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Neural Plasticity
Volume 2015, Article ID 309546, 8 pages
http://dx.doi.org/10.1155/2015/309546
Research Article

Cortical Excitability Measured with nTMS and MEG during Stroke Recovery

1BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Hospital and University of Helsinki, 00029 Helsinki, Finland
2Neuroscience Center, University of Helsinki, 00014 Helsinki, Finland
3Department of Neurology, Helsinki University Hospital and University of Helsinki, 00029 Helsinki, Finland
4Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, P.O. Box 15100, 00076 Espoo, Finland
5Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, 41345 Gothenburg, Sweden
6Department of Neurology, Sahlgrenska University Hospital, 41345 Gothenburg, Sweden

Received 27 February 2015; Accepted 5 May 2015

Academic Editor: Yong Jeong

Copyright © 2015 Jyrki P. Mäkelä et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective. Stroke alters cortical excitability both in the lesioned and in the nonlesioned hemisphere. Stroke recovery has been studied using transcranial magnetic stimulation (TMS). Spontaneous brain oscillations and somatosensory evoked fields (SEFs) measured by magnetoencephalography (MEG) are modified in stroke patients during recovery. Methods. We recorded SEFs and spontaneous MEG activity and motor threshold (MT) short intracortical inhibition (SICI) and intracortical facilitation (ICF) with navigated TMS (nTMS) at one and three months after first-ever hemispheric ischemic strokes. Changes of MEG and nTMS parameters attributed to gamma-aminobutyrate and glutamate transmission were compared. Results. ICF correlated with the strength and extent of SEF source areas depicted by MEG at three months. The nTMS MT and event-related desynchronization (ERD) of beta-band MEG activity and SICI and the beta-band MEG event-related synchronization (ERS) were correlated, but less strongly. Conclusions. This first report using sequential nTMS and MEG in stroke recovery found intra- and interhemispheric correlations of nTMS and MEG estimates of cortical excitability. ICF and SEF parameters, MT and the ERD of the lesioned hemisphere, and SICI and ERS of the nonlesioned hemisphere were correlated. Covarying excitability in the lesioned and nonlesioned hemispheres emphasizes the importance of the hemispheric balance of the excitability of the sensorimotor system.