Connectivity of neural signals to the primary motor area during preparatory periods for movement following external and internal cues

Abstract

Purpose

We investigated the connectivity of neural signals from movement-related cortical areas to the primary motor area (M1) in the hemisphere contralateral to the movement side during the period of movement-related magnetic fields before movement.

Materials and methods

Participants were 13 healthy adults, and nerual signals were recorded using magnetoencephalography. Spontaneous extension of the right wrist was performed at the participant’s own pace and following a visual cue in internal (IC) and external (EC) cue tasks. The connectivity of neural signals to M1 from each movement-related motor area was assessed by Granger causality analysis (GCA). The GCA was performed on the neural activity elicited in a frequency band between 7.8 and 46.9 Hz during the pre-movement periods, which occurred durng the readiness field (RF) and the negative slope prime (NSp). F-values, as connectivity values obtained by GCA, were compared between the EC and IC cue tasks.

Results

For NSp periods, the connectivity of neural signals from the left superior frontal area (SF-L) to M1 was dominant in the IC task, whereas that from the left superior parietal area (SP-L) to M1 was dominant in the EC task. The F value in the GCA from SP-L to M1 was greater in the EC task during RF than in the IC task during equivalent periods.

Conslusions

In the present study, there were differences in the connectivity of neural signals to M1 between IC and EC tasks. The present results suggested that the pattern of pre-movement neural activity that resulted in a movement was not uniform but differed between movement tasks just before the movement.

HIGHLIGHTS

• Movement-related cortical magnetic fields were assessed with Granger causality analysis

• Connectivity of neural signals to M1 was different between internal and external cue tasks.

• Connectivity of neural signals from the frontal area was dominant to M1 in the internal cue task.

• Connectivity of neural signals to M1 from the parietal area was observed in the external cue task.

Keywords:

• Readiness potential
• causal analysis
• MEG

Acknowledgement

This work was financially supported by JST SPRING, grant number JPMJSP2125. The first author would like to take this opportunity to thank the ‘Interdisciplinary Frontier Next-Generation Researcher Program of the Tokai Higher Education and Research System’.

Disclosure statement

No potential conflict of interest was reported by the authors.