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Online Transcranial Magnetic Stimulation Protocol for Measuring Cortical Physiology Associated with Response Inhibition
Published on: February 8, 2018
Intracortical circuits modulate transcallosal inhibition in humans
L Avanzino1, J T H Teo, J C Rothwell
1Sobell Department of Motor Neuroscience and Movement Disorders, Box 66, Institute of Neurology, Queen Square, London WC1N 3BG, UK.
The Journal of Physiology
|June 9, 2007
Summary
Transcallosal (TC) and corticospinal tract (CTS) pathways show similar modulation by intracortical inhibitory circuits. Both pathways exhibit I-wave-like facilitation and respond similarly to repetitive transcranial magnetic stimulation (rTMS).
Area of Science:
- Neuroscience
- Motor Control
- Neurophysiology
Background:
- Previous studies suggest transcallosal (TC) connections are modulated similarly to corticospinal tract (CTS) projections by intracortical inhibitory circuits.
- Further investigation is needed to confirm similarities in the control of TC and CTS pathways.
Purpose of the Study:
- To investigate similarities in the modulation of TC and CTS pathways using I-wave facilitation and preconditioning with repetitive transcranial magnetic stimulation (rTMS).
- To compare the effects of inhibitory circuits on TC projections and CTS projections to spinal motoneurons.
Main Methods:
- Experiment 1 utilized paired-pulse transcranial magnetic stimulation (TMS) to measure interhemispheric inhibition (IHI) and ipsilateral silent period (iSP) for TC pathways, and motor evoked potentials (MEPs) for CTS pathways.
- Experiment 2 examined short-interval intracortical inhibition (SICI) of iSP (SICIiSP) and cMEP (SICIcMEP) before and after 5 Hz rTMS preconditioning.
Main Results:
- TC and CTS pathways demonstrated I-wave-like facilitation at specific interstimulus intervals (ISIs).
- Both SICIiSP and SICIcMEP were reduced after 5 Hz rTMS, indicating similar responses of inhibitory interneurons controlling TC and CTS neurons.
- The iSP was reduced, while the cMEP remained unchanged post-rTMS.
Conclusions:
- TC and CTS pathways share similar I-wave-like facilitation properties.
- The inhibitory interneurons modulating TC and CTS pathways exhibit comparable responses to 5 Hz rTMS.
- Neuronal circuitry controlling layer III (TC) and layer V (CTS) pyramidal neurons possesses similar properties.
