-
- Ryoki Sasaki, John G Semmler, and George M Opie.
- Discipline of Physiology, School of Biomedicine, The University of Adelaide, Adelaide, Australia.
- Neuromodulation. 2022 Jun 1; 25 (4): 614-623.
ObjectivesShort-interval intracortical inhibition (SICI) is a paired-pulse transcranial magnetic stimulation (TMS) technique that is commonly used to quantify intracortical inhibitory tone in the primary motor cortex. Whereas conventional measures of SICI (C-SICI) quantify inhibition by the amplitude of the motor evoked potential (MEP), alternative measures involving threshold tracked SICI (TT-SICI) instead record the TMS intensity required to maintain a consistent MEP amplitude. Although both C-SICI and TT-SICI are thought to reflect inhibition mediated by γ-aminobutyric acid type A (GABAA) receptors, recent evidence suggests that the mechanisms involved with each measure may not be equivalent. This study aimed to use combined TMS-electroencephalography (TMS-EEG) to investigate the cortical mechanisms contributing to C-SICI and TT-SICI.Materials And MethodsIn 20 young adults (30.6 ± 8.1 years), C-SICI and TT-SICI were recorded with multiple conditioning intensities, using both posterior-to-anterior (PA) and anterior-to-posterior (AP) induced currents, and this was compared with the TMS-evoked EEG potential (TEP).ResultsWe found no relationship between the magnitude of C-SICI and TT-SICI within each current direction. However, there was a positive relationship between the slope (derived from multiple conditioning intensities) of inhibition recorded with C-SICI and TT-SICI, but only with a PA current. Furthermore, irrespective of conditioning intensity or current direction, measures of C-SICI were unrelated to TEP amplitude. In contrast, TT-SICI was predicted by the P30 generated with AP stimulation.ConclusionsOur findings further demonstrate that C-SICI and TT-SICI likely reflect different facets of GABAA-mediated processes, with inhibition produced by TT-SICI appearing to align more closely with TMS-EEG measures of cortical excitability.Copyright © 2021 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.
Notes
Knowledge, pearl, summary or comment to share?You can also include formatting, links, images and footnotes in your notes
- Simple formatting can be added to notes, such as
*italics*
,_underline_
or**bold**
. - Superscript can be denoted by
<sup>text</sup>
and subscript<sub>text</sub>
. - Numbered or bulleted lists can be created using either numbered lines
1. 2. 3.
, hyphens-
or asterisks*
. - Links can be included with:
[my link to pubmed](http://pubmed.com)
- Images can be included with:

- For footnotes use
[^1](This is a footnote.)
inline. - Or use an inline reference
[^1]
to refer to a longer footnote elseweher in the document[^1]: This is a long footnote.
.