Differential neural coordination of bilateral hand and finger movements

Abstract

Cooperative hand movements (e.g., opening a bottle) require a close coordination of the hands. This is reflected in a neural coupling between the two sides. The aim of this study was to investigate in how far neural coupling is present not only during bilateral hand but also during bilateral finger movements. For this purpose unilateral mechanical and electrical nerve stimuli were delivered during bilateral sequentially and synchronously performed finger movements on a keyboard and, for comparison, during bilateral hand flexion movements. Electromyographic (EMG) activity and reflex responses in forearm flexor and extensor muscles of both sides were recorded and analyzed. Confounding EMG activity related to hand movements during the finger task was limited by wrist fixating braces. During the hand flexion task, complex reflex responses appeared in the forearm muscles of both sides to unilateral stimulation of the ulnar nerve (mean latency 57 ms), reflecting neural coupling between the two hands. In contrast, during the bilateral finger movement task, unilateral electrical nerve or mechanical stimulation of the right index finger was followed by dominant ipsilateral reflex responses (latency 45 and 58 ms, respectively). The results indicate that in contrast to the coupled hand movements, finger movements may not be coupled but can move independently on each side. Functionally this makes sense because during most activities of daily living, a close cooperation of the hands but not of individual fingers is needed. This independence of individual finger movements may rely on strong, specific, contralateral cortico‐motoneuronal control.

The impact of lesion side on bilateral upper limb coordination after stroke

“…For example, electrical stimulation to forearm muscles on one limb during bilateral hand movement resulted in muscular responses in both limbs, whereas stimulation to one finger during bilateral finger movement resulted in responses only in the stimulated finger. Moreover, recovery outcomes for proximal muscle movements are usually better than that for distal muscles following cortico-spinal tract damage [ 57 ]. Therefore there seem to be differences in cortico-muscular coupling and corticospinal contributions between proximal and distal movement control.…”

Neural coordination of bilateral power and precision finger movements

“…F I G U R E 2 Illustration of the experiments performed in the study of Caldelari et al (2020). The experiment consisted of two tasks.…”

“…The second task (c) consisted of bilateral hand flexion movements while holding dumbbells (load 0.5 kg). Electrical stimuli to the right ulnar nerve were randomly applied during the rising phase of the hand movements (Caldelari, Lemon and Dietz, 2020) | DIETZ…”

“…In a recent electrophysiological study, neural control was compared between bilateral finger and bilateral hand movements (Caldelari et al, 2020; Figure 2). A differential behavior of reflexes function between hand and finger movements was observed although similar visual and proprioceptive feedback was provided in both tasks.…”