Page 301 - MEGIN Book Of Abstracts - 2023

Partnership for Stroke Recovery, Ottawa, ON, Canada; frontal, temporal and parietal areas in alpha, and dorsal
Department of Speech-Language Pathology, University of frontal and parietal areas in beta. The node strengths
Toronto, Toronto, ON, Canada; Department of Psychology, from alpha and beta group differences remained sig-
University of Toronto, Toronto, ON, Canada nificant after controlling for nodal spectral power. AEC
correlations with WAB subscales of object naming and
ABSTRACT Post-stroke aphasia is a consequence fluency were significant. Greater alpha connectivity was
of localized stroke-related damage as well as global associated with better naming performance (p = 0.045),
disturbances in a highly interactive and bilaterally- and greater connectivity in both the alpha (p = 0.033)
distributed language network. Aphasia is increas- and beta (p = 0.007) bands was associated with better
ingly accepted as a network disorder and it should be speech fluency performance. The spatial topology was
treated as such when examining the reorganization distinct between these frequency bands. The node
and recovery mechanisms after stroke. In the current strengths remained significant after controlling for age,
study, we sought to investigate reorganized patterns of time post stroke onset, nodal spectral power and nodal
electrophysiological connectivity, derived from resting- lesion sizes. Our findings provide important insights
state magnetoencephalography (rsMEG), in post- into the electrophysiological connectivity profiles (fre-
stroke chronic (>6 months after onset) aphasia. We quency and spatial topology) potentially underpinning
implemented amplitude envelope correlations (AEC), preserved language abilities in stroke survivors with
a metric of connectivity commonly used to describe aphasia.
slower aspects of interregional communication in
resting-state electrophysiological data. The main focus Keywords: Amplitude envelope correlations, Aphasia,
was on identifying the oscillatory frequency bands and Functional connectivity, Magnetoencephalography
frequency-specific spatial topology of connections as- (MEG), Resting-state, Stroke
sociated with preserved language abilities after stroke.
RsMEG was recorded for 5 min in 21 chronic stroke NeuroImage. Clinical (2022), Vol. 34 (35561556) (1 citation)
survivors with aphasia and in 20 matched healthy
controls. Source-level MEG activity was reconstructed
and summarized within 72 atlas-defined brain regions Functional connectivity drives stroke recovery:
(or nodes). A 72 × 72 leakage-corrected connectivity (of shifting the paradigm from correlation to causation
AEC) matrix was obtained for frequencies from theta (2022)
to low-gamma (4-50 Hz). Connectivity was compared
between groups, and, the correlations between Cassidy, Jessica M; Mark, Jasper I; Cramer, Steven C
connectivity and subscale scores from the Western
Aphasia Battery (WAB) were evaluated in the stroke Department of Allied Health Sciences, Division of Physical
group, using partial least squares analyses. Posthoc Therapy, University of North Carolina at Chapel Hill, Chapel
multiple regression analyses were also conducted on a Hill, NC, USA; Department of Neurology, University of Califor-
graph theory measure of node strengths, derived from nia, Los Angeles; and California Rehabilitation Institute, Los
significant connectivity results, to control for node- Angeles, CA, USA
wise properties (local spectral power and lesion sizes)
and demographic and stroke-related variables. Con- ABSTRACT Stroke is a leading cause of disability, with
nectivity among the left hemisphere regions, i.e. those deficits encompassing multiple functional domains.
ipsilateral to the stroke lesion, was greatly reduced in The heterogeneity underlying stroke poses significant
stroke survivors with aphasia compared to matched challenges in the prediction of post-stroke recovery,
healthy controls in the alpha (8-13 Hz; p = 0.011) and prompting the development of neuroimaging-based
beta (15-30 Hz; p = 0.001) bands. The spatial topology biomarkers. Structural neuroimaging measurements,
of hypoconnectivity in the alpha vs. beta bands was particularly those reflecting corticospinal tract injury,
distinct, revealing a greater involvement of ventral are well-documented in the literature as potential

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C