Parallel inhibition of cortico-muscular synchronization and cortico-spinal excitability by theta burst TMS in humans.
OBJECTIVE
To investigate the after-effects of theta burst TMS (TBS) on cortico-muscular synchronization, and on cortico-spinal excitability, in humans.


METHODS
We studied 10 healthy subjects using a continuous paradigm of TBS (cTBS), i.e. 600 pulses in 40s. Before and after the cTBS, coherence function was computed as a measure of cortico-muscular synchronization by recording electroencephalogram (EEG) from 19 scalp sites and electromyogram (EMG) from right first dorsal interosseous (FDI) muscle during the isometric contraction. In a separate experiment, motor-evoked potentials (MEPs) in response to single TMS pulses were recorded from the FDI muscle before and after the cTBS, to measure cortico-spinal excitability.


RESULTS
When the cTBS was applied over the left primary motor cortex (M1), the beta-band cortico-muscular coherence for the C3 scalp site, as well as the MEP amplitude significantly decreased in 30-60 min, and then recovered to the original levels in 90-120 min. Neither sham stimulation nor cTBS applied over 2 cm posterior to M1 produced significant effects.


CONCLUSIONS
cTBS-over-M1 can inhibit the cortico-muscular synchronization in parallel with the decline of cortico-spinal excitability.


CONCLUSIONS
Our results provide the first evidence that TBS can efficiently alter the functional cortico-muscular coupling in humans.
Department of Human and Environmental Informatics, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan.
Murat
M
Sağlam
Kaoru
K
Matsunaga
Nobuki
N
Murayama
Yuki
Y
Hayashida
Ying-Zu
YZ
Huang
Ryoji
R
Nakanishi
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D003344:Cortical Synchronization; D004558:Electric Stimulation; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D013826:Theta Rhythm; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult