Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

• Type of Material: Article
• Authors: Jacqueline A. Palmer, Emory University; Lewis Wheaton, Emory University; Whitney A. Gray, Emory University; Mary Alice Saltao da Silva, Emory University; Steven Wolf, Emory University; Michael Borich, Emory University
• Language: English
• Date: 2019-07-22
• Publisher: Sage Publications Inc.
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © The Author(s) 2019.
• Final Published Version (URL): http://dx.doi.org/10.1177/1545968319862552
• Title of Journal or Parent Work: Neurorehabilitation and Neural Repair
• Volume: 33
• Issue: 9
• Start Page: 762
• End Page: 774
• Grant/Funding Information: This research was supported by the American Heart Association [AHA00035638] and the Eunice Kennedy Shriver National Institutes of Child Health & Human Development of the National Institutes of Health [K12HD055931].
• Keywords: Transcallossal inhibition; Stroke patients; Brain stimulation; Recovery; Movement; Neurosciences & Neurology; Clinical Neurology; transcallosal inhibition; Connectivity; Modulation; Science & Technology; Life Sciences & Biomedicine; Silent period; electroencephalography; transcranial magnetic stimulation; Rehabilitation; Activation; Cortex; stroke; GABA; Interhemispheric inhibition
• Research Categories: Health Sciences, Medicine and Surgery; Biology, Neuroscience; Engineering, Biomedical

Abstract

Background/Objective: We investigated interhemispheric interactions in stroke survivors by measuring TMS-evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP). Methods: Participants with (n=19) and without (n=14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre and post-TMS interhemispheric beta coherence (15–30Hz) between motor areas in both conditions and the ipsilateral silent period (iSP) duration during the active condition. Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared to controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within or between-group differences in coherence were observed at rest. Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with post-stroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.