title: Identifying Dysfunctional Cortex: Dissociable Effects of Stroke and Aging on Resting State Dynamics in MEG and fMRI.
abstract: Spontaneous signals in neuroimaging data may provide information on cortical health in disease and aging, but the relative sensitivity of different approaches is unknown. In the present study, we compared different but complementary indicators of neural dynamics in resting-state MEG and BOLD fMRI, and their relationship with blood flow. Participants included patients with post-stroke aphasia, age-matched controls, and young adults. The complexity of brain activity at rest was quantified in MEG using spectral analysis and multiscale entropy (MSE) measures, whereas BOLD variability was quantified as the standard deviation (SDBOLD), mean squared successive difference (MSSD), and sample entropy of the BOLD time series. We sought to assess the utility of signal variability and complexity measures as markers of age-related changes in healthy adults and perilesional dysfunction in chronic stroke. The results indicate that reduced BOLD variability is a robust finding in aging, whereas MEG measures are more sensitive to the cortical abnormalities associated with stroke. Furthermore, reduced complexity of MEG signals in perilesional tissue were correlated with hypoperfusion as assessed with arterial spin labeling (ASL), while no such relationship was apparent with BOLD variability. These findings suggest that MEG signal complexity offers a sensitive index of neural dysfunction in perilesional tissue in chronic stroke, and that these effects are clearly distinguishable from those associated with healthy aging.
authors.affiliation: Rotman Research Institute, Baycrest Health Sciences Toronto, ON, Canada.
authors.forename: Aneta
authors.initials: A
authors.lastname: Kielar
authors.affiliation: Rotman Research Institute, Baycrest Health Sciences Toronto, ON, Canada.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Deschamps
authors.affiliation: Rotman Research Institute, Baycrest Health SciencesToronto, ON, Canada; Department of Psychology, University of TorontoToronto, ON, Canada.
authors.forename: Ron K O
authors.initials: RK
authors.lastname: Chu
authors.affiliation: Rotman Research Institute, Baycrest Health SciencesToronto, ON, Canada; Department of Speech-Language Pathology, University of TorontoToronto, ON, Canada.
authors.forename: Regina
authors.initials: R
authors.lastname: Jokel
authors.affiliation: Rotman Research Institute, Baycrest Health Sciences Toronto, ON, Canada.
authors.forename: Yasha B
authors.initials: YB
authors.lastname: Khatamian
authors.affiliation: Rotman Research Institute, Baycrest Health SciencesToronto, ON, Canada; Department of Medical Biophysics, University of TorontoToronto, ON, Canada; Canadian Partnership for Stroke RecoveryOttawa, ON, Canada.
authors.forename: Jean J
authors.initials: JJ
authors.lastname: Chen
authors.affiliation: Rotman Research Institute, Baycrest Health SciencesToronto, ON, Canada; Department of Psychology, University of TorontoToronto, ON, Canada; Department of Speech-Language Pathology, University of TorontoToronto, ON, Canada; Canadian Partnership for Stroke RecoveryOttawa, ON, Canada.
authors.forename: Jed A
authors.initials: JA
authors.lastname: Meltzer
keywords: BOLD variability; MEG; aging; aphasia; blood flow; multiscale entropy; stroke