Paired-Pulse TMS and Fine-Wire Recordings Reveal Short-Interval Intracortical Inhibition and Facilitation of Deep Multifidus Muscle Fascicles

Hugo Massé-Alarie; Edith Elgueta Cancino; Cyril Schneider; Paul Hodges

doi:10.1371/journal.pone.0159391

Paired-Pulse TMS and Fine-Wire Recordings Reveal Short-Interval Intracortical Inhibition and Facilitation of Deep Multifidus Muscle Fascicles

PLoS One. 2016 Aug 10;11(8):e0159391. doi: 10.1371/journal.pone.0159391. eCollection 2016.

Authors

Hugo Massé-Alarie¹, Edith Elgueta Cancino², Cyril Schneider¹, Paul Hodges²

Affiliations

¹ Laboratory of Clinical Neuroscience and neuroStimulation, Université Laval (Dept of Rehabilitation), CHU de Québec Research Center, Neuroscience Unit (CHUL), Quebec City, QC, Canada.
² The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury & Health, School of Health & Rehabilitation Sciences, Brisbane, Qld Australia.

Abstract

Objective: Paired-pulse transcranial magnetic stimulation (ppTMS) is used to probe inhibitory and excitatory networks within the primary motor cortex (M1). These mechanisms are identified for limb muscles but it is unclear whether they share properties with trunk muscles. The aim was to determine whether it was possible to test the intracortical inhibition and facilitation of the deep multifidus muscle fascicles (DM) and at which inter-stimulus intervals (ISI).

Methods: In ten pain-free individuals, TMS was applied over M1 and motor evoked potentials (MEP) were recorded using fine-wire electrodes in DM. MEPs were conditioned with subthreshold stimuli at ISIs of 1 to 12 ms to test short-interval intracortical inhibition (SICI) and at 15 ms for long-interval intracortical facilitation. Short-interval facilitation (SICF) was tested using 1-ms ISI.

Results: SICI of DM was consistently obtained with ISI of 1-, 3-, 4- and 12-ms. Facilitation of DM MEP was only identified using SICF paradigm.

Conclusions: A similar pattern of MEP modulation with ISI changes for deep trunk and limb muscles implies that M1 networks share some functional properties.

Significance: The ppTMS paradigm presents a potential to determine how M1 inhibitory and excitatory mechanisms participate in brain re-organization in back pain that affects control of trunk muscles.

MeSH terms

Adult
Electromyography
Evoked Potentials, Motor / physiology
Humans
Muscle Contraction
Paraspinal Muscles / physiology*
Time Factors
Transcranial Magnetic Stimulation / instrumentation
Transcranial Magnetic Stimulation / methods*
Young Adult

Grants and funding

HMA is supported by the Fonds de Recherche du Québec - Santé, Université Laval and the Canadian Institutes for Health Research (studentship & travel grant). PH is supported by a Senior Principal Research Fellowship from the National Health and Medical Research Council of Australia (ID1102905). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.