***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 Summary Noninvasive brain stimulation has shown considerable promise for enhancing cognitive functions by the long-term manipulation of neuroplasticity [ 1–3 ] . However , the observation of such improvements has been focused at the behavioral level , and enhancements largely restricted to the performance of basic tasks . Here , we investigate whether transcranial r and om noise stimulation ( TRNS ) can improve learning and subsequent performance on complex arithmetic tasks .  TRNS of the bilateral dorsolateral prefrontal cortex ( DLPFC ) , a key area in arithmetic [ 4 , 5 ] , was uniquely coupled with near-infrared spectroscopy ( NIRS ) to measure online hemodynamic responses within the prefrontal cortex . Five consecutive days of TRNS-accompanied cognitive training enhanced the speed of both calculation- and memory-recall-based arithmetic learning . These behavioral improvements were associated with defined hemodynamic responses consistent with more efficient neurovascular coupling within the left DLPFC . Testing 6 months after training revealed long-lasting behavioral and physiological modifications in the stimulated group relative to sham controls for trained and nontrained calculation material . These results demonstrate that , depending on the learning regime , TRNS can induce long-term enhancement of cognitive and brain functions . Such findings have significant implication s for basic and translational neuroscience , highlighting TRNS as a viable approach to enhancing learning and high-level cognition by the long-term modulation of neuroplasticity Computer-administered cognitive training ( CT ) tasks are a common component of cognitive remediation treatments . There is growing evidence that transcranial direct current stimulation ( tDCS ) , when given during cognitive tasks , improves performance . This r and omized , controlled trial explored the potential synergistic effects of CT combined with tDCS in healthy participants . Altogether , 60 healthy participants were r and omized to receive either active or sham tDCS administered during training on an adaptive CT task ( dual n-back task ) , or tDCS alone , over 10 daily sessions . Cognitive testing ( working memory , processing speed , executive function , reaction time ) was conducted at baseline , end of the 10 sessions , and at 4-wk follow-up to examine potential transfer effects to non-trained tasks . Altogether , 54 participants completed the study . Over the 10 ' online ' sessions , participants in the active tDCS+CT condition performed more accurately on the CT task than participants who received sham tDCS+CT . The performance enhancing effect , however , was present only during tDCS and did not result in greater learning ( i.e. improvement over sessions ) on the CT task . These results confirm prior reports of enhancement of cognitive function during tDCS stimulation . At follow-up , the active tDCS+CT group , but not the sham tDCS+CT group , showed greater gains on a non-trained test of attention and working memory than the tDCS-only group ( p < 0.01 ) . Although this gain can mainly be attributable to training , this result suggests that active tDCS may have a role in further enhancing outcomes The capacity for transcranial direct current stimulation ( tDCS ) to increase learning and cognition shows promise for the development of enhanced therapeutic interventions . One potential application is the combination of tDCS with cognitive training ( CT ) , a psychological intervention which aims to improve targeted cognitive abilities . We have previously shown that tDCS enhanced performance accuracy , but not skill acquisition , on a dual n-back working memory ( WM ) CT task over repeated sessions . In the current study , we investigated the optimal timing for combining tDCS with the same CT task to enhance within and between session performance outcomes across two daily CT sessions . Twenty healthy participants received in a r and omised order 30 min of anodal tDCS to the left dorsolateral prefrontal cortex immediately before ( ‘ offline ’ tDCS ) and during performance ( ‘ online ’ tDCS ) on a dual n-back WM CT task , in an intra-individual crossover design . Analyses examined within and between session consolidation effects of tDCS on CT performance outcomes . Results showed that ‘ online ’ tDCS was associated with better within session skill acquisition on the CT task , with a significant difference found between conditions the following day . These results suggest that ‘ online ’ tDCS is superior to ‘ offline ’ tDCS for enhancing skill acquisition when combining anodal tDCS with CT . This finding may assist with the development of enhanced protocol s involving the combination of tDCS with CT and other rehabilitation protocol The time-dependent effect of transcranial direct current stimulation ( tDCS ) on working memory was investigated by applying anodal stimulation over the left prefrontal cortex . This single-blind , sham-controlled crossover study recruited 15 healthy participants . A three-back verbal working-memory task was performed before , during , and 30 min after 1 mA anodal or sham tDCS . Anodal tDCS , compared with sham stimulation , significantly improved working-memory performance . Accuracy of response was significantly increased after 20 min of tDCS application , and was further enhanced after 30 min of stimulation . This effect was maintained for 30 min after the completion of stimulation . These results suggest that tDCS at 1 mA enhances working memory in a time-dependent manner for at least 30 min in healthy participants Weak transcranial direct current stimulation ( tDCS ) induces persisting excitability changes in the human motor cortex . These plastic excitability changes are selectively controlled by the polarity , duration and current strength of stimulation . To reveal the underlying mechanisms of direct current (DC)-induced neuroplasticity , we combined tDCS of the motor cortex with the application of Na(+)-channel-blocking carbamazepine ( CBZ ) and the N-methyl-D-aspartate (NMDA)-receptor antagonist dextromethorphan ( DMO ) . Monitored by transcranial magnetic stimulation ( TMS ) , motor cortical excitability changes of up to 40 % were achieved in the drug-free condition . Increase of cortical excitability could be selected by anodal stimulation , and decrease by cathodal stimulation . Both types of excitability change lasted several minutes after cessation of current stimulation . DMO suppressed the post-stimulation effects of both anodal and cathodal DC stimulation , strongly suggesting the involvement of NMDA receptors in both types of DC-induced neuroplasticity . In contrast , CBZ selectively eliminated anodal effects . Since CBZ stabilizes the membrane potential voltage-dependently , the results reveal that after-effects of anodal tDCS require a depolarization of membrane potentials . Similar to the induction of established types of short- or long-term neuroplasticity , a combination of glutamatergic and membrane mechanisms is necessary to induce the after-effects of tDCS . On the basis of these results , we suggest that polarity-driven alterations of resting membrane potentials represent the crucial mechanisms of the DC-induced after-effects , leading to both an alteration of spontaneous discharge rates and to a change in NMDA-receptor activation BACKGROUND Major depressive disorder ( MDD ) is frequently associated with underactivity of the dorsolateral prefrontal cortex ( DLPFC ) which has led to this brain region being identified as an important target for the development of neurobiological treatments . Transcranial direct current stimulation ( tDCS ) administered to the DLPFC has antidepressant efficacy , however the magnitude of antidepressant outcomes are limited . Concurrent cognitive activity has been shown to enhance tDCS induced stimulation effects . Cognitive control training ( CCT ) is a new cognitive therapy for MDD that aims to enhance DLPFC activity via behavioral methods . HYPOTHESIS We tested the hypothesis that co-administration of DLPFC tDCS and CCT would result in a greater reduction in depressive symptomology than administration of tDCS or CCT alone . METHODS 27 adult participants with MDD were r and omized into a three-arm sham-controlled between-groups pilot study comparing the efficacy of 2 mA tDCS + CCT , sham tDCS + CCT and sham CCT + 2 mA tDCS ( 5 sessions administered on consecutive working days ) . Blinded assessment s of depression severity and cognitive control were conducted at baseline , end of treatment and a three week follow up review . RESULTS All three treatment conditions were associated with a reduction in depression severity at the end of five treatment sessions . However , only administration of tDCS + CCT result ed in sustained antidepressant response at follow up , the magnitude of which was greater than that observed immediately following conclusion of the treatment course . CONCLUSIONS The results provide preliminary evidence that concurrent CCT enhances antidepressant outcomes from tDCS . In the current sample , participants receiving concurrent tDCS and CCT continued to improve following cessation of treatment . The clinical superiority of a combined therapeutic approach was apparent even in a small sample and following a relatively short treatment course Improvement in performance following cognitive training is known to be further enhanced when coupled with brain stimulation . Here we ask whether training-induced changes can be maintained long term and , crucially , whether they can extend to other related but untrained skills . We trained overall 40 human participants on a simple and well established paradigm assessing the ability to discriminate numerosity – or the number of items in a set – which is thought to rely on an “ approximate number sense ” ( ANS ) associated with parietal lobes . We coupled training with parietal stimulation in the form of transcranial r and om noise stimulation ( tRNS ) , a noninvasive technique that modulates neural activity . This yielded significantly better and longer lasting improvement ( up to 16 weeks post-training ) of the precision of the ANS compared with cognitive training in absence of stimulation , stimulation in absence of cognitive training , and cognitive training coupled to stimulation to a control site ( motor areas ) . Critically , only ANS improvement induced by parietal tRNS + Training transferred to proficiency in other parietal lobe-based quantity judgment , i.e. , time and space discrimination , but not to quantity-unrelated tasks measuring attention , executive functions , and visual pattern recognition . These results indicate that coupling intensive cognitive training with tRNS to critical brain regions result ed not only in the greatest and longer lasting improvement of numerosity discrimination , but importantly in this enhancement being transferable when trained and untrained abilities are carefully chosen to share common cognitive and neuronal components Non-invasive electrical stimulation of the human cortex by means of transcranial direct current stimulation ( tDCS ) has been instrumental in a number of important discoveries in the field of human cortical function and has become a well-established method for evaluating brain function in healthy human participants . Recently , transcranial alternating current stimulation ( tACS ) has been introduced to directly modulate the ongoing rhythmic brain activity by the application of oscillatory currents on the human scalp . Until now the efficiency of tACS in modulating rhythmic brain activity has been indicated only by inference from perceptual and behavioural consequences of electrical stimulation . No direct electrophysiological evidence of tACS has been reported . We delivered tACS over the occipital cortex of 10 healthy participants to entrain the neuronal oscillatory activity in their individual alpha frequency range and compared results with those from a separate group of participants receiving sham stimulation . The tACS but not the sham stimulation elevated the endogenous alpha power in parieto- central electrodes of the electroencephalogram . Additionally , in a network of spiking neurons , we simulated how tACS can be affected even after the end of stimulation . The results show that spike-timing-dependent plasticity ( STDP ) selectively modulates synapses depending on the resonance frequencies of the neural circuits that they belong to . Thus , tACS  influences STDP which in turn results in aftereffects upon neural activity . The present findings are the first direct electrophysiological evidence of an interaction of tACS and ongoing oscillatory activity in the human cortex . The data demonstrate the ability of tACS to specifically modulate oscillatory brain activity and show its potential both at fostering knowledge on the functional significance of brain oscillations and for therapeutic application Perceptual learning is considered a manifestation of neural plasticity 
    Output:
    
Findings indicated that tES + CT enhanced performance on the majority of CT tasks .
The effects on non-trained tasks were mixed , with some evidence for improvements in working memory , cognitive control , approximate number sense and arithmetic processing .
tES + CT enhances performance on CT tasks across a range of cognitive functions .
Preliminary evidence suggests that tES may also increase transfer effects to non-trained tasks in some domains .