***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 OBJECTIVE Recent evidence suggests that fibromyalgia is a disorder characterized by dysfunctional brain activity . Because transcranial direct current stimulation ( tDCS ) can modulate brain activity noninvasively and can decrease pain in patients with refractory central pain , we hypothesized that tDCS treatment would result in pain relief in patients with fibromyalgia . METHODS Thirty-two patients were r and omized to receive sham stimulation or real tDCS with the anode centered over the primary motor cortex ( M1 ) or the dorsolateral prefrontal cortex ( DLPFC ) ( 2 mA for 20 minutes on 5 consecutive days ) . A blinded evaluator rated the patient 's pain , using the visual analog scale for pain , the clinician 's global impression , the patient 's global assessment , and the number of tender points . Other symptoms of fibromyalgia were evaluated using the Fibromyalgia Impact Question naire and the Short Form 36 Health Survey . Safety was assessed with a battery of neuropsychological tests . To assess potential confounders , we measured mood and anxiety changes throughout the trial . RESULTS Anodal tDCS of the primary motor cortex induced significantly greater pain improvement compared with sham stimulation and stimulation of the DLPFC ( P < 0.0001 ) . Although this effect decreased after treatment ended , it was still significant after 3 weeks of followup ( P = 0.004 ) . A small positive impact on quality of life was observed among patients who received anodal M1 stimulation . This treatment was associated with a few mild adverse events , but the frequency of these events in the active-treatment groups was similar to that in the sham group . Cognitive changes were similar in all 3 treatment groups . CONCLUSION Our findings provide initial evidence of a beneficial effect of tDCS in fibromyalgia , thus encouraging further trials Transcranial direct current stimulation ( tDCS ) can up- and down-regulate cortical excitability depending on current direction , however our abilities to measure brain-tissue effects of the stimulation and its after-effects have been limited so far . We used regional cerebral blood flow ( rCBF ) , a surrogate measure of brain activity , to examine regional brain-tissue and brain-network effects during and after tDCS . We varied the polarity ( anodal and cathodal ) as well as the current strength ( 0.8 to 2.0mA ) of the stimulation .  Fourteen healthy subjects were r and omized into receiving either anodal or cathodal stimulation ( two subjects received both , one week apart ) while undergoing Arterial Spin Labeling ( ASL ) in the MRI scanner with an alternating off-on sampling paradigm . The stimulating , MRI-compatible electrode was placed over the right motor region and the reference electrode over the contralateral supra-orbital region . SPM5 was used to process and extract the rCBF data using a 10 mm spherical volume of interest ( VOI ) placed in the motor cortex directly underneath the stimulating scalp electrode . Anodal stimulation induced a large increase ( 17.1 % ) in rCBF during stimulation , which returned to baseline after the current was turned off , but exhibited an increase in rCBF again in the post-stimulation period . Cathodal stimulation induced a smaller increase ( 5.6 % ) during stimulation , a significant decrease compared to baseline ( -6.5 % ) after cessation , and a continued decrease in the post-stimulation period . These changes in rCBF were all significant when compared to the pre-stimulation baseline or to a control region . Furthermore , for anodal stimulation , there was a significant correlation between current strength and the increase in rCBF in the on-period relative to the pre-stimulation baseline . The differential rCBF after-effects of anodal ( increase in resting state rCBF ) and cathodal ( decrease in resting state rCBF ) tDCS support findings of behavioral and cognitive after-effects after cathodal and anodal tDCS . We also show that tDCS not only modulates activity in the brain region directly underlying the stimulating electrode but also in a network of brain regions that are functionally related to the stimulated area . Our results indicate that ASL may be an excellent tool to investigate the effects of tDCS and its stimulation parameters on brain activity OBJECTIVE To investigate in a r and omized , double-blind design , cumulative effects of anodal tDCS on EEG oscillations and neuropsychological tests among patients with traumatic brain injury ( TBI ) undergoing subacute neurorehabilitation . METHODS Twenty-six patients were r and omly assigned to active ( n=13 ) or sham ( n=13 ) tDCS groups .  EEGs  were recorded at 6 different time points , assessing both immediate and cumulative effects of tDCS on EEG oscillations . Twenty minute sessions of 1mA anodal stimulation to the left dorsolateral prefrontal cortex ( F3 , cathode placed at right supraorbital site , Fp2 ) , were provided on 10 consecutive days . Neuropsychological tests were administered before and after the series of tDCS sessions . RESULTS Theta was significantly reduced for active tDCS patients following the first tDCS session . Delta decreased and alpha increased , both significantly , for the active tDCS group after 10 consecutive tDCS sessions . No significant changes were seen for sham group . Decreases in delta were significantly correlated with improved performance on neuropsychological tests for the active tDCS group to far greater degree than for the sham group . Participants in the active tDCS group who had excess slow EEG activity in their initial recordings showed greater improvement on neuropsychological tests than other groups . CONCLUSION Results suggest that 10 anodal tDCS sessions may beneficially modulate regulation of cortical excitability for patients with TBI . SIGNIFICANCE EEG-guided tDCS warrants further investigation as a potential intervention for TBI during subacute neurorehabilitation BACKGROUND The brain-derived neurotrophic factor ( BDNF ) gene is involved in mechanisms of synaptic plasticity in the adult brain . It has been demonstrated that BDNF also plays a significant role in shaping externally induced human brain plasticity . Plasticity induced in the human motor cortex by intermittent theta-burst stimulation ( iTBS ) was impaired in individuals expressing the Val66Met polymorphism . METHODS To explore whether this polymorphism is also important for other neuroplasticity-inducing tools in humans with modes of action differing from that of iTBS , namely , transcranial direct current ( tDCS ) and r and om noise stimulation ( tRNS ) , we retrospectively analyzed the data of 64 subjects studied in our laboratory with regard to BDNF genotype . RESULTS Fifteen subjects with the Val66Met allele , 46 subjects with the Val66Val allele , and 3 Met66Met carriers were identified . The response of the Val66Met allele carriers to stimulation differed in two protocol s compared with the response of Val66Val individuals . For iTBS ( 15 subjects , 5 heterozygotes ) , plasticity could be only induced in the Val66Val allele carriers . However , for facilitatory tDCS ( 24 subjects , 10 heterozygotes ) , as well as for inhibitory tDCS , ( 19 subjects , 8 heterozygotes ) , carriers of the Val66Met allele displayed enhanced plasticity , whereas for transcranial r and om noise stimulation ( 29 subjects , 8 heterozygotes ) , the difference between groups was not so pronounced . CONCLUSIONS BDNF polymorphism has a definite impact on plasticity in humans , which might differ according to the mechanism of plasticity induction . This impact of BDNF on plasticity should be taken into account for future studies , as well as having wider ranging implication s for the treatment of neuropsychiatric disorders with transcranial stimulation tools , as it may predetermine their efficacy for the treatment of disease and rehabilitation Decline in cognitive functions , including impaired acquisition of novel skills , is a feature of older age that impacts activities of daily living , independence , and integration in modern societies The rising proportion of elderly people worldwide will yield an increased incidence of age-associated cognitive impairments , imposing major burdens on societies . Consequently , growing interest emerged to evaluate new strategies to delay or counteract cognitive decline in aging . Here , we assessed immediate effects of anodal transcranial direct current stimulation ( atDCS ) on cognition and previously described detrimental changes in brain activity attributable to aging . Twenty healthy elderly adults were assessed in a crossover sham-controlled design using functional magnetic resonance imaging ( fMRI ) and concurrent transcranial DCS administered to the left inferior frontal gyrus . Effects on performance and task-related brain activity were evaluated during overt semantic word generation , a task that is negatively affected by advanced age . Task-absent resting-state fMRI ( RS-fMRI ) assessed atDCS-induced changes at the network level independent of performance . Twenty matched younger adults served as controls . During sham stimulation , task-related fMRI demonstrated that enhanced bilateral prefrontal activity in older adults was associated with reduced performance . RS-fMRI revealed enhanced anterior and reduced posterior functional brain connectivity .  atDCS significantly improved performance in older adults up to the level of younger controls ; significantly reduced task-related hyperactivity in bilateral prefrontal cortices , the anterior cingulate gyrus , and the precuneus ; and induced a more “ youth-like ” connectivity pattern during RS-fMRI . Our results provide converging evidence from behavioral analysis and two independent functional imaging paradigms that a single session of atDCS can temporarily reverse nonbeneficial effects of aging on cognition and brain activity and connectivity . These findings may translate into novel treatments to ameliorate cognitive decline in normal aging in the future 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 Bihemispheric transcranial direct current stimulation ( tDCS ) is thought to upregulate excitability of the primary motor cortex ( M1 ) using anodal stimulation while concurrently downregulating contralateral M1 using cathodal stimulation . This “ dual ” tDCS method enhances motor learning in healthy subjects and facilitates motor recovery after stroke . However , its impact on motor system activity and connectivity remains unknown . Therefore , we assessed neural correlates of dual and unihemispheric anodal tDCS effects in 20 healthy older subjects in a r and omized , sham-controlled study using a cross-over design . Participants underwent tDCS and simultane 
    Output:
    
Five analyses on moderator variables indicated significant tDCS  beneficial effects : ( a ) on both cognitive and motor task performances , ( b ) across a wide-range of cognitive tasks , ( c ) on specific brain areas , ( d ) stimulation offline ( before ) or online ( during ) the cognitive and motor tasks .