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Changes of inhibitory interneurons during transcallosal stimulations
J Liepert1, M Tegenthoff, J P Malin
1Department of Neurology, Ruhr University Bochum, BG-Kliniken Bergmannsheil Bochum, Federal Republic of Germany.
Journal of Neural Transmission (Vienna, Austria : 1996)
|January 1, 1996
Summary
Ipsilateral transcranial magnetic stimulation (TMS) can shorten the silent period evoked by contralateral cortical stimulation, suggesting TMS activates inhibitory neurons. This highlights distinct neural circuits for motor excitation and inhibition.
Area of Science:
- Neuroscience
- Motor Control
- Cortical Excitability
Background:
- The silent period (SP) is a measure of cortical inhibition.
- Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique.
- Understanding the modulation of SP by ipsilateral TMS is crucial for interpreting cortical excitability.
Purpose of the Study:
- To investigate the effect of ipsilateral TMS on the SP evoked by contralateral cortical stimulation.
- To explore the role of ipsilateral TMS in modulating inhibitory cortical interneurons.
- To differentiate the neuronal circuits underlying motor excitation and inhibition.
Main Methods:
- Ipsilateral TMS was applied before contralateral magnetic or electrical cortical stimulation within 0-50 ms.
- The duration of the silent period was measured.
- Motor evoked potential amplitudes were recorded.
Main Results:
- A decrease in the silent period duration was observed with interstimulus intervals of 20-30 ms using magnetic ipsilateral and contralateral stimuli.
- No significant change in the silent period occurred with ipsilateral magnetic and contralateral electrical stimulations.
- Decreases in motor evoked potential amplitudes were inconsistent.
Conclusions:
- Ipsilateral TMS likely activates inhibitory cortical interneurons, potentially through transcallosal pathways.
- The differential effects of TMS on SP suggest distinct neuronal circuits for motor excitation and inhibition.
- This study provides insights into the complex modulation of cortical excitability by TMS.