PMID- 9438711
OWN - NLM
STAT- MEDLINE
DCOM- 19980225
LR  - 20191211
IS  - 0014-4819 (Print)
IS  - 0014-4819 (Linking)
VI  - 117
IP  - 3
DP  - 1997 Dec
TI  - Intracortical inhibition of lower limb motor-evoked potentials after paired 
      transcranial magnetic stimulation.
PG  - 437-43
AB  - The aim of the present study was to determine the characteristics of 
      intracortical inhibition in the motor cortex areas representing lower limb 
      muscles using paired transcranial magnetic (TMS) and transcranial electrical 
      stimulation (TES) in healthy subjects. In the first paradigm (n=8), paired 
      magnetic stimuli were delivered through a double cone coil and motor evoked 
      potentials (MEPs) were recorded from quadriceps (Q) and tibialis anterior (TA) 
      muscles during relaxation. The conditioning stimulus strength was 5% of the 
      maximum stimulator output below the threshold MEP evoked during weak voluntary 
      contraction of TA (33+/-5%). The test stimulus (67+/-2%) was 10% of the 
      stimulator output above the MEP threshold in the relaxed TA. Interstimulus 
      intervals (ISIs) from 1-15 ms were examined. Conditioned TA MEPs were 
      significantly suppressed (P<0.01) at ISIs of less than 5 ms (relative amplitude 
      from 20-50% of the control). TA MEPs tended to be only slightly facilitated at 
      9-ms and 10-ms ISIs. The degree of MEP suppression was not different between 
      right and left TA muscles despite the significant difference in size of the 
      control responses (P<0.001). Also, conditioned MEPs were not significantly 
      different between Q and TA. The time course of TA MEP suppression, using 
      electrical test stimuli, was similar to that found using TMS. In the second 
      paradigm (n=2), the suppression of TA MEPs at 2, 3, and 4 ms ISIs was examined at 
      three conditioning intensities with the test stimulation kept constant. For the 
      pooled 2- to 4-ms ISI data, relative amplitudes were 34+/-6%, 61+/-5%, and 
      98+/-9% for conditioning intensities of 0.95, 0.90, and 0.85x active threshold, 
      respectively (P<0.01). In conclusion, the suppression of lower limb MEPs 
      following paired TMS showed similar characteristics to the intracortical 
      inhibition previously described for the hand motor area.
FAU - Stokic, D S
AU  - Stokic DS
AD  - Division of Restorative Neurology and Human Neurobiology, Baylor College of 
      Medicine, Houston, Texas, USA. dstokic@mmrcrehab.org
FAU - McKay, W B
AU  - McKay WB
FAU - Scott, L
AU  - Scott L
FAU - Sherwood, A M
AU  - Sherwood AM
FAU - Dimitrijevic, M R
AU  - Dimitrijevic MR
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Germany
TA  - Exp Brain Res
JT  - Experimental brain research
JID - 0043312
SB  - IM
MH  - Adult
MH  - Conditioning, Psychological/physiology
MH  - Electric Stimulation
MH  - Electromagnetic Fields
MH  - Evoked Potentials, Motor/*physiology
MH  - Humans
MH  - Leg/*physiology
MH  - Male
MH  - Middle Aged
MH  - Motor Cortex/*physiology
MH  - Muscle, Skeletal/*physiology
MH  - Neural Inhibition
MH  - Physical Stimulation
EDAT- 1998/01/23 00:00
MHDA- 1998/01/23 00:01
CRDT- 1998/01/23 00:00
PHST- 1998/01/23 00:00 [pubmed]
PHST- 1998/01/23 00:01 [medline]
PHST- 1998/01/23 00:00 [entrez]
AID - 10.1007/s002210050238 [doi]
PST - ppublish
SO  - Exp Brain Res. 1997 Dec;117(3):437-43. doi: 10.1007/s002210050238.