title: Functional near-infrared spectroscopy maps cortical plasticity underlying altered motor performance induced by transcranial direct current stimulation.
abstract: Transcranial direct current stimulation (tDCS) of the human sensorimotor cortex during physical rehabilitation induces plasticity in the injured brain that improves motor performance. Bi-hemispheric tDCS is a noninvasive technique that modulates cortical activation by delivering weak current through a pair of anodal-cathodal (excitation-suppression) electrodes, placed on the scalp and centered over the primary motor cortex of each hemisphere. To quantify tDCS-induced plasticity during motor performance, sensorimotor cortical activity was mapped during an event-related, wrist flexion task by functional near-infrared spectroscopy (fNIRS) before, during, and after applying both possible bi-hemispheric tDCS montages in eight healthy adults. Additionally, torque applied to a lever device during isometric wrist flexion and surface electromyography measurements of major muscle group activity in both arms were acquired concurrently with fNIRS. This multiparameter approach found that hemispheric suppression contralateral to wrist flexion changed resting-state connectivity from intra-hemispheric to inter-hemispheric and increased flexion speed (p<0.05). Conversely, exciting this hemisphere increased opposing muscle output resulting in a decrease in speed but an increase in accuracy (p<0.05 for both). The findings of this work suggest that tDCS with fNIRS and concurrent multimotor measurements can provide insights into how neuroplasticity changes muscle output, which could find future use in guiding motor rehabilitation.
authors.affiliation: University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Joint Graduate Program in Biomedical Engineering, 500 UTA Boulevard, Arlington, Texas 76010.
authors.forename: Bilal
authors.initials: B
authors.lastname: Khan
authors.forename: Timea
authors.initials: T
authors.lastname: Hodics
authors.forename: Nathan
authors.initials: N
authors.lastname: Hervey
authors.forename: George
authors.initials: G
authors.lastname: Kondraske
authors.forename: Ann M
authors.initials: AM
authors.lastname: Stowe
authors.forename: George
authors.initials: G
authors.lastname: Alexandrakis
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D046690:Deep Brain Stimulation / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000098:blood supply / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013647:Task Performance and Analysis
chemical_list: D006454:Hemoglobins