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Updated: Jun 2, 2026

Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation
Published on: February 23, 2020
Short-term and long-term plasticity interaction in human primary motor cortex.
Ennio Iezzi1, Antonio Suppa, Antonella Conte
1Neuromed Institute, Sapienza University of Rome, Viale dell'Università, 30 00185 Rome, Italy.
Repetitive transcranial magnetic stimulation (rTMS) can induce short-term plasticity that blocks long-term plasticity in the human motor cortex. This finding suggests metaplasticity mechanisms may underlie these interactions, impacting brain stimulation protocols.
Area of Science:
- Neuroscience
- Neurophysiology
- Brain Stimulation
Background:
- Repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) induces changes in motor evoked potential (MEP) size, reflecting synaptic plasticity.
- These plasticity forms resemble short-term potentiation (STP) and long-term potentiation/depression (LTP/LTD) observed in animal models.
Purpose of the Study:
- To investigate if STP induced by 5-Hz rTMS interferes with LTP/LTD-like plasticity induced by intermittent and continuous theta-burst stimulation (iTBS and cTBS).
- To explore interactions between short-term and long-term rTMS-induced plasticity in the human M1.
Main Methods:
- Healthy human participants received 5-Hz rTMS, iTBS, and cTBS alone and in sequence.
- MEP size changes indexed plasticity; intracortical excitability was tested using paired-pulse TMS.
- Experimental conditions varied rTMS intensity, timing, and train number.
Main Results:
- 5-Hz rTMS alone induced short-lasting MEP changes, while iTBS/cTBS induced long-lasting changes.
- Priming M1 with 10 suprathreshold 5-Hz rTMS trains abolished iTBS/cTBS-induced after-effects.
- 5-Hz rTMS did not alter intracortical excitability.
Conclusions:
- STP elicited by suprathreshold 5-Hz rTMS may abolish iTBS/cTBS-induced LTP/LTD-like plasticity.
- Non-homeostatic metaplasticity mechanisms are suggested to mediate these interactions.
- This study offers novel insights into the interplay of short- and long-term plasticity in human M1.
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