Related Experiment Video
Updated: Apr 23, 2026
Non-Invasive Modulation and Robotic Mapping of Motor Cortex in the Developing Brain
Published on: July 1, 2019
Timing of motor cortical stimulation during planar robotic training differentially impacts neuroplasticity in older
Crystal L Massie1, Shailesh S Kantak2, Priya Narayanan3
1Physical Therapy and Rehabilitation Sciences Department, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Objective:
The objective was to determine how stimulation timing applied during reaching influenced neuroplasticity related to practice. Older adult participants were studied to increase relevance for stroke rehabilitation and aging.
Methods:
Sixteen participants completed 3 sessions of a reaching intervention with 480 planar robotic movement trials. Sub-threshold, single-pulse transcranial magnetic stimulations (TMS) were delivered during the late reaction time (LRT) period, when muscle activity exceeded a threshold (EMG-triggered), or randomly. Assessments included motor evoked potentials (MEP), amplitude, and direction of supra-threshold TMS-evoked movements and were calculated as change scores from baseline.
Results:
The direction of TMS-evoked movements significantly changed after reaching practice (p<0.05), but was not significantly different between conditions. Movement amplitude changes were significantly different between conditions (p<0.05), with significant increases following the LRT and random conditions. MEP for elbow extensors and flexors, and the shoulder muscle that opposed the practice movement were significantly different between conditions with positive changes following LRT, negative changes following EMG-triggered, and no changes following the random condition. Motor performance including movement time and peak velocity significantly improved following the training but did not differ between conditions.
Conclusions:
The responsiveness of the motor cortex to stimulation was affected positively by stimulation during the late motor response period and negatively during the early movement period, when stimulation was combined with robotic reach practice.
Significance:
The sensitivity of the activated motor cortex to additional stimulation is highly dynamic.
