Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms
Background: Transcranial direct current stimulation (tDCS) is used to induce neuroplasticity in the human brain. Within certain limits of stimulation duration, anodal tDCS (a-tDCS) over the primary motor cortex induces long term potentiation- (LTP) like plasticity. A reversal of the direction of pla...
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| Format: | Article |
| Language: | English |
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Elsevier
2020-05-01
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| Series: | Brain Stimulation |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S1935861X20300498 |
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| author | Maryam Hassanzahraee Michael A. Nitsche Maryam Zoghi Shapour Jaberzadeh |
| author_facet | Maryam Hassanzahraee Michael A. Nitsche Maryam Zoghi Shapour Jaberzadeh |
| author_sort | Maryam Hassanzahraee |
| collection | DOAJ |
| description | Background: Transcranial direct current stimulation (tDCS) is used to induce neuroplasticity in the human brain. Within certain limits of stimulation duration, anodal tDCS (a-tDCS) over the primary motor cortex induces long term potentiation- (LTP) like plasticity. A reversal of the direction of plasticity has however been described with prolonged a-tDCS protocols. Objective: We aimed to systematically investigate the intervention duration threshold for reversal of a-tDCS-induced effects on corticospinal excitability (CSE) and to determine the probable mechanisms involved in these changes. Methods: Fifteen healthy participants received a-tDCS of 1 mA for five different durations in pseudo-random session order. Transcranial magnetic stimulation (TMS) was delivered over the left M1, and motor evoked potentials (MEPs) of a contralateral hand muscle were recorded before, immediately and 30 min following intervention to measure CSE changes. Short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long interval facilitation (LIF) were assessed via paired-pulse TMS protocols. Results: A-tDCS significantly increased CSE as expected at stimulation durations of 22 and 24 min. However, this effect of a-tDCS on CSE decreased and even reversed when stimulation duration increased to 26, 28, and 30 min. Respective alterations of ICF, LIF, and SICI indicate the involvement of glutamatergic, and GABAergic systems in these effects. Conclusions: These results confirm a duration threshold for reversal of the excitability-enhancing effect of a-tDCS with stimulation durations ≥ 26 min. Counter-regulatory mechanisms are discussed as a mechanistic foundation for these effects, which might prevent excessive brain activation. |
| first_indexed | 2024-12-15T00:21:33Z |
| format | Article |
| id | doaj.art-f29d95743e4d4ab0bf4e71ba4d548d14 |
| institution | Directory Open Access Journal |
| issn | 1935-861X |
| language | English |
| last_indexed | 2024-12-15T00:21:33Z |
| publishDate | 2020-05-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Brain Stimulation |
| spelling | doaj.art-f29d95743e4d4ab0bf4e71ba4d548d142022-12-21T22:42:17ZengElsevierBrain Stimulation1935-861X2020-05-01133832839Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanismsMaryam Hassanzahraee0Michael A. Nitsche1Maryam Zoghi2Shapour Jaberzadeh3Non-invasive Brain Stimulation & Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia; Corresponding author.Department of Neurology, University Medical Hospital Bergmannsheil, Bochum, Germany; Dept. Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, GermanyDepartment of Rehabilitation, Nutrition and Sport, School of Allied Health, Discipline of Physiotherapy, La Trobe University, Melbourne, AustraliaNon-invasive Brain Stimulation & Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, AustraliaBackground: Transcranial direct current stimulation (tDCS) is used to induce neuroplasticity in the human brain. Within certain limits of stimulation duration, anodal tDCS (a-tDCS) over the primary motor cortex induces long term potentiation- (LTP) like plasticity. A reversal of the direction of plasticity has however been described with prolonged a-tDCS protocols. Objective: We aimed to systematically investigate the intervention duration threshold for reversal of a-tDCS-induced effects on corticospinal excitability (CSE) and to determine the probable mechanisms involved in these changes. Methods: Fifteen healthy participants received a-tDCS of 1 mA for five different durations in pseudo-random session order. Transcranial magnetic stimulation (TMS) was delivered over the left M1, and motor evoked potentials (MEPs) of a contralateral hand muscle were recorded before, immediately and 30 min following intervention to measure CSE changes. Short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long interval facilitation (LIF) were assessed via paired-pulse TMS protocols. Results: A-tDCS significantly increased CSE as expected at stimulation durations of 22 and 24 min. However, this effect of a-tDCS on CSE decreased and even reversed when stimulation duration increased to 26, 28, and 30 min. Respective alterations of ICF, LIF, and SICI indicate the involvement of glutamatergic, and GABAergic systems in these effects. Conclusions: These results confirm a duration threshold for reversal of the excitability-enhancing effect of a-tDCS with stimulation durations ≥ 26 min. Counter-regulatory mechanisms are discussed as a mechanistic foundation for these effects, which might prevent excessive brain activation.http://www.sciencedirect.com/science/article/pii/S1935861X20300498PlasticityTMSMotor evoked potentialCorticospinal excitabilityMotor cortexTranscranial direct current stimulation |
| spellingShingle | Maryam Hassanzahraee Michael A. Nitsche Maryam Zoghi Shapour Jaberzadeh Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms Brain Stimulation Plasticity TMS Motor evoked potential Corticospinal excitability Motor cortex Transcranial direct current stimulation |
| title | Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms |
| title_full | Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms |
| title_fullStr | Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms |
| title_full_unstemmed | Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms |
| title_short | Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms |
| title_sort | determination of anodal tdcs duration threshold for reversal of corticospinal excitability an investigation for induction of counter regulatory mechanisms |
| topic | Plasticity TMS Motor evoked potential Corticospinal excitability Motor cortex Transcranial direct current stimulation |
| url | http://www.sciencedirect.com/science/article/pii/S1935861X20300498 |
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