title: Evaluating interhemispheric cortical responses to transcranial magnetic stimulation in chronic stroke: A TMS-EEG investigation.
abstract: TMS-evoked cortical responses can be measured using simultaneous electroencephalography (TMS-EEG) to directly quantify cortical connectivity in the human brain. The purpose of this study was to evaluate interhemispheric cortical connectivity between the primary motor cortices (M1s) in participants with chronic stroke and controls using TMS-EEG. Ten participants with chronic stroke and four controls were tested. TMS-evoked responses were recorded at rest and during a typical TMS assessment of transcallosal inhibition (TCI). EEG recordings from peri-central gyral electrodes (C3 and C4) were evaluated using imaginary phase coherence (IPC) analyses to quantify levels of effective interhemispheric connectivity. Significantly increased TMS-evoked beta (15-30Hz frequency range) IPC was observed in the stroke group during ipsilesional M1 stimulation compared to controls during TCI assessment but not at rest. TMS-evoked beta IPC values were associated with TMS measures of transcallosal inhibition across groups. These results suggest TMS-evoked EEG responses can index abnormal effective interhemispheric connectivity in chronic stroke.
authors.affiliation: Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University School of Medicine, 1441 Clifton Rd NE, R228, Atlanta, GA 30322 USA. Electronic address: michael.borich@emory.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Borich
authors.affiliation: School of Applied Physiology, Georgia Institute of Technology, 555 14th St., Room 1309E, Atlanta, GA 30332, USA.
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Wheaton
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada.
authors.forename: Sonia M
authors.initials: SM
authors.lastname: Brodie
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada.
authors.forename: Bimal
authors.initials: B
authors.lastname: Lakhani
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada; Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada.
authors.forename: Lara A
authors.initials: LA
authors.lastname: Boyd
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D002908:Chronic Disease; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D020521:Stroke / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation
keywords: Beta; Coherence; Connectivity; EEG; GABA; Motor cortex; Rehabilitation; Stroke; TMS; TMS-EEG