Adaptive threshold hunting for the effects of transcranial direct current stimulation on primary motor cortex inhibition
- 48 Downloads
Primary motor cortex excitability can be modulated by anodal and cathodal transcranial direct current stimulation (tDCS). These neuromodulatory effects may, in part, be dependent on modulation within gamma-aminobutyric acid (GABA)-mediated inhibitory networks. GABAergic function can be quantified non-invasively using adaptive threshold hunting paired-pulse transcranial magnetic stimulation (TMS). The previous studies have used TMS with posterior–anterior (PA) induced current to assess tDCS effects on inhibition. However, TMS with anterior–posterior (AP) induced current in the brain provides a more robust measure of GABA-mediated inhibition. The aim of the present study was to assess the modulation of corticomotor excitability and inhibition after anodal and cathodal tDCS using TMS with PA- and AP-induced current. In 16 young adults (26 ± 1 years), we investigated the response to anodal, cathodal, and sham tDCS in a repeated-measures double-blinded crossover design. Adaptive threshold hunting paired-pulse TMS with PA- and AP-induced current was used to examine separate interneuronal populations within M1 and their influence on corticomotor excitability and short- and long-interval inhibition (SICI and LICI) for up to 60 min after tDCS. Unexpectedly, cathodal tDCS increased corticomotor excitability assessed with AP (P = 0.047) but not PA stimulation (P = 0.74). SICIAP was reduced after anodal tDCS compared with sham (P = 0.040). Pearson’s correlations indicated that SICIAP and LICIAP modulation was associated with corticomotor excitability after anodal (P = 0.027) and cathodal tDCS (P = 0.042). The after-effects of tDCS on corticomotor excitability may depend on the direction of the TMS-induced current used to make assessments, and on modulation within GABA-mediated inhibitory circuits.
KeywordsTranscranial magnetic stimulation Transcranial direct current stimulation Adaptive threshold hunting Intracortical inhibition Current direction
We thank April Ren for the assistance with data collection.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
- Awiszus F, Borckardt JJ (2011) TMS motor threshold assessment tool (MTAT 2.0). http://www.clinicalresearcher.org/software.htm
- Batsikadze G, Moliadze V, Paulus W, Kuo MF, Nitsche MA (2013) Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans. J Physiol Lond 591:1987–2000. https://doi.org/10.1113/jphysiol.2012.249730 CrossRefPubMedPubMedCentralGoogle Scholar
- Heise KF, Niehoff M, Feldheim JF, Liuzzi G, Gerloff C, Hummel FC (2014) Differential behavioral and physiological effects of anodal transcranial direct current stimulation in healthy adults of younger and older age. Front Aging Neurosci 6:146. https://doi.org/10.3389/fnagi.2014.00146 CrossRefPubMedPubMedCentralGoogle Scholar
- Kidgell DJ, Goodwill AM, Frazer AK, Daly RM (2013) Induction of cortical plasticity and improved motor performance following unilateral and bilateral transcranial direct current stimulation of the primary motor cortex. BMC Neurosci 14:64. https://doi.org/10.1186/1471-2202-14-64 CrossRefPubMedPubMedCentralGoogle Scholar
- Sasaki R, Miyaguchi S, Kotan S, Kojima S, Kirimoto H, Onishi H (2016) Modulation of cortical inhibitory circuits after cathodal transcranial direct current stimulation over the primary motor cortex. Front Hum Neurosci 10:30. https://doi.org/10.3389/fnhum.2016.00030 CrossRefPubMedPubMedCentralGoogle Scholar
- Schuck P, Zwingmann C (2003) The ‘smallest real difference’ as a measure of sensitivity to change: a critical analysis. Int J Rehabil Res 26:85–91. https://doi.org/10.1097/01.mrr.0000070759.63544.65 CrossRefPubMedGoogle Scholar
- Silbert BI, Patterson HI, Pevcic DD, Windnagel KA, Thickbroom GW (2013) A comparison of relative-frequency and threshold-hunting methods to determine stimulus intensity in transcranial magnetic stimulation. Clin Neurophysiol 124:708–712. https://doi.org/10.1016/j.clinph.2012.09.018 CrossRefPubMedGoogle Scholar
- Tremblay S, Larochelle-Brunet F, Lafleur LP, El Mouderrib S, Lepage JF, Theoret H (2016) Systematic assessment of duration and intensity of anodal transcranial direct current stimulation on primary motor cortex excitability. Eur J Neurosci 44:2184–2190. https://doi.org/10.1111/ejn.13321 CrossRefPubMedGoogle Scholar
- Zhang X, Woolley DG, Swinnen SP, Feys H, Meesen R, Wenderoth N (2014) Changes in corticomotor excitability and intracortical inhibition of the primary motor cortex forearm area induced by anodal tDCS. PLoS One 9:e101496. https://doi.org/10.1371/journal.pone.0101496 CrossRefPubMedPubMedCentralGoogle Scholar