Changes in Neuronal Activity after Low Frequency Repetitive Transcranial Magnetic Stimulation

J Korean Neurol Assoc > Volume 23(5); 2005 > Article

Journal of the Korean Neurological Association 2005;23(5): 627-634.

저주파 반복적 경두개자기자극술 후 신경활성도의 변화

김희진, 이민아 조현지 박기덕 최경규 이향운

이화여자대학교 의과대학 신경과학교실

Changes in Neuronal Activity after Low Frequency Repetitive Transcranial Magnetic Stimulation

Hee-Jin Kim

Department of Neurology, College of Medicine, Ewha Womans University and Ewha Medical Research Institute, Seoul, Korea

Abstract

Backgrounds: A one Hz repetitive transcranial magnetic stimulation (rTMS) on the motor cortex is known to decrease motor cortical excitability locally, but the effects on distant areas or at different time points remain unclear. We investigated the spatiotemporal changes in cortical neuronal activity induced by local suprathreshold 1 Hz rTMS.
Methods: Fourteen healthy subjects underwent daily rTMS for 5 consecutive days (1 Hz, 110% of resting motor threshold, 1800 stimuli) over the right temporal cortex (T4 of 10-20 international EEG system). EEG signals were collected at 19 electrodes baseline, before and after each rTMS session, and 2 weeks after the last rTMS session. Band powers of 2-4, 4-8, 8-13, 13-20, 20-40 Hz were calculated. Cross correlation (CC), mutual information (MI), and correlation dimension (D2), the maximum Lyapunov exponent (Lmax) were tested to investigate changes of EEG dynamics of synchronization and complexity. Wilcoxin signed ranks test was used for statistical analysis.
Results: One Hz rTMS immediately caused a significant increase in alpha, gamma, theta band powers and the Lmax (p<0.0001 to 0.041, p<0.0001 to 0.038, respectively) in ipsilateral and contralateral hemispheres after daily rTMS. CC and MI decreased after daily rTMS sessions at the right frontocentrotemporal and left frontotemporal areas (p<0.001 to 0.041).
Conclusions: These findings suggest that focal 1 Hz rTMS can induce a short-term increase in the neuronal complexity and de-synchronization of local neuronal networks at stimulated and distant cortical areas. These findings raise a possibility of therapeutic applications of low frequency rTMS in patients with an abnormally excitable brain cortex such as epilepsy or movement disorders. KeyWords:Repetitive transcranial magnetic stimulation, Nonlinear EEG analysis, Neuronal complexity, De-synchronization, Neuronal network