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Intracortical Inhibition Within the Primary Motor Cortex Can Be Modulated by Changing the Focus of Attention
Published on: September 11, 2017
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Physiological Processes Underlying Short Interval Intracortical Facilitation in the Human Motor Cortex.
Mehdi A J Van den Bos1, Parvathi Menon1, James Howells2
1Westmead Clinical School, University of Sydney, Sydney, NSW, Australia.
Frontiers in Neuroscience
|April 27, 2018
Summary
Short interval intracortical facilitation (SICF) is a unique brain stimulation response. This study suggests SICF is mediated by I-wave facilitation, offering new insights into cortical excitability.
Area of Science:
- Neuroscience
- Motor Control
- Cortical Excitability
Background:
- Short interval intracortical facilitation (SICF) is a paired pulse transcranial magnetic stimulation (TMS) response.
- SICF is a unique analog to motor cortex (M1) inhibitory circuits.
- Understanding SICF's physiological basis is crucial for interpreting TMS studies.
Purpose of the Study:
- To investigate the physiological processes underlying SICF development.
- To utilize the reliable threshold tracking TMS technique.
- To explore the cortical contributions to facilitatory circuits.
Main Methods:
- TMS was applied to 35 healthy controls using circular and figure-of-eight coils.
- Threshold tracking TMS technique was employed to monitor motor evoked potentials (MEPs).
- Motor evoked potentials were recorded from the abductor pollicis brevis muscle.
Main Results:
- SICF was consistently observed between 1-5 ms interstimulus intervals (ISIs), with peaks at 1.5 and 3 ms using a circular coil.
- A higher tracking target significantly reduced SICF, while a figure-of-eight coil increased it.
- No correlation was found between SICF and short-interval intracortical inhibition (SICI) or intracortical facilitation (ICF), nor was age a factor.
Conclusions:
- SICF appears to be mediated by I-wave facilitation.
- The findings provide novel insights into the mechanisms of intracortical facilitation.
- This study highlights the reliability of threshold tracking TMS for studying SICF.
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