Antal A, Boros K, Poreisz C, Chaieb L, Terney D, Paulus W. Comparatively weak after-effects of transcranial alternating current stimulation (tACS) on cortical excitability in humans. Brain Stimul. 2008;1(2):97-105

Department of Clinical Neurophysiology, Georg-August University, Göttingen, Germany.
Brain Stimulation (Impact Factor: 5.43). 04/2008; 1(2):97-105. DOI: 10.1016/j.brs.2007.10.001
Source: PubMed

ABSTRACT Interference with brain rhythms by noninvasive transcranial stimulation that uses weak transcranial alternating current may reveal itself to be a new tool for investigating cortical mechanisms currently unresolved. Here, we aim to extend transcranial direct current stimulation (tDCS) techniques to transcranial alternating current stimulation (tACS).
Parameters such as electrode size and position were taken from those used in previous tDCS studies.
Motor evoked potentials (MEPs) revealed by transcranial magnetic stimulation (TMS), electroencephalogram (EEG)-power, and reaction times measured in a motor implicit learning task, were analyzed to detect changes in cortical excitability after 2-10 minutes of AC stimulation and sinusoidal DC stimulation (tSDCS) by using 1, 10, 15, 30, and 45 Hz and sham stimulation over the primary motor cortex in 50 healthy subjects (eight-16 subjects in each study).
A significantly improved implicit motor learning was observed after 10 Hz AC stimulation only. No significant changes were observed in any of the analyzed frequency bands of EEG and with regard to the MEP amplitudes after AC or tSDCS stimulation. Similarly, if the anodal or cathodal DC stimulation was superimposed on 5, 10, and 15 Hz AC stimulation, the MEP amplitudes did not change significantly.
Transcranial application of weak AC current may appear to be a tool for basic and clinical research in diseases with altered EEG activity. However, its effect seems to be weaker than tDCS stimulation, at least in the present context of stimulus intensity and duration. Further studies are required to extend cautiously the safety range and uncover its influence on neuronal circuitries.

1 Follower
  • Source
    • "Although a subjective measure, the threshold for evoking phosphenes can be reliably measured and changes in the threshold for evoking phosphenes provides an indication of changes in the excitability (plasticity) of the visual cortex (Cowey & Walsh, 2000; Pascual-Leone & Walsh, 2001). Modulations in phosphene threshold have been observed following application of rTMS to the occipital cortex (likely V1/V2), and modulations in the direction of moving phosphenes evoked by TMS to the motion-selective area V5 have been observed following visual motion adaptation (Antal et al., 2002; Boroojerdi, Prager, Muellbacher, & Cohen, 2000; Cattaneo & Silvanto, 2008; Guzman-Lopez, Silvanto, & Seemungal, 2011; Ray, Meador, Epstein, Loring, & Day, 1998). Secondly, it is possible to investigate plasticity induction by quantifying changes in evoked potentials generated in the target cortical region. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The last couple of decades have seen the development of a number of non-invasive brain stimulation (NIBS) techniques that are capable of inducing short-lasting plasticity in the human cortex. Importantly, the induction of lasting plastic changes can, under some conditions, reversibly modify behaviour and interact with learning. These techniques have provided novel opportunities to study human cortical plasticity and examine the role of cortical regions in behaviour. In this review we briefly summarise current NIBS techniques, outline approaches to characterise and quantify cortical plastic change, and describe mechanisms that are implicated in the induced plastic changes. We then outline the areas in which these techniques might be useful, namely, investigating the mechanisms of human cortical plasticity, the characterisation of influences on plasticity, and the investigation of the role of cortical regions in behaviour. Finally, we conclude by highlighting some current limitations of the techniques and suggest that further development of the current NIBS paradigms and more focussed targeting should further enhance the utility of these powerful non-invasive techniques for the investigation of the cortical plasticity and pathophysiology.
    Cortex 09/2014; DOI:10.1016/j.cortex.2013.12.006 · 6.04 Impact Factor
  • Source
    • "In tRNS the areas underneath both electrodes are stimulated with a current whose amplitude varies randomly in time within the frequency range of 100–640 Hz (Terney et al., 2008; Ruffini et al., 2013). In tACS, an alternating current (AC) with a pre-determined frequency passes from anodal to cathodal and the frequency is usually set within the EEG frequency spectrum (1–100 Hz) (Antal et al., 2008; Kanai et al., 2010). The protocol for tCS stimulation, especially the anodal and cathodal electrodes location, is usually determined based on neuroimaging findings (e.g., EEG, fMRI) evidencing that a certain region is involved in the target brain function which the researcher wants to modulate. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Transcranial current brain stimulation (tCS) is becoming increasingly popular as a non-pharmacological non-invasive neuromodulatory method that alters cortical excitability by applying weak electrical currents to the scalp via a pair of electrodes. Most applications of this technique have focused on enhancing motor and learning skills, as well as a therapeutic agent in neurological and psychiatric disorders. In these applications, similarly to lesion studies, tCS was used to provide a causal link between a function or behaviour and a specific brain region (e.g., primary motor cortex). Nonetheless, complex cognitive functions are known to rely on functionally connected multitude of brain regions with dynamically changing patterns of information flow rather than on isolated areas, which are most commonly targeted in typical tCS experiments. In this review article, we argue in favour of combining tCS method with other neuroimaging techniques (e.g. fMRI, EEG) and by employing state-of-the-art connectivity data analysis techniques (e.g. graph theory) to obtain a deeper understanding of the underlying spatiotemporal dynamics of functional connectivity patterns and cognitive performance. Finally, we discuss the possibilities of these combined techniques to investigate the neural correlates of human creativity and to enhance creativity.
    Frontiers in Systems Neuroscience 07/2014; 8. DOI:10.3389/fnsys.2014.00132
  • Source
    • "contraction, through membrane depolarization and stimulation of muscle nerve (Antal et al., 2008). At high frequency (HF) (greater than 3 MHz), thermal effects due to induced high-frequency electric field will be the constituent phenomenon in the tissues (Miklavcic et al., 2005; Z ˇ upanič et al., 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Electrical properties of the cells play a key role in biological processes. Intermediate frequencies of electrical fields influence the cells proliferation without heat generation and electrical stimulation. Silver nanoparticle (SNP) as a metallic agent can change the electrical characteristics of the cells. We study the effect of low voltages at an intermediate frequency (300 kHz) on a human breast adenocarcinoma cell line (MCF7) in the presence of SNPs. At first, cell toxicity of SNPs was determined at different concentrations. Then three different voltages were applied to the cells for 15 min, both in the presence and absence of SNPs. The treatments efficiency was evaluated by MTT assay. The results showed that the intermediate frequency-low voltages with SNPs not only provide an additive efficacy on cytotoxicity, but also a synergism was observed between these factors. By increasing the voltage from 3 to 9 V, a rising synergistic rate was observed. It seems that the synergistic effect between SNPs and the 300 kHz low voltages can inhibit cell proliferation and/or increases cell death of MCF-7, and hence increases treatment efficiency of SNPs, effectively.
    Electromagnetic Biology and Medicine 06/2014; DOI:10.3109/15368378.2014.919590 · 0.77 Impact Factor
Show more