Timing of motor cortical stimulation during planar robotic training differentially impacts neuroplasticity in older adults

Crystal L Massie; Shailesh S Kantak; Priya Narayanan; George F Wittenberg

doi:10.1016/j.clinph.2014.06.053

Timing of motor cortical stimulation during planar robotic training differentially impacts neuroplasticity in older adults

Clin Neurophysiol. 2015 May;126(5):1024-32. doi: 10.1016/j.clinph.2014.06.053. Epub 2014 Sep 16.

Authors

Crystal L Massie¹, Shailesh S Kantak², Priya Narayanan³, George F Wittenberg⁴

Affiliations

¹ Physical Therapy and Rehabilitation Sciences Department, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
² Moss Rehabilitation Research Institute, Elkins Park, PA 19027, USA; Physical Therapy and Rehabilitation Sciences Department, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
³ Department of Neurology, University of Maryland School of Medicine, and Maryland Exercise and Robotics Center of Excellence, Veterans Affairs Medical Center, Baltimore, MD 21201, USA.
⁴ Geriatrics Research, Education & Clinical Center, Veterans Affairs Medical Center, Baltimore, MD 21201, USA; Department of Neurology, University of Maryland School of Medicine, and Maryland Exercise and Robotics Center of Excellence, Veterans Affairs Medical Center, Baltimore, MD 21201, USA; Physical Therapy and Rehabilitation Sciences Department, University of Maryland School of Medicine, Baltimore, MD 21201, USA. Electronic address: gwittenb@grecc.umaryland.edu.

Abstract

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.

Keywords: Aging; Motor control; Neuroplasticity; Reaching; Rehabilitation; Transcranial magnetic stimulation.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Age Factors
Aged
Evoked Potentials, Motor*
Female
Humans
Male
Motor Cortex / physiology*
Motor Skills*
Movement
Muscle, Skeletal / physiology
Neuronal Plasticity*
Reaction Time / physiology
Robotics
Transcranial Magnetic Stimulation

Abstract

Publication types

MeSH terms

Grants and funding