title: Transspinal direct current stimulation immediately modifies motor cortex sensorimotor maps.
abstract: Motor cortex (MCX) motor representation reorganization occurs after injury, learning, and different long-term stimulation paradigms. The neuromodulatory approach of transspinal direct current stimulation (tsDCS) has been used to promote evoked cortical motor responses. In the present study, we used cathodal tsDCS (c-tsDCS) of the rat cervical cord to determine if spinal cord activation can modify the MCX forelimb motor map. We used a finite-element method model based on coregistered high-resolution rat MRI and microcomputed tomography imaging data to predict spinal current density to target stimulation to the caudal cervical enlargement. We examined the effects of cathodal and anodal tsDCS on the H-reflex and c-tsDCS on responses evoked by intracortical microstimulation (ICMS). To determine if cervical c-tsDCS also modified MCX somatic sensory processing, we examined sensory evoked potentials (SEPs) produced by wrist electrical stimulation and induced changes in ongoing activity. Cervical c-tsDCS enhanced the H-reflex, and anodal depressed the H-reflex. Using cathodal stimulation to examine cortical effects, we found that cervical c-tsDCS immediately modified the forelimb MCX motor map, with decreased thresholds and an expanded area. c-tsDCS also increased SEP amplitude in the MCX. The magnitude of changes produced by c-tsDCS were greater on the motor than sensory response. Cervical c-tsDCS more strongly enhanced forelimb than hindlimb motor representation and had no effect on vibrissal representation. The finite-element model indicated current density localized to caudal cervical segments, informing forelimb motor selectivity. Our results suggest that c-tsDCS augments spinal excitability in a spatially selective manner and may improve voluntary motor function through MCX representational plasticity.
authors: Department of Physiology, Pharmacology and Neuroscience, City College of the City University of New York, New York, New York;
authors: Weiguo
authors: W
authors: Song
authors: Department of Biomedical Engineering, City College of the City University of New York, New York, New York; and.
authors: Dennis Q
authors: DQ
authors: Truong
authors: Department of Biomedical Engineering, City College of the City University of New York, New York, New York; and.
authors: Marom
authors: M
authors: Bikson
authors: Department of Physiology, Pharmacology and Neuroscience, City College of the City University of New York, New York, New York; Graduate Center of the City University of New York, New York, New York jmartin@ccny.cuny.edu.
authors: John H
authors: JH
authors: Martin
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D062187:Spinal Cord Stimulation / Q000379:methods*
keywords: motor cortex; movement control; neuromodulation; rehabilitation; spinal cord