tDCS polarity effects in motor and cognitive domains: a meta-analytical review
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In vivo effects of transcranial direct current stimulation (tDCS) have attracted much attention nowadays as this area of research spreads to both the motor and cognitive domains. The common assumption is that the anode electrode causes an enhancement of cortical excitability during stimulation, which then lasts for a few minutes thereafter, while the cathode electrode generates the opposite effect, i.e., anodal-excitation and cathodal-inhibition effects (AeCi). Yet, this dual-polarity effect has not been observed in all tDCS studies. Here, we conducted a meta-analytical review aimed to investigate the homogeneity/heterogeneity of the effect sizes of the AeCi dichotomy in both motor and cognitive functions. The AeCi effect was found to occur quite commonly with motor investigations and rarely in cognitive studies. When the anode electrode is applied over a non-motor area, in most cases, it will cause an excitation as measured by a relevant cognitive or perceptual task; however, the cathode electrode rarely causes an inhibition. We found homogeneity in motor studies and heterogeneity in cognitive studies with the electrode’s polarity serving as a moderator that can explain the source of heterogeneity in cognitive studies. The lack of inhibitory cathodal effects might reflect compensation processes as cognitive functions are typically supported by rich brain networks. Further insights as to the polarity and domain interaction are offered, including subdivision to different classes of cognitive functions according to their likelihood of being affected by stimulation.
KeywordsCognitive Meta-analysis Motor Transcranial direct current stimulation (tDCS)
This study was supported by the Israel Academy of Sciences grant no. 100/10 and an ERC starting grant awarded to ML (Inspire 200512).
- 2Csifcsak G, Antal A, Hillers F, Levold M, Bachmann CG, Happe S, Nitsche MA, Ellrich J, Paulus W (2009) Modulatory effects of transcranial direct current stimulation on laser-evoked potentials. Am Acad Pain Mad 10(1):122–132Google Scholar
- Hern JEC, Landgren S, Phillips CG, Porter R (1962) Selective excitation of corticofugal neurones by surface-anodal stimulation of the baboon’s motor cortex. J Physiol 161:73–90Google Scholar
- 10Kirimoto H, Ogata K, Onishi H, Oyama M, Goto Y, Tobimatsu S (2009) Transcranial direct current stimulation over premotor cortex modifies the excitability of the ipsilateral primary motor and somatosensory cortices. IEEE 978-1-4244-3316-2/09Google Scholar
- 12Lang 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 56:634–639PubMedCrossRefGoogle Scholar
- 39Mameli F, Mrakic-Sposta S, Vergari M, Fumagallia M, Macisa M, Ferrucci R, Nordio Francesco, Consonni D, Sartori G, Priori A (2010) Dorsolateral prefrontal cortex specifically processes general—but not personal—knowledge deception: multiple brain networks for lying. Behav Brain Res 211(2):164–168PubMedCrossRefGoogle Scholar
- Rosenthal R (1991) Meta-analytic procedure for social research. Sage publication, Newbury parkGoogle Scholar
- Shadish WR, Haddock CK (1994) Combining estimate of effect size. In: Cooper HM, Hedges LV (eds) The handbook of research synthesis. Russel Sage foundation, New York, pp 261–281Google Scholar
- 15Siebner 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):3379–3385PubMedCrossRefGoogle Scholar
- 46Sparing R, Thimm M, Hesse MD, Kust J, Karbe H, Fink GR (2009) Bidirectional alterations of interhemispheric parietal balance by non-invasive cortical stimulation. Brain 1–10Google Scholar
- 48Timea VE, Kaya E, Andrea A, Marta Z, Iren H, Paulus W, Gyula K (2007) Cathodal transcranial direct current stimulation over the parietal cortex modifies facial gender adaptation. Ideggyogy 60(11–12):474–479Google Scholar