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Intracortical Inhibition Within the Primary Motor Cortex Can Be Modulated by Changing the Focus of Attention
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Intracortical Inhibition and Surround Inhibition in the Motor Cortex: A TMS-EEG Study

Giorgio Leodori1, Nivethida Thirugnanasambandam2, Hannah Conn2

  • 1IRCCS NEUROMED, Pozzilli, Italy.

Frontiers in Neuroscience
|June 29, 2019
PubMed
Abstract

Insights

Short-latency intracortical inhibition (SICI) and motor surround inhibition (mSI) share inhibitory mechanisms, modulating cortical excitability. These findings clarify the neurophysiology underlying fine motor control in healthy individuals.

Area of Science:

  • Neuroscience
  • Motor Control
  • Cortical Physiology

Background:

  • Short-latency intracortical inhibition (SICI) and motor surround inhibition (mSI) are TMS-investigated cortical phenomena.
  • mSI is crucial for fine finger movements, with SICI potentially contributing to its genesis.
  • The precise mechanisms of SICI and mSI remain incompletely understood.

Purpose of the Study:

  • To investigate the cortical physiology of SICI and mSI using TMS-evoked potentials (TEPs).
  • To explore the relationship between SICI, mSI, and motor execution in healthy subjects.

Main Methods:

  • Single-pulse (sp) and paired-pulse (pp) TMS applied to the ADM muscle hotspot.
  • EEG and EMG recorded during rest and at the onset of index finger movement.
  • SICI and mSI quantified from motor evoked potentials (MEPs); TEPs analyzed across regions of interest.

Main Results:

  • Widespread reduction of the N100 inhibitory component observed at movement onset, indicating cortical facilitation.
  • At the motor cortex level, SICI and mSI exhibited similar TEP modulation: reduced P30 and increased N45 amplitudes.
  • Distinct TEP patterns were associated with the presence or absence of mSI.

Conclusions:

  • SICI and mSI appear to modulate cortical excitability through common inhibitory pathways.
  • Findings provide insights into the neurophysiological underpinnings of motor control.
  • Shared mechanisms suggest a coordinated role for SICI and mSI in motor function.
Keywords:
SICITMS-EEGelectroencephalographyinhibitionmotor cortextranscranial magnetic stimulation

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