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Title: Event-related desynchronization during mirror visual feedback : a comparison of older adults and people after stroke
Authors: Fong, KNK 
Ting, KH 
Zhang, JJQ 
Yau, CSF
Issue Date: May-2021
Source: Frontiers in human neuroscience, May 2021, v. 15, 629592
Abstract: Event-related desynchronization (ERD), as a proxy for mirror neuron activity, has been used as a neurophysiological marker for motor execution after mirror visual feedback (MVF). Using EEG, this study investigated ERD upon the immediate effects of single-session MVF in unimanual arm movements compared with the ERD effects occurring without a mirror, in two groups: stroke patients with left hemiplegia and their healthy counterparts. During EEG recordings, each group performed one session of mirror therapy training in three task conditions: with a mirror, with no mirror, and with a covered mirror. An asymmetry index was calculated from the subtraction of the event-related spectrum perturbations between the C3 and C4 electrodes located over the sensorimotor cortices contralateral and ipsilateral to the moved arm. Results of the effect of task versus group in contralateral and ipsilateral motor areas showed that there was a significant effect of task condition at the contralateral motor area in the high beta band (17–35 Hz) at C3. High beta ERD showed that the suppression was greater over the contralateral hemisphere than it was over the ipsilateral hemisphere in both study groups. The magnitude of low beta (12–16 Hz) ERD in patients with stroke was more suppressed in contralesional C3 under the no mirror compared to that of the covered mirror and similarly more suppressed in ipsilesional C4 ERD under the no mirror compared to that of the mirror condition. The correlation analysis revealed that the magnitude of ERSP power correlated significantly with arm severity in the low and high beta bands in patients with stroke, and a higher asymmetry index in the low beta band was associated with higher arm functioning under the no-mirror condition. There was a shift in sensorimotor ERD toward the contralateral hemisphere as induced by MVF accompanying unimanual movement in both stroke patients and healthy controls. The use of ERD in the low beta band as a neurophysiological marker to indicate the relationships between the amount of MVF-induced ERD attenuation and motor severity, and the outcome indicator for improving stroke patients’ neuroplasticity in clinical trials using MVF are warranted to be explored in the future.
Keywords: Event-related desynchronization
Mirror neuron
Mirror visual feedback
Occupational therapy
Publisher: Frontiers Research Foundation
Journal: Frontiers in human neuroscience 
EISSN: 1662-5161
DOI: 10.3389/fnhum.2021.629592
Rights: © 2021 Fong, Ting, Zhang, Yau and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) ( The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
The following publication Fong KNK, Ting KH, Zhang JJQ, Yau CSF and Li LSW (2021) Event-Related Desynchronization During Mirror Visual Feedback: A Comparison of Older Adults and People After Stroke. Front. Hum. Neurosci. 15:629592 is available at
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