EP 28. Inhibitory online rTMS effects as revealed by cortical silent periods in facial muscles suggest polysynaptic inhibition of speech network. Issue 9 (September 2016)

• Record Type: Journal Article
• Authors: Weiss Lucas, C.; Kallioniemi, E.; Neuschmelting, V.; Nettekoven, C.; Karhu, J.; Goldbrunner, R.; Grefkes, C.; Julkunen, P.
• Is Part Of: Clinical neurophysiology. Volume 127:Issue 9(2016:Sep.)
• Page Start: e245
• Publication Date: 2016-09
• Subjects: Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2016.05.083
• Languages: English
• ISSNs: 1388-2457

Abstract

Abstract : Objective: Inhibitory effects of (online) repetitive transcranial magnetic stimulation (rTMS) are strongly influenced by the stimulation paradigm. In general, cortical inhibition –at least of the primary motor cortex– is reflected by cortical silent periods (cSP) evoked in the respective muscles. This study compares different rTMS protocols regarding their inhibitory effect on the facial motor system during an active language task. Methods: Topographic TMS-mapping of the primary-motor representation (M1) and determination of the resting motor threshold preceded rTMS over hand/face M1 area. during a motor task (thumb abduction/tongue twisting). Here, different stimulation frequencies were applied in a randomized sequence (10 Hz, 30 Hz, 50 Hz).In addition, a paired-pulse TMS protocol (7 ms inter-stimulus-interval) was tested once per subject. The lowest rTMS-intensity leading to clear movement disruption during a motor task (thumb abduction/tongue twisting). was assessed and titled "Motor Inhibition Threshold" (MIT). Thereafter, speech-related areas incl. M1 were stimulated during a picture naming task in three sessions at MIT intensity ( N = 13 healthy subjects). cSPs were analyzed from EMG recordings of different face muscles supplied from both the facial and trigeminal nerve. Results: 30 and 50 Hz rTMS reliably evoked tongue movement disruption ( ICC = 0.65) at lower rTMS-intensities compared to 10 Hz rTMS or paired-pulse TMS. cSPs appeared in all muscles and TMS-conditions. Both muscle and TMS-condition influenced the cSP duration and latency. Conclusions: Higher-frequency rTMS (30/50 Hz) and paired-pulse-TMS evoke comparable inhibitory effects at lower stimulation levels compared to 10 Hz rTMS during a language task. The spatial distribution of cranial muscle cSPs suggests online rTMS effects to affect not only M1 but also distant parts of the language network, supposedly as a result of polysynaptic remote network effects.