PMID- 17556392
OWN - NLM
STAT- MEDLINE
DCOM- 20071030
LR  - 20220129
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 583
IP  - Pt 1
DP  - 2007 Aug 15
TI  - Intracortical circuits modulate transcallosal inhibition in humans.
PG  - 99-114
AB  - Previous results using paired-pulse transcranial magnetic stimulation (TMS) have 
      suggested that the excitability of transcallosal (TC) connections between the 
      hand areas of the two motor cortices is modulated by intracortical inhibitory 
      circuits in the same way as corticospinal tract (CTS) projections to spinal 
      motoneurons. Here we describe two further similarities in TC and CTS control 
      using (1) an I-wave facilitation protocol and (2) preconditioning with rTMS. In 
      experiment 1, excitability of TC pathways was measured using interhemispheric 
      inhibition (IHI) and the ipsilateral silent period (iSP), whilst excitability of 
      CTS pathways was measured by recording the EMG response evoked in the first 
      dorsal interosseous muscle contralateral to the conditioning stimulus (cMEP). The 
      intensity of the conditioning stimulus was first adjusted to threshold for 
      evoking IHI and iSP, then pairs of conditioning stimuli were applied randomly at 
      interstimulus intervals (ISIs) from 1.3 to 4.3 ms. IHI and iSP were facilitated 
      at ISI=1.5 ms and 3.0 ms, respectively, as was the MEP evoked by the conditioning 
      stimuli in the contralateral hand. We suggest that TC projections receive 
      I-wave-like facilitation similar to that seen in CTS projections. In experiment 
      2, short interval inhibition of the iSP (SICIiSP), and short interval 
      intracortical inhibition of the cMEP (SICIcMEP) were examined before and after 
      600 pulses of 5 Hz rTMS at 90% resting motor threshold. Both SICIiSP and SICIcMEP 
      were reduced, as was the iSP; the cMEP was unchanged. This shows that the 
      population of inhibitory interneurons that control TC neurons respond in the same 
      way to 5 Hz rTMS as those that control CTS neurons. Taken together, the data from 
      the two experiments suggest that the layer III and layer V pyramidal neurons that 
      give rise to TC and CTS pathways, respectively, are controlled by neuronal 
      circuitry with similar properties.
FAU - Avanzino, L
AU  - Avanzino L
AD  - Sobell Department of Motor Neuroscience and Movement Disorders, Box 66, Institute 
      of Neurology, Queen Square, London WC1N 3BG, UK.
FAU - Teo, J T H
AU  - Teo JT
FAU - Rothwell, J C
AU  - Rothwell JC
LA  - eng
GR  - G0500258/MRC_/Medical Research Council/United Kingdom
PT  - Journal Article
DEP - 20070607
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
SB  - IM
MH  - Adult
MH  - Corpus Callosum/*physiology
MH  - Electromyography
MH  - Evoked Potentials, Motor/physiology
MH  - Female
MH  - Hand/*innervation/physiology
MH  - Humans
MH  - Interneurons/physiology
MH  - Male
MH  - Motor Cortex/anatomy & histology/*physiology
MH  - Motor Neurons/physiology
MH  - Muscle Contraction/physiology
MH  - Neural Pathways/anatomy & histology/*physiology
MH  - Pyramidal Cells/*physiology
MH  - Transcranial Magnetic Stimulation
PMC - PMC2277247
EDAT- 2007/06/09 09:00
MHDA- 2007/10/31 09:00
PMCR- 2008/08/15
CRDT- 2007/06/09 09:00
PHST- 2007/06/09 09:00 [pubmed]
PHST- 2007/10/31 09:00 [medline]
PHST- 2007/06/09 09:00 [entrez]
PHST- 2008/08/15 00:00 [pmc-release]
AID - jphysiol.2007.134510 [pii]
AID - 10.1113/jphysiol.2007.134510 [doi]
PST - ppublish
SO  - J Physiol. 2007 Aug 15;583(Pt 1):99-114. doi: 10.1113/jphysiol.2007.134510. Epub 
      2007 Jun 7.