***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 ) 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 UNLABELLED In this study we aim ed to determine current distribution and short-term analgesic effects of transcranial direct current stimulation ( tDCS ) in fibromyalgia using different electrode montages . For each electrode montage , clinical effects were correlated with predictions of induced cortical current flow using magnetic resonance imaging-derived finite element method head model . Thirty patients were r and omized into 5 groups ( Cathodal-M1 [ primary motor cortex ] , Cathodal-SO [ supra-orbital area ] , Anodal-M1 , Anodal-SO , and Sham ) to receive tDCS application ( 2 mA , 20 minutes ) using an extracephalic montage . Pain was measured using a visual numerical scale ( VNS ) , pressure pain threshold ( PPT ) , and a body diagram ( BD ) evaluating pain area . There was significant pain reduction in cathodal-SO and anodal-SO groups indexed by VNS . For PPT there was a trend for a similar effect in anodal-SO group . Computer simulation indicated that the M1-extracephalic montage produced dominantly temporo-parietal current flow , consistent with lack of clinical effects with this montage . Conversely , the SO-extracephalic montage produced current flow across anterior prefrontal structures , thus supporting the observed analgesic effects . Our clinical and modeling findings suggest that electrode montage , considering both electrodes , is critical for the clinical effects of M1-tDCS as electric current needs to be induced in areas associated with the pain matrix . These results should be taken into consideration for the design of pain tDCS studies . PERSPECTIVE Results in this article support that electrode montage is a critical factor to consider for the clinical application of tDCS for pain control , as there is an important correlation between the location of induced electrical current and tDCS-induced analgesic effects Background : Data from the human motor cortex suggest that , depending on polarity , direct current ( DC ) brain polarization can depress or activate cortical neurons . Activating effects on the frontal lobe might be beneficial for patients with frontal lobe disorders . This phase 1 study tested the safety of frontal DC , including its effects on frontal and other brain functions . Methods : The authors applied 20 minutes of anodal , cathodal , or sham DC to the left prefrontal cortex in three groups of right-h and ed subjects and looked for effects on global measures of processing and psychomotor speed , emotion , and verbal fluency , a measure of local cortical function . In one experiment ( n = 30 ) , the authors tested before and after 1 mA DC and monitored EEG in 9 subjects . In two other experiments using 1 mA ( n = 43 ) and 2 mA ( n = 30 ) , the authors tested before and then starting 5 minutes after the onset of DC . Results : All subjects tolerated DC well . There were no significant effects on performance with 1 mA DC . At 2 mA , verbal fluency improved significantly with anodal and decreased mildly with cathodal DC . There were no clinical ly significant effects on the other measures . Conclusions : Limited exposure to direct current polarization of the prefrontal cortex is safe and can enhance verbal fluency selectively in healthy subjects . As such , it deserves consideration as a procedure to improve frontal lobe function in patients Fibromyalgia has been recognized as a central pain disorder with evidence of neuroanatomic and neurophysiologic alterations . Previous studies with techniques of noninvasive brain stimulation -- transcranial direct current stimulation ( tDCS ) and repetitive transcranial magnetic stimulation (rTMS)--have shown that these methods are associated with a significant alleviation of fibromyalgia-associated pain and sleep dysfunction . Here we sought to determine whether a longer treatment protocol involving 10 sessions of 2 mA , 20 min tDCS of the left primary motor ( M1 ) or dorsolateral prefrontal cortex ( DLPFC ) could offer additional , more long-lasting clinical benefits in the management of pain from fibromyalgia . METHODS : Forty-one women with chronic , medically refractory fibromyalgia were r and omized to receive 10 daily sessions of M1 , DLPFC , or sham tDCS . RESULTS : Our results show that M1 and DLPFC stimulation both display improvements in pain scores ( VAS ) and quality of life ( FIQ ) at the end of the treatment protocol , but only M1 stimulation result ed in long-lasting clinical benefits as assessed at 30 and 60 days after the end of treatment . CONCLUSIONS : This study demonstrates the importance of the duration of the treatment period , suggesting that 10 daily sessions of tDCS result in more long lasting outcomes than only five sessions . Furthermore , this study supports the findings of a similarly design ed rTMS trial as both induce pain reductions that are equally long-lasting OBJECTIVE Controlled blinded studies using transcranial electrical stimulation ( tES ) paradigms need a vali date d sham stimulation paradigm since an itching or tingling sensation on the skin surface under the electrode can be associated with current flow . METHODS Here we investigated the skin perception thresholds of transcranial direct current stimulation ( tDCS ) and transcranial r and om noise stimulation ( tRNS ) for current intensities ranging from 200 to 2000μA and additional non-stimulation trials using a motor cortex-contralateral orbit montage in three different healthy subject groups : subjects naïve to tES methods , subjects with previous experience with these techniques and investigators , who use these methods in their research . RESULTS Taking the whole sample into consideration the 50 % perception threshold for both tDCS conditions was at 400μA while this threshold was at 1200μA in the case of tRNS . Anodal and cathodal tDCS are indistinguishable regarding sites of perception . Experienced investigators show a significantly higher anodal stimulation detection rate when compared to the naïve group , furthermore investigators performed significantly better than naïve subjects in non-stimulation discrimination . CONCLUSIONS tRNS has the advantage of higher cutaneous perception thresholds and lower response rates in when compared with tDCS . Further investigation in blinding methods ( such as placebo itching ) is warranted in order to improve sham control . SIGNIFICANCE As tRNS has been shown to have similar aftereffects as anodal tDCS , this finding points to the application of tRNS as a possible alternative with a better blinding control Tinnitus is considered as an auditory phantom percept . Preliminary evidence indicates that transcranial direct current stimulation ( tDCS ) of the temporo-parietal area might reduce  tinnitus .  tDCS studies of the prefrontal cortex have been successful in reducing depression , impulsiveness and pain . Recently , it was shown that the prefrontal cortex is important for the integration of sensory and emotional aspects of tinnitus . As such , frontal tDCS might suppress tinnitus as well . In an open label study , a total of 478 tinnitus patients received bilateral tDCS on dorsolateral prefrontal cortex ( 448 patients anode right , cathode left and 30 anode left , cathode right ) for 20 min . Treatment effects were assessed with visual analogue scale for tinnitus intensity and distress . No tinnitus-suppressing effect was found for tDCS with left anode and right cathode . Analyses show that tDCS with right anode and left cathode modulates tinnitus perception in 29.9 % of the tinnitus patients . For these responders a significant reduction was found for both tinnitus-related distress and tinnitus intensity . In addition , the amount of suppression for tinnitus-related distress is moderated by an interaction between tinnitus type and tinnitus laterality . This was , however , not the case for tinnitus intensity . Our study supports the involvement of the prefrontal cortex in the pathophysiology of tinnitus Preliminary findings suggest that transcranial direct current stimulation ( tDCS ) can have antidepressant effects . We sought to test this further in a parallel-group , double-blind clinical trial with 40 patients with major depression , medication-free r and omized into three groups of treatment : anodal tDCS of the left dorsolateral prefrontal cortex ( active group - ' DLPFC ' ) ; anodal tDCS of the occipital cortex ( active control group - ' occipital ' ) and sham tDCS ( placebo control group - ' sham ' ) . tDCS was applied for 10 sessions during a 2-wk period . Mood was evaluated by a blinded rater using the Hamilton Depression Rating Scale ( HDRS ) and Beck Depression Inventory ( BDI ) . The treatment was well tolerated with minimal side-effects that were distributed equally across all treatment groups . We found significantly larger reductions in depression scores after DLPFC tDCS [ HDRS reduction of 40.4 % ( + /-25.8 % ) ] compared to occipital [ HDRS reduction of 21.3 % ( + /-12.9 % ) ] and sham tDCS [ HDRS reduction of 10.4 % ( + /-36.6 % ) ] . The beneficial effects of tDCS in the DLPFC group persisted for 1 month after the end of treatment . Our findings support further investigation on the effects of this novel potential therapeutic approach - tDCS - for the treatment of major depression In this study , we determined the effects of transcranial electrical stimulation ( TCES ) on the anaesthetic requirements of thiopental and the analgesic requirements of remifentanil , in rats . The experiments were performed on 120 albino male Wistar rats , which were r and omly allocated to four groups ( n=30 ) .  ( Thiopental , Thiopental+TCES , Thiopental+Remifentanil , and Thiopental+Remifentanil+TCES ) . Animals were anaesthetized with thiopental , and 15 min later , remifentanil was injected to rats in the Remifentanil groups . TCES was started in the stimulated groups 20 min after thiopental administration . Rats were stimulated 5 times for this experiment . The times for recovery , herein called Cognition Recovery Time and Motion Recovery Time were measured . Cognition Recovery and Motion Recovery Times were not affected by the stimulation . Analgesia was assessed using the wet tail-flick latency ( TFL ) . In the Thiopental group , the analgesia level returned to control values on the 35th min . In the Thiopental+Remifentanil group , the analgesia level returned to control values on the 50th min . In the Thiopental+ TCES group , the analgesia level reached the peak value on the 65th min . In the Thiopental+Remifentanil+TCES group , the analgesia level reached the peak value on the 35th min and analgesia remained high during the 90 min after cessation of the stimulation . The analgesic potency for the Thiopental+Remifentanil+TCES group was increased by 30 - 40 % when compared with the prior TFL values , 160 % when compared with the control group , and 50 - 75 % when compared with Thiopental+TCES group on the 35th min ( P<0.001 ) . In conclusion , TCES markedly decreases the anaesthetic and analgesic requirements for thiopental and remifentanil in rats PURPOSE To study the effects of cathodal DC polarization in patients with refractory epilepsy and malformations of cortical development ( MCDs ) as indexed by seizure frequency and epileptiform EEG discharges . METHODS Nineteen patients with MCDs and refractory epilepsy underwent one session of DC polarization ( 20 min , 1 mA ) targeting the epileptogenic focus . The number of epileptiform discharges ( EDs ) in the EEG and seizures were measured before ( baseline ) , immediately after , and 15 and 30 days after either sham 
    Output:
    
Nonetheless , almost all studies demonstrated that tDCS had positive immediate and long-lasting effects .