title: MEG-based detection and localization of perilesional dysfunction in chronic stroke.
abstract: Post-stroke impairment is associated not only with structural lesions, but also with dysfunction in surviving perilesional tissue. Previous studies using equivalent current dipole source localization of MEG/EEG signals have demonstrated a preponderance of slow-wave activity localized to perilesional areas. Recent studies have also demonstrated the utility of nonlinear analyses such as multiscale entropy (MSE) for quantifying neuronal dysfunction in a wide range of pathologies. The current study utilized beamformer-based reconstruction of signals in source space to compare spectral and nonlinear measures of electrical activity in perilesional and healthy cortices. Data were collected from chronic stroke patients and healthy controls, both young and elderly. We assessed relative power in the delta (1-4 Hz), theta (4-7 Hz), alpha (8-12 Hz) and beta (15-30 Hz) frequency bands, and also measured the nonlinear complexity of electrical activity using MSE. Perilesional tissue exhibited a general slowing of the power spectrum (increased delta/theta, decreased beta) as well as a reduction in MSE. All measures tested were similarly sensitive to changes in the posterior perilesional regions, but anterior perilesional dysfunction was detected better by MSE and beta power. The findings also suggest that MSE is specifically sensitive to electrophysiological dysfunction in perilesional tissue, while spectral measures were additionally affected by an increase in rolandic beta power with advanced age. Furthermore, perilesional electrophysiological abnormalities in the left hemisphere were correlated with the degree of language task-induced activation in the right hemisphere. Finally, we demonstrate that single subject spectral and nonlinear analyses can identify dysfunctional perilesional regions within individual patients that may be ideal targets for interventions with noninvasive brain stimulation.
authors.affiliation: University of Toronto, Department of Psychology, 100 St. George Street, 4th Floor, Sidney Smith Hall, Toronto, ON M5S 3G3, Canada ; Rotman Research Institute, Baycrest Centre, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada.
authors.forename: Ron K O
authors.initials: RK
authors.lastname: Chu
authors.affiliation: Language Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Allen R
authors.initials: AR
authors.lastname: Braun
authors.affiliation: University of Toronto, Department of Psychology, 100 St. George Street, 4th Floor, Sidney Smith Hall, Toronto, ON M5S 3G3, Canada ; University of Toronto, Department of Speech-Language Pathology, 160-500 University Avenue, Toronto, ON M5G 1V7, Canada ; Rotman Research Institute, Baycrest Centre, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada ; Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, 600 Peter Morand Cres., Suite 201, Ottawa, ON K1G 5Z3, Canada.
authors.forename: Jed A
authors.initials: JA
authors.lastname: Meltzer
mesh_terms: D000328:Adult; D000368:Aged; D001037:Aphasia / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D058256:Brain Waves / Q000502:physiology*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000150:complications*; D055815:Young Adult
keywords: Beamformer source reconstruction; Chronic stroke; Magnetoencephalography; Time–frequency analysis