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Updated: Jan 21, 2026
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Assessing Primary Motor Cortex Excitability and Excitability Modulation by Pairing Transcranial Magnetic Stimulation with Electromyography
Published on: October 7, 2025
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Somatosensory cortical excitability changes precede those in motor cortex during human motor learning
Hiroki Ohashi1,2, Paul L Gribble1,3,4,5, David J Ostry1,2
1Haskins Laboratories, New Haven, Connecticut.
Journal of Neurophysiology
|August 8, 2019
Summary
Early motor learning involves changes in the somatosensory cortex before the motor cortex. These somatosensory changes during skill acquisition predict learning success, highlighting their crucial role in the initial stages of motor learning.
Area of Science:
- Neuroscience
- Motor Control
- Neuroplasticity
Background:
- Motor learning involves plasticity in both motor and somatosensory cortices.
- Animal studies show cross-cortical potentiation, suggesting interaction between these areas during learning.
- The relative timing and contribution of each cortical area to human motor learning remain unclear.
Purpose of the Study:
- To investigate the time course of changes in primary somatosensory cortex (S1) and primary motor cortex (M1) excitability during human motor skill learning.
- To determine whether plasticity in S1 or M1 occurs first and if these changes correlate with learning outcomes.
Main Methods:
- Participants performed a force production task with trial-to-trial variations.
- Somatosensory evoked potentials (SEPs) via median nerve stimulation measured S1 excitability.
- Motor evoked potentials (MEPs) via TMS measured M1 excitability.
- SEP and MEP measures were interleaved with learning blocks.
Main Results:
- The earliest observed cortical changes during motor learning occurred in somatosensory evoked potentials (SEPs).
- These SEP changes preceded any alterations in motor evoked potentials (MEPs).
- SEP changes correlated with behavioral learning measures, while MEP changes did not.
Conclusions:
- Plasticity in the somatosensory cortex is an early event in human motor learning, occurring before changes in the motor cortex.
- Somatosensory cortical excitability changes during the initial stages of motor skill acquisition are predictive of learning success.
- These findings suggest a critical role for somatosensory plasticity in the early phases of motor learning.
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