs between the prime movers for a two-finger response compared with the RTs for a one finger response. The absolute difference in the RT between the index and little finger responses became smaller when two fingers responded together compared with one finger response. Those results are well explained by a view that the common motor drive triggers the prime movers when two fingers move together in response to a start cue.

Highlights

To perform the hand movement in daily activity, a complex and cooperative activation of the hand muscles is needed
The corticospinal control is different between the first dorsal interosseous muscle (FDI), which is the prime mover of the index finger movement, and the abductor digiti minimi muscle (ADM), which is the prime mover of the little finger [10,11]
The enslaved response of the FDI induced by the little finger abduction is different from that of the ADM induced by the index finger abduction [40]

Summary

Introduction

To perform the hand movement in daily activity, a complex and cooperative activation of the hand muscles is needed. Such complex activity of the muscles has been thought to be mediated by the multi-finger synergy mechanism that allows a simple control of the muscle activities [1,2,3,4]. The neural mechanism underlying the execution process of the multi-finger movement has not been well understood. The motor execution process of the multi-finger movement was speculated through observing the time taken for the prime movers to respond to a start cue, represented by the reaction time (RT). For the simple RT, orienting to the stimulus is not involved, since the same imperative cue is given at the same locus across the trials

Methods

Results

Discussion

Conclusion