- Title
- Determination of anodal tDCS intensity threshold for reversal of corticospinal excitability: an investigation for induction of counter-regulatory mechanisms
- Creator
- Hassanzahraee, Maryam; Nitsche, Michael; Zoghi, Maryam; Jaberzadeh, Shapour
- Date
- 2020
- Type
- Text; Journal article
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/193098
- Identifier
- vital:18108
- Identifier
-
https://doi.org/10.1038/s41598-020-72909-4
- Identifier
- ISSN:2045-2322
- Abstract
- Transcranial direct current stimulation is applied to modulate activity, and excitability of the brain. Basically, LTP-like plasticity is induced when anodal tDCS (a-tDCS) is applied over the primary motor cortex. However, it has been shown that specific parameters of a-tDCS can induce a plasticity reversal. We aimed to systematically assess the intensity threshold for reversal of the direction of plasticity induced by a-tDCS, monitored by corticospinal excitability (CSE), and explored mechanisms regulating this reversal. Fifteen healthy participants received a-tDCS in pseudo-random order for 26 min with four intensities of 0.3, 0.7, 1, and 1.5 mA. To measure CSE changes, single-pulse TMS was applied over the left M1, and motor evoked potentials of a contralateral hand muscle were recorded prior to a-tDCS, immediately and 30-min post-intervention. Paired-pulse TMS was used to evaluate intracortical excitation and inhibition. CSE increased significantly following a-tDCS with an intensity of 0.7 mA however, the expected effect decreased and even reversed at intensities of 1 and 1.5 mA. ICF was significantly increased while SICI and LICI decreased at 0.7 mA. On the other hand, a significant decrease of ICF, but SICI and LICI enhancement was observed at intensities of 1, and 1.5 mA. The present findings show an intensity threshold of ≥ 1 mA for 26 min a-tDCS to reverse LTP- into LTD-like plasticity. It is suggested that increasing stimulation intensity, with constant stimulation duration, activates counter-regulatory mechanisms to prevent excessive brain excitation. Therefore, stimulation intensity and plasticity induced by a-tDCS might non-linearly correlate in scenarios with prolonged stimulation duration.
- Publisher
- Nature Publishing Group
- Relation
- Scientific Reports Vol. 10, no. 1 (2020), p. 16108-16108
- Rights
- All metadata describing materials held in, or linked to, the repository is freely available under a CC0 licence
- Rights
- http://creativecommons.org/licenses/by/4.0/
- Rights
- Copyright This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
- Rights
- Open Access
- Subject
- Adult; Cortex (motor); Electrodes; Evoked Potentials, Motor - physiology; Excitability; Female; Humans; Inhibition, Psychological; Long-term potentiation; Male; Motor Cortex - physiology; Motor evoked potentials; Muscle, Skeletal - physiology; Neural Inhibition - physiology; Neural plasticity; Neuronal Plasticity - physiology; Neuroscience; Pyramidal tracts; Pyramidal Tracts - physiology; Synaptic plasticity; Transcranial Direct Current Stimulation - methods; Transcranial Magnetic Stimulation - methods; MD Multidiscplinary
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