Effects of Theta Burst Stimulation on Modulation of Mirror Illusion-induced Rhythm Suppression in Stroke

Overview

The study aims to test the hypothesis that rTMS in the form of theta burst stimulation (TBS) over the ipsilateral and contralateral motor cortices can modulate mirror illusion-induced rhythm suppression while observing unilateral arm movement in stroke individuals. The investigators further hypothesize that this intervention will lead to the revision of interhemispheric asymmetry. Finally, this study will also explore the longitudinal relationship between rhythm suppression and motor recovery as indicated by motor excitability in the form of MEP. The results of this study will provide significant new information regarding neurophysiological motor relearning mechanisms which could inform the development and evaluation of innovative treatments for individuals with stroke

Stroke is the leading cause of physical disability. Facilitating the process of motor relearning would greatly accelerate the rehabilitation of motor functions and elicit positive neuroplasticity of the damaged brain area. Previous research has already explored the feasibility of motor priming techniques embedded in stroke rehabilitation programs using strategies such as non-invasive brain stimulation (NIBS) and mirror therapy (MT). These treatments are usually implemented along with the standardized rehabilitation, sequentially or simultaneously, and have been demonstrated to be more effective than the standardized rehabilitation programs alone. Mirror neuron, as indicated traditionally by the decrease in the amplitude of Mu rhythm, i.e. a suppression over central electrodes of electroencephalography (EEG), reflects the "seeing" of movement after "perception". Such oscillations are based on neural substrates that are discharged during the observation and execution of a motor act, which is also associated with other human functions, such as imitation, language, etc. The core mirror neuron system (MNS) is thought to be located in the premotor and the primary sensorimotor cortices, indicating that motor learning could be enhanced during action observation and overt movement. Preliminary research has shown that repetitive Transcranial Magnetic Stimulation (rTMS) can enhance the corticomotor excitability in mirror neurons during both observation of movement (by others) or imagined movement in healthy subjects; in particular, as measured by enhanced motor evoked potentials (MEP). Increases in MEP has also been induced by short-term action observation and mirror visual feedback in stroke survivors. However, it is not yet known if MNS can be activated by TMS in MT following a stroke, and the relationship between mirror neuron activation and clinical improvements in stroke remains unclear. The investigators have already published preliminary findings in patients with hemiplegic upper extremity, rTMS, and MT. Here, the investigators propose to test the hypothesis that rTMS in the form of theta-burst stimulation (TBS) over the ipsilateral and contralateral motor cortices can modulate mirror illusion-induced rhythm suppression while observing unilateral arm movement in stroke individuals. The investigators further hypothesize that this intervention will lead to the revision of interhemispheric asymmetry. Finally, this study will also explore the longitudinal relationship between rhythm suppression and motor recovery as indicated by motor excitability in the form of MEP. The results of this study will provide significant new information regarding neurophysiological motor relearning mechanisms which could inform the development and evaluation of innovative treatments for individuals with stroke