Sebastian H Doeltgen1, Michael C Ridding. 1. Robinson Institute, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, Australia. sebastian.doeltgen@adelaide.edu.au
Abstract
OBJECTIVE: Continuous theta burst stimulation (cTBS) administered at a low stimulus intensity can reduce the excitability of short interval intracortical inhibitory (SICI) networks without affecting the facilitatory intracortical motor networks involved in motor evoked potential (MEP) generation. We sought to determine whether low-intensity, facilitatory, short duration cTBS (300 stimuli over 20 s; cTBS(300)) could modulate SICI without influencing cortical circuits involved in MEP generation. METHODS: MEPs and SICI were assessed at baseline and 5 min and 20 min following cTBS(300) applied at intensities of 60%, 65% or 70% of resting motor threshold (RMT). In addition, the effect of cTBS(300) applied at 60% RMT on low level SICI (20% test MEP suppression) was examined. RESULTS: Low-intensity cTBS(300) facilitated MEP amplitude when applied at 70% RMT, and inhibited MEP amplitude when applied at 65% RMT. In contrast, none of the cTBS(300) protocols had significant effects on moderate or low levels of SICI. CONCLUSIONS: The effects of cTBS(300) on MEP generating motor networks are highly sensitive to stimulation intensity. Low-intensity cTBS(300) does not have isolated, facilitatory effects on SICI networks. SIGNIFICANCE: These results further highlight the difficulties of selectively facilitating the inhibitory circuits within M1 that are responsible for SICI with currently available rTMS paradigms.
OBJECTIVE: Continuous theta burst stimulation (cTBS) administered at a low stimulus intensity can reduce the excitability of short interval intracortical inhibitory (SICI) networks without affecting the facilitatory intracortical motor networks involved in motor evoked potential (MEP) generation. We sought to determine whether low-intensity, facilitatory, short duration cTBS (300 stimuli over 20 s; cTBS(300)) could modulate SICI without influencing cortical circuits involved in MEP generation. METHODS: MEPs and SICI were assessed at baseline and 5 min and 20 min following cTBS(300) applied at intensities of 60%, 65% or 70% of resting motor threshold (RMT). In addition, the effect of cTBS(300) applied at 60% RMT on low level SICI (20% test MEP suppression) was examined. RESULTS: Low-intensity cTBS(300) facilitated MEP amplitude when applied at 70% RMT, and inhibited MEP amplitude when applied at 65% RMT. In contrast, none of the cTBS(300) protocols had significant effects on moderate or low levels of SICI. CONCLUSIONS: The effects of cTBS(300) on MEP generating motor networks are highly sensitive to stimulation intensity. Low-intensity cTBS(300) does not have isolated, facilitatory effects on SICI networks. SIGNIFICANCE: These results further highlight the difficulties of selectively facilitating the inhibitory circuits within M1 that are responsible for SICI with currently available rTMS paradigms.
Authors: Sung Wook Chung; Nigel C Rogasch; Kate E Hoy; Caley M Sullivan; Robin F H Cash; Paul B Fitzgerald Journal: Hum Brain Mapp Date: 2017-11-09 Impact factor: 5.038
Authors: Hamed Ekhtiari; Hosna Tavakoli; Giovanni Addolorato; Chris Baeken; Antonello Bonci; Salvatore Campanella; Luis Castelo-Branco; Gaëlle Challet-Bouju; Vincent P Clark; Eric Claus; Pinhas N Dannon; Alessandra Del Felice; Tess den Uyl; Marco Diana; Massimo di Giannantonio; John R Fedota; Paul Fitzgerald; Luigi Gallimberti; Marie Grall-Bronnec; Sarah C Herremans; Martin J Herrmann; Asif Jamil; Eman Khedr; Christos Kouimtsidis; Karolina Kozak; Evgeny Krupitsky; Claus Lamm; William V Lechner; Graziella Madeo; Nastaran Malmir; Giovanni Martinotti; William M McDonald; Chiara Montemitro; Ester M Nakamura-Palacios; Mohammad Nasehi; Xavier Noël; Masoud Nosratabadi; Martin Paulus; Mauro Pettorruso; Basant Pradhan; Samir K Praharaj; Haley Rafferty; Gregory Sahlem; Betty Jo Salmeron; Anne Sauvaget; Renée S Schluter; Carmen Sergiou; Alireza Shahbabaie; Christine Sheffer; Primavera A Spagnolo; Vaughn R Steele; Ti-Fei Yuan; Josanne D M van Dongen; Vincent Van Waes; Ganesan Venkatasubramanian; Antonio Verdejo-García; Ilse Verveer; Justine W Welsh; Michael J Wesley; Katie Witkiewitz; Fatemeh Yavari; Mohammad-Reza Zarrindast; Laurie Zawertailo; Xiaochu Zhang; Yoon-Hee Cha; Tony P George; Flavio Frohlich; Anna E Goudriaan; Shirley Fecteau; Stacey B Daughters; Elliot A Stein; Felipe Fregni; Michael A Nitsche; Abraham Zangen; Marom Bikson; Colleen A Hanlon Journal: Neurosci Biobehav Rev Date: 2019-07-02 Impact factor: 8.989