T125. Neural oscillatory changes by the co-ordinated multifocal transcranial magnetic burst stimulation in the motor cortex

Abstract

Abnormal neural oscillation in human brains such as overt synchronous beta oscillation in Parkinson’s disease can be one of the neural pathological signatures. How to desynchronize the abnormal oscillation is an important issue for treating the Parkinson’s disease. Therefore, neurologists tried to adopt multiple external oscillatory stimulation to desynchronize the neuronal oscillation of the target frequency as clinical treatment. The concept has been approved by coordinated reset neuromodulation in the deep brain stimulation setting. However, it’s unclear if similar effect can be made through noninvasive stimulation. The noninvasive Co-Ordinated Multifocal Burst Stimulation (COMBS) method by utilizing multiple transcranial magnetic stimulation is proposed in this study for investigating the neural oscillatory changes in the motor cortex. Five healthy volunteer subjects including four females were recruited. Three independent figure of eight coils surrounded the motor hot-spot of extensor indicis proprius (EIP) muscle in the left primary motor cortex. We conducted 50 Hz bursts composed of three pulses with 80% active motor threshold intensity of EIP. To desynchronize the target frequency around 6 Hz, we set one stimulation cycle as every coil firing once randomly, with total duration last for 172.5 ms. Three cycles composed one stimulation block. Total 65 blocks with 315 ms pause between each block were conducted. We implemented finger rapid alternative movement task, which was consisted of three behavioral states including preparation, movement, and resting state. Each subject performed 40 trials before and after COMBS session. EEG signal were collected through 64 EEG channels Neuroscan amplifier system. EEG signal processing contained (1) power spectrum density analysis on the C3 or FC3 channel corresponding to the motor cortex, (2) comparison of the event-related synchronization (ERS) or desynchronization (ERD) before and after the COMBS protocol. The experiment results showed the increasing frequency power from 5 to 20 Hz in the C3 and FC3 electrodes after the COMBS. However, the target frequency around 6 Hz was not desynchronized after stimulation. Consistent ERD and ERS of both α and β frequency during the task were observed. Whereas after COMBS, both α and β frequency spectrum power increased in all behavioral states, without changing desynchronization or synchronization ratio. This study proposed an innovative Co-Ordinated Multifocal Burst Stimulation (COMBS). Experimental findings revealed that the neural oscillation change in the target frequency cannot be decreased effectively by COMBS on healthy motor cortex, but it can increase the power spectrum in the 5–20 Hz frequency composition. In the future work, we will adopt this paradigm on the Parkinson’s disease patients for understanding the further neural oscillation changes on the motor cortex.