***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Transcranial direct current stimulation ( tDCS ) was recently reintroduced as a tool for inducing relatively long-lasting changes in cortical excitability in focal brain regions . Anodal stimulation over the primary motor cortex enhances cortical excitability , whereas cathodal stimulation decreases it . Prior studies have shown that enhancement of D2 receptor activity by pergolide consoli date s tDCS-generated excitability diminution for up to 24 hours and that cathodal stimulation of the primary motor cortex diminishes experimentally induced pain sensation and reduces the N2-P2 amplitude of laser-evoked potentials immediately poststimulation . In the present study , we investigated the effect of pergolide and cathodal tDCS over the primary motor cortex on laser-evoked potentials and acute pain perception induced with a Tm : YAG laser in a double-blind , r and omized , placebo-controlled , crossover study . The amplitude changes of laser-evoked potentials and subjective pain rating scores of 12 healthy subjects were analyzed prior to and following 15 minutes cathodal tDCS combined with pergolide or placebo intake at five different time points . Our results indicate that the amplitude of the N2 component was significantly reduced following cathodal tDCS for up to two hours . Additionally , pergolide prolonged the effect of the cathodal tDCS for up to 24 hours , and a significantly lowered pain sensation was observed for up to 40 minutes . Our study is a further step toward clinical application of cathodal tDCS over the primary motor cortex using pharmacological intervention to prolong the excitability-diminishing effect on pain perception for up to 24 hours poststimulation . Furthermore , it demonstrates the potential for repetitive daily stimulation therapy for pain patients 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- protocol s 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 result ed 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 Background Preventive pharmacotherapy for migraine is not satisfactory because of the low efficacy/tolerability ratio of many available drugs . Novel and more efficient preventive strategies are therefore warranted . Abnormal excitability of cortical areas appears to play a pivotal role in migraine pathophysiology . Transcranial direct current stimulation ( tDCS ) is a non-invasive and safe technique that is able to durably modulate the activity of the underlying cerebral cortex , and is being tested in various medical indications . The results of small open studies using tDCS in migraine prophylaxis are conflicting , possibly because the optimal stimulation setting s and the brain targets were not well chosen . We have previously shown that the cerebral cortex , especially the visual cortex , is hyperresponsive in migraine patients between attacks and provided evidence from evoked potential studies that this is due to a decreased cortical preactivation level . If one accepts this concept , anodal tDCS over the visual cortex may have therapeutic potentials in migraine prevention , as it is able to increase neuronal firing . Objective To study the effects of anodal tDCS on visual cortex activity in healthy volunteers ( HV ) and episodic migraine without aura patients ( MoA ) , and its potentials for migraine prevention . Methods We recorded pattern-reversal visual evoked potentials ( VEP ) before and after a 15-min session of anodal tDCS over the visual cortex in 11 HV and 13 MoA interictally . Then 10 MoA patients reporting at least 4 attacks/month subsequently participated in a therapeutic study , and received 2 similar sessions of tDCS per week for 8 weeks as migraine preventive therapy . Results In HV as well as in MoA , anodal tDCS transiently increased habituation of the VEP N1P1 component . VEP amplitudes were not modified by tDCS . Preventive treatment with anodal tDCS turned out to be beneficial in MoA : migraine attack frequency , migraine days , attack duration and acute medication intake significantly decreased during the treatment period compared to pre-treatment baseline ( all p < 0.05 ) , and this benefit persisted on average 4.8 weeks after the end of tDCS . Conclusions Anodal tDCS over the visual cortex is thus able to increase habituation to repetitive visual stimuli in healthy volunteers and in episodic migraineurs , who on average lack habituation interictally . Moreover , 2 weekly sessions of anodal tDCS had a significant preventive anti- migraine effect , proofing the concept that the low preactivation level of the visual cortex in migraine patients can be corrected by an activating neurostimulation . The therapeutic results indicate that a larger sham-controlled trial using the same tDCS protocol is worthwhile Transcranial DC stimulation ( tDCS ) is a plasticity-inducing noninvasive brain stimulation tool with various potential therapeutic applications in neurological and psychiatric diseases . Currently , the duration of the aftereffects of stimulation is restricted . For future clinical applications , stimulation protocol s are required that produce aftereffects lasting for days or weeks . Options to prolong the effects of tDCS are further prolongation or repetition of tDCS . Nothing is known thus far about optimal protocol s in this behalf , although repetitive stimulation is already performed in clinical applications . Thus we explored the effects of different break duration s on cathodal tDCS-induced cortical excitability alterations . In 12 subjects , two identical periods of cathodal tDCS ( 9-min duration ; 1 mA ) with an interstimulation interval of 0 ( no break ) , 3 , or 20 min or 3 or 24 h were performed . The results indicate that doubling stimulation duration without a break prolongs the aftereffects from 60 to 90 min after tDCS . When the second stimulation was performed during the aftereffects of the first , a prolongation and enhancement of tDCS-induced effects for ≤ 120 min after stimulation was observed . In contrast , when the second stimulation followed the first one after 3 or 24 h , the aftereffects were initially attenuated , or abolished , but afterwards re-established for up to 120 min after tDCS in the 24-h condition . These results suggest that , for prolonging the aftereffects of cathodal tDCS , stimulation interval might be important Voluntarily modulating neural activity plays a key role in brain-computer interface ( BCI ) . In general , the self-regulated neural activation patterns are used in the current BCI systems involving the repetitive trainings with feedback for an attempt to achieve a high- quality control performance . With the limitation posed by the training procedure in most BCI studies , the present work aims to investigate whether directly modulating the neural activity by using an external method could facilitate the BCI control . We design ed an experimental paradigm that combines anodal transcranial direct current stimulation ( tDCS ) with a motor imagery (MI)-based feedback EEG BCI system .  Thirty-two young and healthy human subjects were r and omly assigned to the real and sham stimulation groups to evaluate the effect of tDCS-induced EEG pattern changes on BCI classification accuracy . Results showed that the anodal tDCS obviously induces sensorimotor rhythm (SMR)-related event-related desynchronization ( ERD ) pattern changes in the upper-mu ( 10 - 14 Hz ) and beta ( 14 - 26 Hz ) rhythm components . Both the online and offline BCI classification results demonstrate that the enhancing ERD patterns could conditionally improve BCI performance . This pilot study suggests that the tDCS is a promising method to help the users to develop reliable BCI control strategy in a relatively short time PURPOSE Transcranial direct current stimulation ( tDCS ) has proven to be a useful tool for fundamental brain research as well as for attempts in therapy of neurological and psychiatric diseases by modulating neuronal plasticity . Little is understood about the effects of tDCS are influenced by hemispheric dominance , even less in terms of h and edness . The aim of our pilot study was to investigate whether tDCS induced neuroplastic changes may be different in right- and left-h and ed individuals due to existing differences in hemispheric lateralisation . METHODS We measured changes in motor evoked potentials ( MEPs ) after application of tDCS in 8 right-h and ers , 8 left-h and ers and 8 mixed-h and ers according to the Edinburgh H and edness Inventory ( EHI ) . In double-blind sessions , we applied either anodal or cathodal tDCS for 5 minutes for each hemisphere . RESULTS While motor thresholds ( MT ) seem to be not influenced by h and edness significantly , in right-h and ed subjects we reproduced the well-known effects of  tDCS :  anodal stimulation increased while cathodal stimulation decreased MEP amplitudes . However , left- and mixed-h and ed subjects differed from right-h and ed subjects . After anodal stimulation of the left hemisphere the increase of the MEP amplitudes was stronger in right h and ed subjects than in left and mixed h and ed subjects . Interestingly , after cathodal stimulation of the left hemisphere this difference was less marked . The stimulation of the right hemisphere showed the same tendency , but results were not significant . CONCLUSIONS For the first time , we are able to demonstrate that the modulating effects of tDCS on corticospinal excitability differ moderately in the left- and mixed-h and ed population compared to right-h and ed subjects . The shown differences according to h and edness should be taken into account in further studies Low-level direct currents ( DC ) are thought to polarize brain tissue and to affect brain processes . The present experiments investigated the effects of low-level transcortical DC-currents on response speed and physiological variables in humans . The DC-currents were applied during the warning interval within a constant foreperiod reaction time paradigm . Currents of less than 0.3 mA were applied between a vertex electrode and a noncephalic reference . The polarity of the electrical source varied r and omly across trials within subjects . The first two studies showed that subjects  respond fastest when the positive pole is applied to the vertex . Under the same conditions higher skin conductance responses were observed as compared to vertex negative conditions . The dynamics of the observed responses suggest that the brain " learns " to respond differentially to the different current polarities . This was confirmed by the third study , which documented different conditioned electroencephalic responses subsequent to current application Transcranial direct current stimulation ( tDCS ) over the primary motor cortex ( M1 ) has been shown to induce changes in motor performance and learning . Recent studies indicate that tDCS is capable of modulating widespread neural network properties within the brain . However the temporal evolution of online- and after-effects of tDCS on functional connectivity ( FC ) within and across the stimulated motor cortices ( M1 ) still remain elusive . In the present study , two different tDCS setups were investigated : ( i ) unilateral M1 tDCS ( anode over right M1 , cathode over the contralateral supraorbital region ) and ( ii ) bilateral M1 tDCS ( anode over right M1 , cathode over left M1 ) . In a r and omized single-blinded cross-over design , 12 healthy subjects underwent functional magnetic resonance imaging at rest before , during and after 20 min of either bi- , unilateral , or sham M1 tDCS . Seed-based FC analysis was used to investigate tDCS-induced changes across and within M1 . We found that bilateral M1 tDCS induced ( a ) a decrease in interhemispheric FC during stimulation and ( b ) an increase in intracortical FC within right M1 after termination of the intervention . While unilateral M1 tDCS also result ed in similar effects during stimulation , no such changes could be observed after termination of tDCS . Our results provide evidence that depending on the electrode montage , tDCS acts upon a modulation of either intracortical and /or interhemispheric processing of M1 In recent years , two techniques have become available for the non-invasive stimulation of human motor cortex : transcranial magnetic stimulation ( TMS ) and transcranial direct current stimulation ( tDCS ) . The effects of TMS and tDCS when applied over motor cortex should be considered with regard not only to cortical circuits but also to spinal motor circuits . The different modes of action and specificity of TMS and tDCS suggest that their effects 
    Output:
    
RESULTS Of the 30 neurophysiological outcome measures reported by at least two different research groups , tDCS was found to have a reliable effect on only one : MEP amplitude .
Interestingly , the magnitude of this effect has been significantly decreasing over the last 14 years .