Effects of a common transcranial direct current stimulation (tDCS) protocol on motor evoked potentials found to be highly variable within individuals over 9 testing sessions
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Transcranial direct current stimulation (tDCS) uses a weak electric current to modulate neuronal activity. A neurophysiologic outcome measure to demonstrate reliable tDCS modulation at the group level is transcranial magnetic stimulation engendered motor evoked potentials (MEPs). Here, we conduct a study testing the reliability of individual MEP response patterns following a common tDCS protocol. Fourteen participants (7m/7f) each underwent nine randomized sessions of 1 mA, 10 min tDCS (3 anode; 3 cathode; 3 sham) delivered using an M1/orbito-frontal electrode montage (sessions separated by an average of ~5.5 days). Fifteen MEPs were obtained prior to, immediately following and in 5 min intervals for 30 min following tDCS. TMS was delivered at 130 % resting motor threshold using neuronavigation to ensure consistent coil localization. A number of non-experimental variables were collected during each session. At the individual level, considerable variability was seen among different testing sessions. No participant demonstrated an excitatory response ≥20 % to all three anodal sessions, and no participant demonstrated an inhibitory response ≥20 % to all three cathodal sessions. Intra-class correlation revealed poor anodal and cathodal test–retest reliability [anode: ICC(2,1) = 0.062; cathode: ICC(2,1) = 0.055] and moderate sham test–retest reliability [ICC(2,1) = 0.433]. Results also revealed no significant effect of tDCS at the group level. Using this common protocol, we found the effects of tDCS on MEP amplitudes to be highly variable at the individual level. In addition, no significant effects of tDCS on MEP amplitude were found at the group level. Future studies should consider utilizing a more strict experimental protocol to potentially account for intra-individual response variations.
KeywordsTranscranial direct current stimulation (tDCS) Transcranial magnetic stimulation (TMS) Motor evoked potentials (MEPs) Longitudinal Reliability
ARC-SRI: Science of Learning Research Centre (Project Number SR120300015).
- Chang WH, Fried PJ, Saxena S, Jannati A, Gomes-Osman J, Kim YH, Pascual-Leone A (2016) Optimal number of pulses as outcome measure in neuronavigated transcranial magnetic stimulation. Clin Neurophysiol [Epub ahead of print]Google Scholar
- de Tommaso M, Invitto S, Ricci K, Lucchese V, Delussi M, Quattromini P et al (2014) Effects of anodal TDCS stimulation of left parietal cortex on visual spatial attention tasks in men and women across menstrual cycle. Neurosci Lett 574:21–25. doi: 10.1016/j.neulet.2014.05.014 CrossRefPubMedGoogle Scholar
- Di Lazzaro V, Manganelli F, Dileone M, Notturno F, Esposito M, Capasso M et al (2012) The effects of prolonged cathodal direct current stimulation on the excitatory and inhibitory circuits of the ipsilateral and contralateral motor cortex. J Neural Transm 119(12):1499–1506. doi: 10.1007/s00702-012-0845-4 CrossRefPubMedGoogle Scholar
- Fleiss JL (1986) The design and analysis of clinical experiments. Wiley, New YorkGoogle Scholar
- Lang N, Siebner HR, Ernst D, Nitsche MA, Paulus W, Lemon RN, Rothwell JC (2004b) Preconditioning with transcranial direct current stimulation sensitizes the motor cortex to rapid-rate transcranial magnetic stimulation and controls the direction of after-effects. Biol Psychiatry 56(9):634–639CrossRefPubMedGoogle Scholar
- O’Connell NE, Cossar J, Marston L, Wand BM, Bunce D, Moseley GL, De Souza LH (2012) Rethinking clinical trials of transcranial direct current stimulation: participant and assessor blinding is inadequate at intensities of 2mA. PLoS One 7(10):e47514. doi: 10.1371/journal.pone.0047514 CrossRefPubMedPubMedCentralGoogle Scholar
- Power HA, Norton JA, Porter CL, Doyle Z, Hui I, Chan KM (2006) Transcranial direct current stimulation of the primary motor cortex affects cortical drive to human musculature as assessed by intermuscular coherence. J Physiol 577(Pt 3):795–803. doi: 10.1113/jphysiol.2006.116939 CrossRefPubMedPubMedCentralGoogle Scholar
- Roche N, Lackmy A, Achache V, Bussel B, Katz R (2011) Effects of anodal transcranial direct current stimulation over the leg motor area on lumbar spinal network excitability in healthy subjects. J Physiol 589(Pt 11):2813–2826. doi: 10.1113/jphysiol.2011.205161 CrossRefPubMedPubMedCentralGoogle Scholar
- Siebner HR, Lang N, Rizzo V, Nitsche MA, Paulus W, Lemon RN, Rothwell JC (2004) Preconditioning of low-frequency repetitive transcranial magnetic stimulation with transcranial direct current stimulation: evidence for homeostatic plasticity in the human motor cortex. J Neurosci 24(13):3379–3385CrossRefPubMedGoogle Scholar
- Suzuki K, Fujiwara T, Tanaka N, Tsuji T, Masakado Y, Hase K et al (2012) Comparison of the after-effects of transcranial direct current stimulation over the motor cortex in patients with stroke and healthy volunteers. Int J Neurosci 122(11):675–681. doi: 10.3109/00207454.2012.707715 CrossRefPubMedGoogle Scholar
- Wassermann E, Epstein C, Ziemann U (2008) Oxford handbook of transcranial magnetic stimulation. Oxford University Press, OxfordGoogle Scholar