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.
Highlights
Hemiparetic upper limb impairment is a leading cause of longterm physical disability after stroke
One of the possible explanations is that the parietal–frontal area encompasses the so-called human mirror neuron system (MNS), which can be activated during both the observation and execution of movements (Rizzolatti and Craighero, 2004)
The study’s inclusion criteria were patients who had: (1) a neurological condition with unilateral left hemiparesis; (2) a score between levels 2 and 6 on the Functional Test of Hemiplegic Upper Extremity (FTHUE) (Fong et al, 2004), and higher scores represent a higher level of arm functioning; (3) chronic stroke, with the onset of the neurological condition having occurred more than 6 months previously; (4) the ability to understand and follow simple verbal instructions; (5) the ability to participate in a therapy session lasting at least 30 min; (6) the ability to be community ambulant, with or without aids; (7) normal or corrected-to-normal vision; and (8) right dominance before the stroke
Summary
Hemiparetic upper limb impairment is a leading cause of longterm physical disability after stroke. 70% experience permanent upper extremity hemiplegia (Jørgense et al, 2000), and 33–60% will continue to have no function at 6 months post-stroke (Kwakkel and Kollen, 2013). Facilitation of motor relearning in order to elicit positive neuroplasticity of the damaged brain area during the rehabilitation of a hemiparetic arm has always been a challenging task for occupational therapy (Stoykov and Madhavan, 2015). Mirror therapy has been used by occupational therapists as an effective and cost-effective intervention for arm hemiparesis following stroke. Evidence shows that it can benefit stroke patients in their arm recovery at the subacute stage (Toh and Fong, 2012). One of the possible explanations is that the parietal–frontal area encompasses the so-called human mirror neuron system (MNS), which can be activated during both the observation and execution of movements (Rizzolatti and Craighero, 2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
