Format

Send to

Choose Destination
Exp Brain Res. 2019 Dec;237(12):3485-3492. doi: 10.1007/s00221-019-05693-x. Epub 2019 Nov 18.

Neural mechanism of selective finger movement independent of synergistic movement.

Author information

1
Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-gun, Ibaraki, Japan. aoyamato@ipu.ac.jp.
2
Department of Rehabilitation Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, Japan.
3
Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-gun, Ibaraki, Japan.
4
Center for Medical Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-gun, Ibaraki, Japan.

Abstract

Muscle synergy is important for simplifying functional movement, which constitutes spatiotemporal patterns of activity across muscles. To execute selective finger movements that are independent of synergistic movement patterns, we hypothesized that inhibitory neural activity is necessary to suppress enslaved finger movement caused by synergist muscles. To test this hypothesis, we focused on a pair of synergist muscles used in the hand opening movement, namely the index finger abductor and little finger abductor (abductor digiti minimi; ADM), and examined whether inhibitory neural activity in ADM occurs during selective index finger abduction/adduction movements and/or its imagery using transcranial magnetic stimulation and F-wave analysis. During the index finger adduction movement, background EMG activity, F-wave persistence, and motor evoked potential (MEP) amplitude in ADM were elevated. However, during the index finger abduction movement, ADM MEP amplitude remained unchanged despite increased background EMG activity and F-wave persistence. These results suggest that increased spinal excitability in ADM is counterbalanced by cortical-mediated inhibition only during selective index finger abduction movement. This assumption was further supported by the results of motor imagery experiments. Although F-wave persistence in ADM increased only during motor imagery of index finger abduction, ADM MEP amplitude during motor imagery of index finger abduction was significantly lower than that during adduction. Overall, our findings indicate that cortical-mediated inhibition contributes to the execution of selective finger movements that are independent of synergistic hand movement patterns.

KEYWORDS:

F-wave; Hand synergy; Inhibitory neural activity; Selective finger movement; Transcranial magnetic stimulation

PMID:
31741000
DOI:
10.1007/s00221-019-05693-x

Supplemental Content

Full text links

Icon for Springer
Loading ...
Support Center