Article

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: 3.75). 04/2008; 27(5):1292-300. DOI: 10.1111/j.1460-9568.2008.06090.x
Source: PubMed

ABSTRACT 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.

0 Bookmarks
 · 
195 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transcranial Direct Current Stimulation (tDCS) is a neuromodulatory device often publicized for its ability to enhance cognitive and behavioral performance. These enhancement claims, however, are predicated upon electrophysiological evidence and descriptions which are far from conclusive. In fact, a review of the literature reveals a number of important experimental and technical issues inherent with this device that are simply not being discussed in any meaningful manner. In this paper, we will consider five of these topics. The first, inter-subject variability, explores the extensive between- and within-group differences found within the tDCS literature and highlights the need to properly examine stimulatory response at the individual level. The second, intra-subject reliability, reviews the lack of data concerning tDCS response reliability over time and emphasizes the importance of this knowledge for appropriate stimulatory application. The third, sham stimulation and blinding, draws attention to the importance (yet relative lack) of proper control and blinding practices in the tDCS literature. The fourth, motor and cognitive interference, highlights the often overlooked body of research that suggests typical behaviors and cognitions undertaken during or following tDCS can impair or abolish the effects of stimulation. Finally, the fifth, electric current influences, underscores several largely ignored variables (such as hair thickness and electrode attachments methods) influential to tDCS electric current density and flow. Through this paper, we hope to increase awareness and start an ongoing dialog of these important issues which speak to the efficacy, reliability, and mechanistic foundations of tDCS.
    Frontiers in Systems Neuroscience 01/2014; 8:2.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Propriospinal neurons (PN) are essential for accurate control of the upper limb, receiving bilateral input from premotor (PM) and primary motor (M1) cortices. In humans, excitability of PNs can be estimated from motor evoked potentials (MEPs) using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation to summate at the C3-C4 level of the spinal cord. Transcranial direct current stimulation (tDCS) alters excitability of cortical and subcortical areas. A recent study demonstrated that cathodal-tDCS can suppress facilitatory (FAC) and inhibitory (INH) components of PN excitability, presumably via effects on cortico-reticulospinal neurons (Bradnam et al., 2011b). The present study investigated the effects of bilateral tDCS with healthy subjects. The cathode was placed over left dorsal PM or M1, and the anode over right M1 in separate sessions (PM-M1, M1-M1 or Sham). TMS of right M1 elicited MEPs in left Biceps Brachii across a range of TMS intensities chosen to examine PN-mediated FAC and INH. Conditioning was applied using median nerve stimulation to coincide with TMS and peripheral volleys summating at the C3-C4 level. All participants showed FAC at TMS intensities near active motor threshold and INH at slightly higher intensities. After tDCS, FAC was reduced for M1-M1 compared to Sham but not after PM-M1 stimulation. Contrary to an earlier study with cathodal-tDCS, INH was unchanged across all sessions. The difference between these and earlier findings may relate to dual vs single hemisphere M1 stimulation. M1-M1 tDCS may be a useful adjuvant to techniques that aim to reduce upper limb impairment after stroke.
    Journal of Neurophysiology 03/2014; · 3.30 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Previous studies have investigated how tDCS over the primary motor cortex modulates excitability in the intrinsic hand muscles. Here, we tested if tDCS changes corticomotor excitability and/or cortical inhibition when measured in the extensor carpi radialis (ECR) and if these aftereffects can be successfully assessed during controlled muscle contraction.
    PLoS ONE 01/2014; 9(7):e101496. · 3.73 Impact Factor

Full-text (2 Sources)

View
39 Downloads
Available from
May 28, 2014