Transcranial Magnetic Stimulation Mapping using the Pseudorandom Walk Method to Measure Training-Induced Plasticity

Stroke is a leading cause of long-term disability. Functional recovery involves
both spontaneous recovery and motor learning. The latter relies on the ability
of the primary motor cortex (M1) to functionally reorganize and adapt the
existing muscle synergies. Muscle areas on the M1 can be measured by applying
Transcranial Magnetic Stimulation (TMS) over the motor cortex while
simultaneously measuring the amplitudes of the motor evoked potentials (MEPs)
in the Electromyography (EMG) signal of the target muscle. A recently developed
mapping technique, the pseudorandom walk method, significantly reduces time
needed to perform TMS mapping without sacrificing the reliability of the
measurements. Due to this faster technique, it is now possible to map several
muscles at once, which was not viable before with the traditional mapping
method. To investigate the movement control of the upper-limb we focus on the
proximal Medial Deltoid (MD) and the distal Brachioradialis (BR) muscles. These
muscles have not been mapped yet using the pseudorandom walk method.
Furthermore, motor learning studies mostly remain focused on the effects of
short-term training. Thus, the goal of this experiment is to use the
pseudorandom walk method to map the two muscles of interest and measure their
change after a long-term motor learning task. We will compare the obtained
motor maps, the mean MEPs measured at the hotspot, the overlap in the cortical
representations, and the potential for interhemispheric transfer before and
after the period of the motor learning.

Primary objective: To acquire motor maps of the BR and the MD muscles by using
the pseudorandom walk method and assess their change after long-term motor
learning.
Secondary objectives: Compute muscle synergies from the motor maps and assess
their change. Investigate potential changes on the contralateral motor maps of
the side of the body that will not undergo any motor learning.

Crossover intervention study

Motor learning of a complex upper-limb motor task - throwing of darts

Healthy participants will visit the Erasmus MC on 2 days for a total of 2 hours
per visit. There is a 6-week period in between the two sessions. In this time,
half of the participants will go through a motor learning of a complex motor
task at home. All the materials will be provided. These participants will be
asked to keep a diary of their performance. In this study, the safety measures
are applied as described in recent brain stimulation reviews. There are no
serious risks associated with this study. The minimal risks associated with the
discharge of the TMS coil at higher intensity levels are the loud sounds and a
temporary discomfort in the muscles on the head.