Premotor transcranial direct current stimulation (tDCS) affects primary motor excitability in humans

Department of Clinical Neurophysiology, Georg-August University, Robert Koch Strasse 40, 37075 Göttingen, Germany.
European Journal of Neuroscience (Impact Factor: 3.18). 04/2008; 27(5):1292-300. DOI: 10.1111/j.1460-9568.2008.06090.x
Source: PubMed


Recent studies have shown that repetitive transcranial magnetic stimulation (rTMS) over the premotor cortex (PM) modifies the excitability of the ipsilateral primary motor cortex (M1). Transcranial direct current stimulation (tDCS) is a new method to induce neuroplasticity in humans non-invasively. tDCS generates neuroplasticity directly in the cortical area under the electrode, but might also induce effects in distant brain areas, caused by activity modulation of interconnected areas. However, this has not yet been tested electrophysiologically. We aimed to study whether premotor tDCS can modify the excitability of the ipsilateral M1 via cortico-cortical connectivity. Sixteen subjects received cathodal and anodal tDCS of the PM and eight subjects of the dorsolateral prefrontal cortex. Premotor anodal, but not premotor cathodal or prefrontal tDCS, modified selectively short intracortical inhibition/intracortical facilitation (SICI/ICF), while motor thresholds, single test-pulse motor-evoked potential and input-output curves were stable throughout the experiments. Specifically, anodal tDCS decreased intracortical inhibition and increased paired-pulse excitability. The selective influence of premotor tDCS on intracortical excitability of the ipsilateral M1 suggests a connectivity-driven effect of tDCS on remote cortical areas. Moreover, this finding indirectly substantiates the efficacy of tDCS to modulate premotor excitability, which might be of interest for applications in diseases accompanied by pathological premotor activity.

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Available from: Michael A Nitsche, Oct 09, 2015
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    • "It is possible that the effects of tDCS over PM were mediated by a stimulation-evoked increase in M1 excitability, which has been shown to contain neurons with mirrorlike properties in non-human primates (Tkach et al., 2007; Dushanova & Donoghue, 2010) and so may be engaged in observational as well as active motor learning. Although anodal tDCS over PM does not affect overall M1 excitability assessed by TMS thresholds for motor-evoked potentials or by TMS input/output functions, it does decrease short-interval intracortical inhibition and increase intracortical facilitation in M1, effects argued to result from activation of physiological connections from PM to M1 (Boros et al., 2008). "
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    ABSTRACT: Motor skills, including complex movement sequences, can be acquired by observing a model without physical practice of the skill, a phenomenon known as observational learning. Observational learning of motor skills engages the same memory substrate as physical practice, and is thought to be mediated by the action observation network, a bilateral fronto-parietal circuit with mirror-like properties. We examined the effects of anodal tDCS over premotor cortex, a key node of the action observation network, with on observational learning of a serial response time task. Results showed that anodal tDCS during observation of the to-be-learned sequence facilitated reaction times in the subsequent behavioral test. The study provides evidence that increasing excitability of the AON during observation can facilitate later motor skill acquisition. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    European Journal of Neuroscience 04/2015; 41(12). DOI:10.1111/ejn.12916 · 3.18 Impact Factor
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    • "The primary effect is a polaritydependent shift in resting membrane potentials, and sufficiently long stimulation results in long-lasting excitability enhancements or reductions which depend on the glutamatergic and GABAergic systems (Nitsche & Paulus, 2001, 2011; Nitsche et al., 2003a,b, 2005; Stagg et al., 2009). tDCS is suited to the exploration of plasticity of interregional cortical connectivity, as shown by its ability to induce plasticity of premotor–motor cortex connections (Boros et al., 2008), and has been shown to improve motor learning (Nitsche et al., 2003c; Reis et al., 2009). We hypothesized that excitabilityenhancing anodal tDCS applied to the posterior parietal cortex (P3) will enhance M1 excitability, while cathodal tDCS over the same area will result in antagonistic effects. "
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    ABSTRACT: The posterior parietal cortex is part of the cortical network involved in motor learning and is structurally and functionally connected with the primary motor cortex (M1). Neuroplastic alterations of neuronal connectivity might be an important basis for learning processes. These have however not been explored for parieto-motor connections in humans by transcranial direct current stimulation (tDCS). Exploring tDCS effects on parieto-motor cortical connectivity might be functionally relevant, because tDCS has been shown to improve motor learning. We aimed to explore plastic alterations of parieto-motor cortical connections by tDCS in healthy humans. We measured neuroplastic changes of corticospinal excitability via motor evoked potentials (MEP) elicited by single-pulse transcranial magnetic stimulation (TMS) before and after tDCS over the left posterior parietal cortex (P3), and 3 cm posterior or lateral to P3, to explore the spatial specificity of the effects. Furthermore, short-interval intracortical inhibition/intracortical facilitation (SICI/ICF) over M1, and parieto-motor cortical connectivity were obtained before and after P3 tDCS. The results show polarity-dependent M1 excitability alterations primarily after P3 tDCS. Single-pulse TMS-elicited MEPs, M1 SICI/ICF at 5 and 7 ms and 10 and 15 ms interstimulus intervals (ISIs), and parieto-motor connectivity at 10 and 15 ms ISIs were all enhanced by anodal stimulation. Single pulse-TMS-elicited MEPs, and parieto-motor connectivity at 10 and 15 ms ISIs were reduced by cathodal tDCS. The respective corticospinal excitability alterations lasted for at least 120 min after stimulation. These results show an effect of remote stimulation of parietal areas on M1 excitability. The spatial specificity of the effects and the impact on parietal cortex-motor cortex connections suggest a relevant connectivity-driven effect. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.
    European Journal of Neuroscience 02/2015; 41(6). DOI:10.1111/ejn.12840 · 3.18 Impact Factor
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    • "TDCS is in wide use in clinical populations such as stroke (Fregni et al., 2005; Hummel et al., 2005; Boggio et al., 2007b; Jo et al., 2009; Kang et al., 2009; Baker et al., 2010; Lindenberg et al., 2010; Chrysikou and Hamilton, 2011; Hamilton et al., 2011), Parkinson's (Boggio et al., 2006; Fregni et al., 2006c), Alzheimer's (Boggio et al., 2011, 2012), depression (Fregni et al., 2006b; Ferrucci et al., 2009; Loo et al., 2010; Kalu et al., 2012), and chronic pain (Fregni et al., 2006a; Lefaucheur et al., 2008). It is also applied to healthy participants in cognitive domains such as working memory (WM) (Marshall et al., 2005; Ohn et al., 2008; Berryhill et al., 2010; Andrews et al., 2011; Mulquiney et al., 2011; Berryhill and Jones, 2012; Jeon and Han, 2012; Jones and Berryhill, 2012; Hoy et al., 2013), episodic memory (Ross et al., 2010, 2011; Javadi and Walsh, 2012; Javadi and Cheng, 2013), perception (Antal et al., 2001, 2003, 2004, 2006; Antal and Paulus, 2008; Bachmann et al., 2010; Bolognini et al., 2011; Borckardt et al., 2012), and motor processing (Nitsche et al., 2005, 2007; Boros et al., 2008; Hunter et al., 2009; Antal et al., 2011). "
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    ABSTRACT: The popularity of non-invasive brain stimulation techniques in basic, commercial, and applied settings grew tremendously over the last decade. Here, we focus on one popular neurostimulation method: transcranial direct current stimulation (tDCS). Many assumptions regarding the outcomes of tDCS are based on the results of stimulating motor cortex. For instance, the primary motor cortex is predictably suppressed by cathodal tDCS or made more excitable by anodal tDCS. However, wide-ranging studies testing cognition provide more complex and sometimes paradoxical results that challenge this heuristic. Here, we first summarize successful efforts in applying tDCS to cognitive questions, with a focus on working memory (WM). These recent findings indicate that tDCS can result in cognitive task improvement or impairment regardless of stimulation site or direction of current flow. We then report WM and response inhibition studies that failed to replicate and/or extend previously reported effects. From these opposing outcomes, we present a series of factors to consider that are intended to facilitate future use of tDCS when applied to cognitive questions. In short, common pitfalls include testing too few participants, using insufficiently challenging tasks, using heterogeneous participant populations, and including poorly motivated participants. Furthermore, the poorly understood underlying mechanism for long-lasting tDCS effects make it likely that other important factors predict responses. In conclusion, we argue that although tDCS can be used experimentally to understand brain function its greatest potential may be in applied or translational research.
    Frontiers in Psychology 07/2014; 5:800. DOI:10.3389/fpsyg.2014.00800 · 2.80 Impact Factor
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