TY - JOUR
T1 - No trace of phase
T2 - Corticomotor excitability is not tuned by phase of pericentral mu-rhythm
AU - Madsen, Kristoffer Hougaard
AU - Karabanov, Anke Ninija
AU - Krohne, Lærke Gebser
AU - Safeldt, Mads Gylling
AU - Tomasevic, Leo
AU - Siebner, Hartwig Roman
N1 - Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.
PY - 2019/9/1
Y1 - 2019/9/1
N2 - BACKGROUND: The motor potentials evoked by transcranial magnetic stimulation (TMS) over the motor hand area (M1-HAND) show substantial inter-trial variability. Pericentral mu-rhythm oscillations, might contribute to inter-trial variability. Recent studies targeting mu-activity based on real-time electroencephalography (EEG) reported an influence of mu-power and mu-phase on the amplitude of motor evoked potentials (MEPs) in a preselected group with strong pericentral mu-activity. Other studies that determined mu-power or mu-phase based on post-hoc trial sorting according in non-preselected individuals were largely negative.OBJECTIVES: To reassess if cortico-spinal activity is modulated by the mu-rhythm, we applied single-pulse TMS to the M1-HAND conditional on the phase of the intrinsically expressed pericentral mu-rhythm in 14 non-preselected healthy young participants.METHODS: TMS was given at 0, 90, 180, and 270° of the mu-phase. Based on the absence of effects of mu-phase or mu-power when analyzing the mean MEP amplitudes, we also computed a linear mixed effects model, which included mu-phase, mu-power, inter-stimulus interval (ISIs) as fixed effects, treating the subject factor as a random effect.RESULTS: Mixed model analysis revealed a significant effect of mu-power and ISI, but no effect of mu-phase and no interactions. MEP amplitude scaled linearly with lower mu-power or longer ISIs, but these modulatory effects were very small relative to inter-trial MEP variability.CONCLUSION: Our largely negative results are in agreement with previous offline TMS-EEG studies and point to a possible influence of ISI. Future research needs to clarify under which circumstances the responsiveness of human the M1-HAND to TMS depends on the synchronicity with mu-power and mu-phase.
AB - BACKGROUND: The motor potentials evoked by transcranial magnetic stimulation (TMS) over the motor hand area (M1-HAND) show substantial inter-trial variability. Pericentral mu-rhythm oscillations, might contribute to inter-trial variability. Recent studies targeting mu-activity based on real-time electroencephalography (EEG) reported an influence of mu-power and mu-phase on the amplitude of motor evoked potentials (MEPs) in a preselected group with strong pericentral mu-activity. Other studies that determined mu-power or mu-phase based on post-hoc trial sorting according in non-preselected individuals were largely negative.OBJECTIVES: To reassess if cortico-spinal activity is modulated by the mu-rhythm, we applied single-pulse TMS to the M1-HAND conditional on the phase of the intrinsically expressed pericentral mu-rhythm in 14 non-preselected healthy young participants.METHODS: TMS was given at 0, 90, 180, and 270° of the mu-phase. Based on the absence of effects of mu-phase or mu-power when analyzing the mean MEP amplitudes, we also computed a linear mixed effects model, which included mu-phase, mu-power, inter-stimulus interval (ISIs) as fixed effects, treating the subject factor as a random effect.RESULTS: Mixed model analysis revealed a significant effect of mu-power and ISI, but no effect of mu-phase and no interactions. MEP amplitude scaled linearly with lower mu-power or longer ISIs, but these modulatory effects were very small relative to inter-trial MEP variability.CONCLUSION: Our largely negative results are in agreement with previous offline TMS-EEG studies and point to a possible influence of ISI. Future research needs to clarify under which circumstances the responsiveness of human the M1-HAND to TMS depends on the synchronicity with mu-power and mu-phase.
KW - EEG-Triggered phase targeting
KW - Electroencephalography
KW - Mu rhythm
KW - Pericentral oscillation
KW - Temporal and spatial neuronavigation
KW - Transcranial magnetic stimulation
UR - http://www.scopus.com/inward/record.url?scp=85066075278&partnerID=8YFLogxK
U2 - 10.1016/j.brs.2019.05.005
DO - 10.1016/j.brs.2019.05.005
M3 - Journal article
C2 - 31133479
SN - 1935-861X
VL - 12
SP - 1261
EP - 1270
JO - Brain Stimulation
JF - Brain Stimulation
IS - 5
ER -