Showing papers on "Transcranial direct-current stimulation published in 2003"
TL;DR: The selective elimination of tDCS‐driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications and suggests that the after‐effects may be NMDA receptor dependent.
Abstract: Transcranial direct current stimulation (tDCS) of the human motor cortex results in polarity-specific shifts of cortical excitability during and after stimulation. Anodal tDCS enhances and cathodal stimulation reduces excitability. Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation, while cathodal tDCS hyperpolarises cortical neurones. However, not much is known about the ion channels and receptors involved in these effects. Thus, the impact of the sodium channel blocker carbamazepine, the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested. tDCS-protocols inducing excitability alterations (1) only during tDCS and (2) eliciting long-lasting after-effects were applied after drug administration. Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS. Flunarizine resulted in similar changes. Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation, which elicits no after-effects, but prevented the induction of long-lasting after-effects independent of their direction. These results suggest that, like in other animals, cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation, thus modulating the conductance of sodium and calcium channels. Moreover, they suggest that the after-effects may be NMDA receptor dependent. Since NMDA receptors are involved in neuroplastic changes, the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting. The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications.
1,335 citations
TL;DR: It is shown that weak direct currents are capable of improving implicit motor learning in the human and that the primary motor cortex is involved in the acquisition and early consolidation phase of implicit motorlearning.
Abstract: Transcranially applied weak direct currents are capable of modulating motor cortical excitability in the human. Anodal stimulation enhances excitability, cathodal stimulation diminishes it. Cortical excitability changes accompany motor learning. Here we show that weak direct currents are capable of improving implicit motor learning in the human. During performance of a serial reaction time task, the primary motor cortex, premotor, or prefrontal cortices were stimulated contralaterally to the performing hand. Anodal stimulation of the primary motor cortex resulted in increased performance, whereas stimulation of the remaining cortices had no effect. We conclude that the primary motor cortex is involved in the acquisition and early consolidation phase of implicit motor learning.
967 citations
TL;DR: Cathodal transcranial direct current stimulation is capable of inducing prolonged excitability reductions in the human motor cortex non-invasively and these changes are most probably localised intracortically.
704 citations
685 citations
TL;DR: TDCS appears to be a promising tool in neuroplasticity research with some tentative perspectives in clinical neurophysiology, but safe stimulation protocols have to be developed which allow an extension of the duration of after-effects towards a somewhat permanent state.
Abstract: tDCS appears to be a promising tool in neuroplasticity research with some tentative perspectives in clinical neurophysiology. The next steps to be carried out encompass better histological safety data. In order to preclude the possibility of neuronal damage, extending tDCS duration should be limited until more direct safety criteria are available than those derived from Agnew and McCreery (1987) (cf. Nitsche et al, this volume). Safe stimulation protocols have to be developed which allow an extension of the duration of after-effects towards a somewhat permanent state, supposing a beneficial effect can be found in neurological diseases or in neurorehabilitation.
229 citations
TL;DR: The results show that tDCS elicits a transient, reversible excitability alteration of the visual cortex, thus representing a promising tool for neuroplasticity research.
Abstract: Transcranial direct current stimulation (tDCS) can modulate the excitability of the human motor cortex, as revealed by the amplitude of the motor-evoked potentials (MEP). The aim of our study has been to produce localized changes of cerebral excitability of the visual cortex in the intact human by weak anodal and cathodal stimulation. For quantification of current-induced excitability changes, we measured phosphene threshold (PT) using short trains of 5-Hz transcranial magnetic stimulation (TMS) pulses in nine healthy subjects before, immediately after, 10 min, and 20 min after the end of tDCS. PTs are suggested as representative values of visual cortex excitability changes. Reduced PT was detected immediately and 10 min after the end of anodal stimulation, while cathodal stimulation resulted in an opposite effect. Our results show that tDCS elicits a transient, reversible excitability alteration of the visual cortex, thus representing a promising tool for neuroplasticity research.
225 citations
TL;DR: Results show that the excitability shifts induced by V1 stimulation can modulate moving phosphene perception, and tDCS elicits transient, but yet reversible effects, thus presenting a promising tool for neuroplasticity research.
126 citations
TL;DR: It is reported that external DC stimulation over M1 can affect motor consolidation in normal human subjects, leaving the course of learning mostly unchanged, showing that tDCS is evolving into an interesting technique for studying cognition in the human brain.
Abstract: Publisher Summary Cortical excitability can be modulated by constant application of weak electrical currents. Depending on direct current (DC) polarity, neuronal firing rates increase or decrease, presumably due to DC-induced changes of the resting membrane potential. This chapter addresses the question of whether transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) would also affect memory acquisition and consolidation in an explicit motor sequence task. The novel finding reported in this chapter is that external DC stimulation over M1 can affect motor consolidation in normal human subjects, leaving the course of learning mostly unchanged. It has been proposed that the observed effect is due to tDCS-induced prolonged modulation of M1-related neuronal network excitability during the period essential for motor consolidation. It shows that tDCS is evolving into an interesting technique for studying cognition in the human brain.
25 citations
TL;DR: This chapter summarizes results derived from the use of transcranial magnetic stimulation (TMS) and tDCS on visual perception and compares characteristics of the two methods, finding that both techniques are at least partly complementary.
Abstract: Publisher Summary This chapter summarizes results derived from the use of transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) on visual perception and compares characteristics of the two methods. One major aim of vision research is to find methods that are suitable to induce functional changes in the human brain in a controlled, safe way to explore visual perceptual and visuo–cognitive functions. TMS and tDCS allow a manipulation of cortical network activity in humans and in parallel, a psychophysical evaluation of correlated perceptual changes. They influence the brain's activity electrically and change the organized cortical activity transiently and reversibly in a non-invasive, nonpainful way. However, in the mode of action, both techniques are at least partly complementary. TMS is an essential tool in studying the effects of abnormal reorganization of the visual cortex or for examining visual learning effects. TMS and tDCS may elucidate or even modulate plastic changes in the nervous system to influence behavior.
15 citations
TL;DR: It is discussed that the glutamate antagonist riluzole (RLZ) interferes with the capability of the motor cortex to react with excitability changes to transcranial direct current stimulation (tDCS) in a manner similar to the previously tested NMDA receptor blocker DMO.
Abstract: Publisher Summary This chapter discusses that the glutamate antagonist riluzole (RLZ) interferes with the capability of the motor cortex to react with excitability changes to transcranial direct current stimulation (tDCS) in a manner similar to the previously tested NMDA receptor blocker DMO. DMO has been shown to prevent hyperexcitability after anodal as well as hypoexcitability after cathodal tDCS. RLZ is assumed to influence different pre- and postsynaptic processes of glutamate transmission. Different non-glutamatergic actions of RLZ and DMO could be responsible for the dissimilar interference of these drugs with the tDCS after-effects. In addition to the blockade of NMDA receptors, DMO causes a partial inhibition of voltage-dependent calcium and sodium channels. To gain insight into the functionality of tDCS by unravelling receptor and channel effects on the basis of pharmacological interactions with tDCS-induced after-effects has been the major objective of hitherto performed and ongoing pharmacological tDCS studies.
10 citations