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Comparison between adaptive and fixed stimulus paired-pulsetranscranial magnetic stimulation (ppTMS) in normal subjects
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Clinical Neurophysiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Clinical Neurophysiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Clinical Neurophysiology.
2017 (English)In: Clinical Neurophysiology Practice, ISSN 2467-981X, p. 91-97Article in journal (Refereed) Published
Abstract [en]

Objectives

Paired-pulse TMS (ppTMS) examines cortical excitability but may require lengthy test procedures and fine tuning of stimulus parameters due to the inherent variability of the elicited motor evoked potentials (MEPs) and their tendency to exhibit a ‘ceiling/floor effects’ in inhibition trials. Aiming to overcome some of these limitations, we implemented an ‘adaptive’ ppTMS protocol and compared the obtained excitability indices with those from ‘conventional’ fixed-stimulus ppTMS.

Methods

Short- and long interval intracortical inhibition (SICI and LICI) as well as intracortical facilitation (ICF) were examined in 20 healthy subjects by adaptive ppTMS and fixed-stimulus ppTMS. The test stimulus intensity was either adapted to produce 500 μV MEPs (by a maximum likelihood strategy in combination with parameter estimation by sequential testing) or fixed to 120% of resting motor threshold (rMT). The conditioning stimulus was 80% rMT for SICI and ICF and 120% MT for LICI in both tests.

Results

There were significant (p < 0.05) intraindividual correlations between the two methods for all excitability measures. There was a clustering of SICI and LICI indices near maximal inhibition (‘ceiling effect’) in fixed-stimulus ppTMS which was not observed for adaptive SICI and LICI.

Conclusions

Adaptive ppTMS excitability data correlates to those acquired from fixed-stimulus ppTMS.

Significance

Adaptive ppTMS is easy to implement and may serve as a more sensitive method to detect changes in cortical inhibition than fixed stimulus ppTMS. Whether equally confident data are produced by less stimuli with our adaptive approach (as already confirmed for motor threshold estimation) remains to be explored.

Place, publisher, year, edition, pages
2017. p. 91-97
National Category
Neurosciences
Identifiers
URN: urn:nbn:se:uu:diva-342567DOI: 10.1016/j.cnp.2017.04.001OAI: oai:DiVA.org:uu-342567DiVA, id: diva2:1184810
Available from: 2018-02-22 Created: 2018-02-22 Last updated: 2018-03-15Bibliographically approved

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Amandusson, ÅsaFlink, RolandAxelson, Hans

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