PMID- 27481287
OWN - NLM
STAT- MEDLINE
DCOM- 20170830
LR  - 20181113
IS  - 1432-1106 (Electronic)
IS  - 0014-4819 (Linking)
VI  - 234
IP  - 12
DP  - 2016 Dec
TI  - Motoneuron responsiveness to corticospinal tract stimulation during the silent 
      period induced by transcranial magnetic stimulation.
PG  - 3457-3463
AB  - Based on H-reflex data, spinal mechanisms are proposed to be responsible for the 
      first 50-80 ms of the transcranial magnetic stimulation (TMS)-induced silent 
      period. As several methodological issues can compromise H-reflex validity as a 
      measure of motoneuron excitability, this study used transmastoid stimulation to 
      elicit cervicomedullary motor evoked potentials (CMEPs) during the silent period. 
      Eleven subjects made 1-3 visits which involved 32 or 44 brief (~3 s) isometric 
      elbow flexor contractions at 25 % of maximal torque. During each contraction, 
      transmastoid stimulation was delivered in isolation to elicit an unconditioned 
      CMEP and at interstimulus intervals (ISIs) ranging from 50 to 150 ms after TMS to 
      elicit a conditioned CMEP. Stimulus intensities for TMS and transmastoid 
      stimulation were set to elicit a silent period of ~200 ms and an unconditioned 
      CMEP of 15, 50, or 85 % of the maximal compound muscle action potential (M 
      (max)), respectively. At all ISIs and intensities of transmastoid stimulation, 
      the conditioned CMEP was significantly smaller than the unconditioned CMEP 
      (p < 0.001). However, suppression of the conditioned CMEP was significantly less 
      at 85 % compared to 15 or 50 % M (max) (p = 0.001). Contrary to published 
      H-reflex data, the conditioned CMEP did not recover within 50-80 ms, remaining 
      significantly suppressed at the longest ISI tested (150 ms). These data suggest 
      the spinal portion of the TMS-evoked silent period is considerably longer than 
      reported previously. Transmastoid stimulation, unlike peripheral nerve 
      stimulation, does not impact proprioceptive inflow to motoneurons. Hence, 
      relative to the H-reflex, the CMEP will be subjected to greater afferent-mediated 
      disfacilitation and inhibition due to the TMS-induced muscle twitch.
FAU - Yacyshyn, Alexandra F
AU  - Yacyshyn AF
AD  - Centre for Heart, Lung and Vascular Health, School of Health and Exercise 
      Sciences, The University of British Columbia - Okanagan Campus, 133-1147 Research 
      Road, Kelowna, BC, V1V 1V7, Canada.
FAU - Woo, Emma J
AU  - Woo EJ
AD  - Centre for Heart, Lung and Vascular Health, School of Health and Exercise 
      Sciences, The University of British Columbia - Okanagan Campus, 133-1147 Research 
      Road, Kelowna, BC, V1V 1V7, Canada.
FAU - Price, Maggie C
AU  - Price MC
AD  - Centre for Heart, Lung and Vascular Health, School of Health and Exercise 
      Sciences, The University of British Columbia - Okanagan Campus, 133-1147 Research 
      Road, Kelowna, BC, V1V 1V7, Canada.
FAU - McNeil, Chris J
AU  - McNeil CJ
AD  - Centre for Heart, Lung and Vascular Health, School of Health and Exercise 
      Sciences, The University of British Columbia - Okanagan Campus, 133-1147 Research 
      Road, Kelowna, BC, V1V 1V7, Canada. chris.mcneil@ubc.ca.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20160801
PL  - Germany
TA  - Exp Brain Res
JT  - Experimental brain research
JID - 0043312
SB  - IM
MH  - Adult
MH  - Analysis of Variance
MH  - Electromyography
MH  - Evoked Potentials, Motor/*physiology
MH  - Female
MH  - H-Reflex/physiology
MH  - Humans
MH  - Male
MH  - Motor Cortex/*cytology/physiology
MH  - Motor Neurons/*physiology
MH  - Pyramidal Tracts/*physiology
MH  - Time Factors
MH  - *Transcranial Magnetic Stimulation
MH  - Young Adult
OTO - NOTNLM
OT  - Cervicomedullary motor evoked potential (CMEP)
OT  - Interstimulus interval
OT  - Spinal motoneuron excitability
OT  - Transmastoid stimulation
EDAT- 2016/08/03 06:00
MHDA- 2017/08/31 06:00
CRDT- 2016/08/03 06:00
PHST- 2016/05/06 00:00 [received]
PHST- 2016/07/22 00:00 [accepted]
PHST- 2016/08/03 06:00 [pubmed]
PHST- 2017/08/31 06:00 [medline]
PHST- 2016/08/03 06:00 [entrez]
AID - 10.1007/s00221-016-4742-1 [pii]
AID - 10.1007/s00221-016-4742-1 [doi]
PST - ppublish
SO  - Exp Brain Res. 2016 Dec;234(12):3457-3463. doi: 10.1007/s00221-016-4742-1. Epub 
      2016 Aug 1.