Motor control in reaction-time vs self-paced movement : MEG study on movement-related cortical fields

Abstract

Hautasaari, P. 2017. Motor control in reaction-time vs self-paced movement - MEG study on movement-related cortical fields. Sport and Exercise Medicine, Unit of Health Sciences, Faculty of Sport and Health Sciences, University of Jyväskylä, Master’s Thesis in Sport and Exercise Medicine, 34 pages, 2 appendices.

Motor control system in human neural network consists complex coordinated function between different brain areas. In the cortical level supplementary motor area, premotor, primary motor and primary sensory cortices provide major contribution to movement control. Magnetoencephalography (MEG) is a non-invasive brain imaging method measuring the magnetic fields originating from neuronal activity during, e.g. voluntary movement. Movement-related cortical fields (MRCF) comprise of brain activation before, during and after voluntary movement and these fields can be measured with MEG. The purpose of this study was to investigate possible differences between reaction-time and self-paced voluntary movement.

In this study, 18 healthy, right-handed individuals (aged 18-40 years) were measured with MEG. The participants performed voluntary index finger abductions under two conditions. In the first condition the movement was performed self-paced every 4-6 seconds and in the second condition as reaction-time movement after brief electrical stimulus induced in the dorsum of the hand randomly every 4-6 seconds. Muscle activity was measured with electromyography (EMG) and the MRCF was obtained by averaging the MEG recording in relation to onset of muscle activity seen in the EMG.

Main differences between conditions were found in the movement field (MF) and movement evoked field 1 (MEF1) corresponding to activity in the sensorimotor cortex during the execution of the movement and afferent feedback after movement respectively. The reaction-time task was found to have stronger amplitudes and an additional interesting finding from the reaction-time task was discovered after the stimulus as bilateral insular activation with temporal dispersion.

Two possible main mediators of these results could be the difference in movement execution, seen in the EMG, and the applied electrical stimulus. With current study design it was not possible to differentiate between these possible mediators. In further studies it could be interesting to investigate effects of nociceptive stimulus during movement execution and investigate cortical connectivity between the bilateral insular activation and sensory processing areas.