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Updated: Apr 23, 2026

Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation
Published on: February 23, 2020
Associative plasticity in surround inhibition circuits in human motor cortex
Daniele Belvisi1, Panagiotis Kassavetis, Matteo Bologna
1Neuromed Institute IRCCS, Via Atinense 18, 86077, Pozzilli, IS, Italy.
Motor surround inhibition (mSI), crucial for neural signal contrast, was modulated by paired associative stimulation (PAS). This study demonstrates that mSI is adaptable, influenced by preceding neural activity and experiences.
Area of Science:
- Neuroscience
- Motor Control
- Neuroplasticity
Background:
- Surround inhibition enhances neural signal contrast in the central nervous system.
- Motor surround inhibition (mSI) is a key mechanism in the human motor system, measurable via transcranial magnetic stimulation (TMS).
Purpose of the Study:
- To investigate the modifiability of mSI using a paradigm designed to induce plastic changes in the primary motor cortex (M1).
- To determine if paired associative stimulation (PAS) can alter mSI.
Main Methods:
- Assessed mSI by delivering TMS pulses over the abductor digiti minimi (ADM) during abductor pollicis brevis (APB) activation.
- Applied real PAS (PAS21.5) and sham PAS (PAS100) targeting the M1 area of the APB.
- Measured motor evoked potentials (MEPs) from the ADM before and after PAS interventions.
Main Results:
- Baseline mSI from APB to ADM was confirmed.
- PAS21.5 significantly increased the magnitude of mSI compared to baseline.
- PAS100 did not produce a significant effect on mSI.
Conclusions:
- Motor surround inhibition is an adaptable neural mechanism.
- Prior neural activity and experiences, induced by PAS, can modulate mSI, highlighting its plastic nature.
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