Page 302 - MEGIN Book Of Abstracts - 2023

biomarker candidates of post-stroke motor recovery. Aalto University School of Science, P.O. Box 12200, 00760
Consistent with the view of stroke as a 'circuitopathy', AALTO, Espoo, Finland; Aalto NeuroImaging, Aalto University
functional neuroimaging measures probing functional School of Science, P.O. Box 12200, 00760 AALTO, Espoo, Fin-
connectivity may also prove informative in post-stroke land; Department of Neurology, Helsinki University Hospital
recovery. An important step in the development of and Clinical Neurosciences, Neurology, University of Helsinki,
biomarkers based on functional neural network con- P.O. Box 340, 00029 HUS, Helsinki, Finland. Electronic address:
nectivity is the establishment of causality between con- riikka.aikio@helsinki.fi; BABA Center, Department of Clinical
nectivity and post-stroke recovery. Current evidence Neurophysiology, Children's Hospital, University of Helsinki
predominantly involves statistical correlations between and Helsinki University Hospital, P.O. Box 347, 00029 HUS, Hel-
connectivity measures and post-stroke behavioural sinki, Finland; Department of Computer Science, University of
status, either cross-sectionally or serially over time. Verona, 37134 Verona, Italy; Department of Neuroradiology,
However, the advancement of functional connectivity University of Helsinki and Helsinki University Hospital, P.O. Box
application in stroke depends on devising experiments 340, 00029 HUS, Helsinki, Finland; Department of Neurosci-
that infer causality. In 1965, Sir Austin Bradford Hill ence and Biomedical Engineering, Aalto University School of
introduced nine viewpoints to consider when deter- Science, P.O. Box 12200, 00760 AALTO, Espoo, Finland; Aalto
mining the causality of an association: (i) strength; (ii) NeuroImaging, Aalto University School of Science, P.O. Box
consistency; (iii) specificity; (iv) temporality; (v) bio- 12200, 00760 AALTO, Espoo, Finland; Department of Psychol-
logical gradient; (vi) plausibility; (vii) coherence; (viii) ogy, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä,
experiment; and (ix) analogy. Collectively referred to as Finland
the Bradford Hill Criteria, these points have been widely
adopted in epidemiology. In this review, we assert ABSTRACT In healthy subjects, motor cortex activity
the value of implementing Bradford Hill's framework and electromyographic (EMG) signals from contract-
to stroke rehabilitation and neuroimaging. We focus ing contralateral muscle show coherence in the beta
on the role of neural network connectivity measure- (15-30 Hz) range. Corticomuscular coherence (CMC)
ments acquired from task-oriented and resting-state is considered a sign of functional coupling between
functional MRI, EEG, magnetoencephalography and muscle and brain. Based on prior studies, CMC is
functional near-infrared spectroscopy in describing and altered in stroke, but functional significance of this
predicting post-stroke behavioural status and recovery. finding has remained unclear. Here, we examined CMC
We also identify research opportunities within each in acute stroke patients and correlated the results with
Bradford Hill tenet to shift the experimental paradigm clinical outcome measures and corticospinal tract (CST)
from correlation to causation. integrity estimated with diffusion tensor imaging (DTI).
During isometric contraction of the extensor carpi
Keywords: causality, connectivity, neuroimaging, rehabili- radialis muscle, EMG and magnetoencephalographic
tation, stroke oscillatory signals were recorded from 29 patients
with paresis of the upper extremity due to ischemic
Brain: a journal of neurology (2022), Vol. 145, No. 4 stroke and 22 control subjects. CMC amplitudes and
(34932786) (7 citations) peak frequencies at 13-30 Hz were compared between
the two groups. In the patients, the peak frequency in
both the affected and the unaffected hemisphere was
CMC is more than a measure of corticospinal tract significantly (p < 0.01) lower and the strength of CMC
integrity in acute stroke patients (2021) was significantly (p < 0.05) weaker in the affected hemi-
sphere compared to the control subjects. The strength
Aikio, R; Laaksonen, K; Sairanen, V; Parkkonen, E; Abou of CMC in the patients correlated with the level of tac-
Elseoud, A; Kujala, J; Forss, N tile sensitivity and clinical test results of hand function.
In contrast, no correlation between measures of CST
Department of Neuroscience and Biomedical Engineering, integrity and CMC was found. The results confirm the

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C