Abstract
Weak transcranial direct current stimulation (tDCS) can induce long lasting changes in cortical excitability. In the present study we asked whether tDCS applied to the left primary motor cortex (M1) also produces aftereffects distant from the site of the stimulating electrodes. We therefore tested corticospinal excitability in the left and the right M1 and transcallosal excitability between the two cortices using transcranial magnetic stimulation (TMS) before and after applying tDCS. Eight healthy subjects received 10 min of anodal or cathodal tDCS (1 mA) to the left M1. We examined the amplitude of contralateral motor evoked potentials (MEPs) and the onset latency and duration of transcallosal inhibition with single pulse TMS. MEPs evoked from the tDCS stimulated (left) M1 were increased by 32% after anodal and decreased by 27% after cathodal tDCS, while transcallosal inhibition evoked from the left M1 remained unchanged. The effect on MEPs evoked from the left M1 lasted longer for cathodal than for anodal tDCS. MEPs evoked from the right M1 were unchanged whilst the duration of transcallosal inhibition evoked from the right M1 was shortened after cathodal tDCS and prolonged after anodal tDCS. The duration of transcallosal inhibition returned to control values before the effect on the MEPs from the left M1 had recovered. These findings are compatible with the idea that tDCS-induced aftereffects in the cortical motor system are limited to the stimulated hemisphere, and that tDCS not only affects corticospinal circuits involved in producing MEPs but also inhibitory interneurons mediating transcallosal inhibition from the contralateral hemisphere.
Similar content being viewed by others
References
Bindman LJ, Lippold OCJ, Redfearn JWT (1964) The action of brief polarizing currents on the cerebral cortex of the rat (1) during current flow and (2) in the production of long-lasting after-effects. J Physiol (Lond) 172:369–382
Gerschlager W, Siebner HR, Rothwell JC (2001) Decreased corticospinal excitability after subthreshold 1 Hz rTMS over lateral premotor cortex. Neurology 57:449–455
Gilio F, Rizzo V, Siebner HR, Rothwell JC (2003) Effects on the right motor hand-area excitability produced by low-frequency rTMS over human contralateral homologous cortex. J Physiol 551:563–573
Liebetanz D, Nitsche MA, Tergau F, Paulus W (2002) Pharmacological approach to the mechanisms of transcranial DC-stimulation-induced after-effects of human motor cortex excitability. Brain 125:2238–2247
Macdonell RA, Shapiro BE, Chiappa KH, Helmers SL, Cros D, Day BJ, Shahani BT (1991) Hemispheric threshold differences for motor evoked potentials produced by magnetic coil stimulation. Neurology 41:1441–1444
Meyer BU, Roricht S, Grafin von Einsiedel H, Kruggel F, Weindl A (1995) Inhibitory and excitatory interhemispheric transfers between motor cortical areas in normal humans and patients with abnormalities of the corpus callosum. Brain 118:429–440
Munchau A, Bloem BR, Irlbacher K, Trimble MR, Rothwell JC (2002) Functional connectivity of human premotor and motor cortex explored with repetitive transcranial magnetic stimulation. J Neurosci 22:554–561
Nitsche MA, Paulus W (2000) Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. J Physiol 527:633–639
Nitsche MA, Paulus W (2001) Sustained excitability elevations induced by transcranial DC motor cortex stimulation in humans. Neurology 57:1899–1901
Nitsche M, Nitsche M, Klein C, Tergau F, Rothwell J, Paulus W (2003) Level of action of cathodal DC polarisation induced inhibition of the human motor cortex. Clin Neurophysiol 114:600–604
Oldfield RC (1971) The assessment and analysis of handedness: the Edinburgh inventory. Neuropsychologia 9:97–113
Purpura DP, McMurtry JG (1965) Intracellular activities and evoked potential changes during polarization of motor cortex. J Neurophysiol 28:166–185
Rothwell JC, Hallett M, Berardelli A, Eisen A, Rossini P, Paulus W (1999) Magnetic stimulation: motor evoked potentials. The International Federation of Clinical Neurophysiology. Electroencephalogr Clin Neurophysiol Suppl 52:97–103
Schambra HM, Sawaki L, Cohen LG (2003) Modulation of excitability of human motor cortex (M1) by 1 Hz transcranial magnetic stimulation of the contralateral M1. Clin Neurophysiol 114:130–133
Siebner HR, Lang N, Ward N, Rothwell JC, Paulus W, Lemon RN, Frackowiak RS (2003) Widespread changes in regional neuronal activity after a single session of transcranial direct current stimulation. Hum Brain Mapp 2003, poster #310
Triggs WJ, Calvanio R, Macdonell RA, Cros D, Chiappa KH (1994) Physiological motor asymmetry in human handedness: evidence from transcranial magnetic stimulation. Brain Res 636:270–276
Wassermann EM, Wedegaertner FR, Ziemann U, George MS, Chen R (1998) Crossed reduction of human motor cortex excitability by 1-Hz transcranial magnetic stimulation. Neurosci Lett 250:141–144
Acknowledgements
Nicolas Lang was supported by the Deutsche Forschungsgemeinschaft (DFG) within the European Graduiertenkolleg 632: “Neuroplasticity: from Molecules to Systems”.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Lang, N., Nitsche, M.A., Paulus, W. et al. Effects of transcranial direct current stimulation over the human motor cortex on corticospinal and transcallosal excitability. Exp Brain Res 156, 439–443 (2004). https://doi.org/10.1007/s00221-003-1800-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00221-003-1800-2