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Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation.
Brain Stimul 2016 Nov - Dec; 9(6):819-825BS

Abstract

BACKGROUND

Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation technique that has been shown to influence cortical excitability. While polarity specific effects have often been reported, this is not always the case, and variability in both the magnitude and direction of the effects have been observed.

OBJECTIVE/HYPOTHESIS

We aimed to explore the consistency and reliability of the effects of tDCS by investigating changes in cortical excitability across multiple testing sessions in the same individuals. A within subjects design was used to investigate the effects of anodal and cathodal tDCS applied to the motor cortex. Four experimental sessions were tested for each polarity in addition to two sham sessions.

METHODS

Transcranial magnetic stimulation (TMS) was used to measure cortical excitability (TMS recruitment curves). Changes in excitability were measured by comparing baseline measures and those taken immediately following 20 minutes of 2 mA stimulation or sham stimulation.

RESULTS

Anodal tDCS significantly increased cortical excitability at a group level, whereas cathodal tDCS failed to have any significant effects. The sham condition also failed to show any significant changes. Analysis of intra-subject responses to anodal stimulation across four sessions suggest that the amount of change in excitability across sessions was only weakly associated, and was found to have poor reliability across sessions (ICC = 0.276). The effects of cathodal stimulation show even poorer reliability across sessions (ICC = 0.137). In contrast ICC analysis for the two sessions of sham stimulation reflect a moderate level of reliability (ICC = .424).

CONCLUSIONS

Our findings indicate that although 2 mA anodal tDCS is effective at increasing cortical excitability at group level, the effects are unreliable across repeated testing sessions within individual participants. Our results suggest that 2 mA cathodal tDCS does not significantly alter cortical excitability immediately following stimulation and that there is poor reliability of the effect within the same individual across different testing sessions.

Authors+Show Affiliations

School of Psychology, University of Nottingham, Nottingham NG7 2RD, UK.School of Psychology, University of Nottingham, Nottingham NG7 2RD, UK.School of Medicine, Division of Psychiatry, Institute of Mental Health, University of Nottingham, Nottingham NG7 2TU, UK.School of Psychology, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: Stephen.jackson@nottingham.ac.uk.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27387569

Citation

Dyke, Katherine, et al. "Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation." Brain Stimulation, vol. 9, no. 6, 2016, pp. 819-825.
Dyke K, Kim S, Jackson GM, et al. Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation. Brain Stimul. 2016;9(6):819-825.
Dyke, K., Kim, S., Jackson, G. M., & Jackson, S. R. (2016). Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation. Brain Stimulation, 9(6), pp. 819-825. doi:10.1016/j.brs.2016.06.052.
Dyke K, et al. Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation. Brain Stimul. 2016;9(6):819-825. PubMed PMID: 27387569.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation. AU - Dyke,Katherine, AU - Kim,Soyoung, AU - Jackson,Georgina M, AU - Jackson,Stephen R, Y1 - 2016/06/21/ PY - 2015/11/11/received PY - 2016/06/16/revised PY - 2016/06/18/accepted PY - 2016/7/9/pubmed PY - 2017/10/5/medline PY - 2016/7/9/entrez KW - Cortical excitability KW - Motor cortex KW - Transcranial direct current stimulation (tDCS) KW - Transcranial magnetic stimulation (TMS) SP - 819 EP - 825 JF - Brain stimulation JO - Brain Stimul VL - 9 IS - 6 N2 - BACKGROUND: Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation technique that has been shown to influence cortical excitability. While polarity specific effects have often been reported, this is not always the case, and variability in both the magnitude and direction of the effects have been observed. OBJECTIVE/HYPOTHESIS: We aimed to explore the consistency and reliability of the effects of tDCS by investigating changes in cortical excitability across multiple testing sessions in the same individuals. A within subjects design was used to investigate the effects of anodal and cathodal tDCS applied to the motor cortex. Four experimental sessions were tested for each polarity in addition to two sham sessions. METHODS: Transcranial magnetic stimulation (TMS) was used to measure cortical excitability (TMS recruitment curves). Changes in excitability were measured by comparing baseline measures and those taken immediately following 20 minutes of 2 mA stimulation or sham stimulation. RESULTS: Anodal tDCS significantly increased cortical excitability at a group level, whereas cathodal tDCS failed to have any significant effects. The sham condition also failed to show any significant changes. Analysis of intra-subject responses to anodal stimulation across four sessions suggest that the amount of change in excitability across sessions was only weakly associated, and was found to have poor reliability across sessions (ICC = 0.276). The effects of cathodal stimulation show even poorer reliability across sessions (ICC = 0.137). In contrast ICC analysis for the two sessions of sham stimulation reflect a moderate level of reliability (ICC = .424). CONCLUSIONS: Our findings indicate that although 2 mA anodal tDCS is effective at increasing cortical excitability at group level, the effects are unreliable across repeated testing sessions within individual participants. Our results suggest that 2 mA cathodal tDCS does not significantly alter cortical excitability immediately following stimulation and that there is poor reliability of the effect within the same individual across different testing sessions. SN - 1876-4754 UR - https://www.unboundmedicine.com/medline/citation/27387569/Intra_Subject_Consistency_and_Reliability_of_Response_Following_2_mA_Transcranial_Direct_Current_Stimulation_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1935-861X(16)30189-9 DB - PRIME DP - Unbound Medicine ER -