***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 ) uses a weak electric current to modulate neuronal activity . A neurophysiologic outcome measure to demonstrate reliable tDCS modulation at the group level is transcranial magnetic stimulation engendered motor evoked potentials ( MEPs ) . Here , we conduct a study testing the reliability of individual MEP response patterns following a common tDCS protocol . Fourteen participants ( 7m/7f ) each underwent nine r and omized sessions of 1 mA , 10 min tDCS ( 3 anode ; 3 cathode ; 3 sham ) delivered using an M1/orbito-frontal electrode montage ( sessions separated by an average of ~5.5 days ) . Fifteen MEPs were obtained prior to , immediately following and in 5 min intervals for 30 min following tDCS . TMS was delivered at 130 % resting motor threshold using neuronavigation to ensure consistent coil localization . A number of non-experimental variables were collected during each session . At the individual level , considerable variability was seen among different testing sessions . No participant demonstrated an excitatory response ≥20 % to all three anodal sessions , and no participant demonstrated an inhibitory response ≥20 % to all three cathodal sessions . Intra-class correlation revealed poor anodal and cathodal test – retest reliability [ anode : ICC(2,1 ) = 0.062 ; cathode : ICC(2,1 ) = 0.055 ] and moderate sham test – retest reliability [ ICC(2,1 ) = 0.433 ] . Results also revealed no significant effect of tDCS at the group level . Using this common protocol , we found the effects of tDCS on MEP amplitudes to be highly variable at the individual level . In addition , no significant effects of tDCS on MEP amplitude were found at the group level . Future studies should consider utilizing a more strict experimental protocol to potentially account for intra-individual response variations Transcranial direct current stimulation ( tDCS ) is a representative non-invasive brain stimulation method ( NIBS ) . tDCS increases cortical excitability not only in healthy individuals , but also in stroke patients where it contributes to motor function improvement . Recently , two additional types of transcranial electrical stimulation ( tES ) methods have been introduced that may also prove beneficial for stimulating cortical excitability ; these are transcranial r and om noise stimulation ( tRNS ) and transcranial alternating current stimulation ( tACS ) . However , comparison of tDCS with tRNS and tACS , in terms of efficacy in cortical excitability alteration , has not been reported thus far . We compared the efficacy of the three different tES methods for increasing cortical excitability using the same subject population and same current intensity . Fifteen healthy subjects participated in this study . Similar stimulation patterns ( 1.0 mA and 10 min ) were used for the three conditions of stimulation ( tDCS , tRNS , and tACS ) . Cortical excitability was explored via single-pulse TMS elicited motor evoked potentials ( MEPs ) . Compared with pre- measurements , MEPs significantly increased with tDCS , tACS , and tRNS ( p < 0.05 ) . Compared with sham measurements , significant increases in MEPs were also observed with tRNS and tACS ( p < 0.05 ) , but not with tDCS . In addition , a significant correlation of the mean stimulation effect was observed between tRNS and tACS ( p = 0.019 , r = 0.598 ) . tRNS induced a significant increase in MEP compared with the Pre or Sham at all time points . tRNS result ed in the largest significant increase in MEPs . These findings suggest that tRNS is the most effective tES method and should be considered as part of a treatment plan for improving motor function in stroke patients 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 The common aim of transcranial stimulation methods is the induction or alterations of cortical excitability in a controlled way . Significant effects of each individual stimulation method have been published ; however , conclusive direct comparisons of many of these methods are rare . The aim of the present study was to compare the efficacy of three widely applied stimulation methods inducing excitability enhancement in the motor cortex : 1 mA anodal transcranial direct current stimulation ( atDCS ) , intermittent theta burst stimulation ( iTBS ) , and 1 mA transcranial r and om noise stimulation ( tRNS ) within one subject group . The effect of each stimulation condition was quantified by evaluating motor-evoked-potential amplitudes ( MEPs ) in a fixed time sequence after stimulation . The analyses confirmed a significant enhancement of the M1 excitability caused by all three types of active stimulations compared to sham stimulation . There was no significant difference between the types of active stimulations , although the time course of the excitatory effects slightly differed . Among the stimulation methods , tRNS result ed in the strongest and atDCS significantly longest MEP increase compared to sham . Different time courses of the applied stimulation methods suggest different underlying mechanisms of action . Better underst and ing may be useful for better targeting of different transcranial stimulation techniques Previous research ers have approved the ability of anodal transcranial direct current stimulation ( a-tDCS ) of the primary motor cortex ( M1 ) to enhance corticospinal excitability ( CSE ) . The primary aim of the current study was to investigate the effect of concurrent stimulation of M1 and a functionally connected cortical site of M1 on CSE modulation . This new technique is called unihemispheric concurrent dual-site a-tDCS ( a-tDCSUHCDS ) . The secondary aim was to investigate the mechanisms underlying the efficacy of this new approach in healthy individuals . In a r and omized crossover study , 12 healthy right-h and ed volunteers received a-tDCS under five conditions : a-tDCS of M1 , a-tDCSUHCDS of M1-dorsolateral prefrontal cortex ( DLPFC ) , a-tDCSUHCDS of M1- primary sensory cortex ( S1 ) , a-tDCSUHCDS of M1- primary visual cortex ( V1 ) , and sham a-tDCSUHCDS .  Peak-to-peak amplitude of transcranial magnetic stimulation ( TMS ) induced MEPs , short-interval intracortical inhibition ( SICI ) and intracortical facilitation ( ICF ) were assessed before and four times after each condition . A-tDCSUHCDS conditions induced larger MEPs than conventional a-tDCS . The level of M1 CSE was significantly higher following a-tDCSUHCDS of M1-DLPFC than other a-tDCSUHCDS conditions ( p < 0.001 ) , and lasted for over 24 h. The paired-pulse TMS results after a-tDCS of M1-DLPFC showed significant facilitatory increase and inhibitory change . A-tDCSUHCDS of M1-DLPFC increases M1 CSE twofold that of conventional a-tDCS . A-tDCSUHCDS of M1-DLPFC enhances the activity of glutamergic mechanisms for at least 24 h. Such long-lasting M1 CSE enhancement induced by a-tDCSUHCDS of M1-DLPFC could be a valuable finding in clinical scenarios such as learning , motor performance , or pain management . The present study has been registered on the Australian New Zeal and Clinical Trial at http://www.anzctr.org.au/ with registry number of ACTRN12614000817640 Background Transcranial direct current stimulation ( tDCS ) is a non-invasive technique that modulates the excitability of neurons within the primary motor cortex ( M1 ) . Research shows that anodal-tDCS applied over the non-dominant M1 ( i.e. unilateral stimulation ) improves motor function of the non-dominant h and . Similarly , previous studies also show that applying cathodal tDCS over the dominant M1 improves motor function of the non-dominant h and , presumably by reducing interhemispheric inhibition . In the present study , one condition involved anodal-tDCS over the non-dominant M1 ( unilateral stimulation ) whilst a second condition involved applying cathodal-tDCS over the dominant M1 and anodal-tDCS over non-dominant M1 ( bilateral stimulation ) to determine if unilateral or bilateral stimulation differentially modulates motor function of the non-dominant h and . Using a r and omized , cross-over design , 11 right-h and ed participants underwent three stimulation conditions : 1 ) unilateral stimulation , that involved anodal-tDCS applied over the non-dominant M1 , 2 ) bilateral stimulation , whereby anodal-tDCS was applied over the non-dominant M1 , and cathodal-tDCS over the dominant M1 , and 3 ) sham stimulation . Transcranial magnetic stimulation ( TMS ) was performed before , immediately after , 30 and 60 minutes after stimulation to eluci date the neural mechanisms underlying any potential after-effects on motor performance . Motor function was evaluated by the Purdue pegboard test . Results There were significant improvements in motor function following unilateral and bilateral stimulation when compared to sham stimulation at all-time points ( all P < 0.05 ) ; however there was no difference across time points between unilateral and bilateral stimulation . There was also a similar significant increase in corticomotor excitability with both unilateral and bilateral stimulation immediately post , 30 minutes and 60 minutes compared to sham stimulation ( all P < 0.05 ) . Unilateral and bilateral stimulation reduced short-interval intracortical inhibition ( SICI ) immediately post and at 30 minutes ( all P < 0.05 ) , but returned to baseline in both conditions at 60 minutes . There was no difference between unilateral and bilateral stimulation for SICI ( P > 0.05 ) . Furthermore , changes in corticomotor plasticity were not related to changes in motor performance . Conclusion These results indicate that tDCS induced behavioural changes in the non-dominant h and as a consequence of mechanisms associated with use-dependant cortical plasticity that is independent of the electrode arrangement Background Premotor cortical regions ( PMC ) play an important role in the orchestration of motor function , yet their role in compensatory mechanisms in a disturbed motor system is largely unclear . Previous studies are consistent in describing pronounced anatomical and functional connectivity between the PMC and the primary motor cortex ( M1 ) . Lesion studies consistently show compensatory adaptive changes in PMC neural activity following an M1 lesion . Non-invasive brain modification of PMC neural activity has shown compensatory neurophysiological aftereffects in M1 . These studies have contributed to our underst and ing of how M1 responds to changes in PMC neural activity . Yet , the way in which the PMC responds to artificial inhibition of M1 neural activity is unclear . Here we investigate the neurophysiological consequences in the PMC and the behavioral consequences for motor performance of stimulation mediated M1 inhibition by cathodal transcranial direct current stimulation ( tDCS ) . Purpose The primary goal was to determine how electrophysiological measures of PMC excitability change in order to compensate for inhibited M1 neural excitability and attenuated motor performance . Hypothesis Cathodal inhibition of M1 excitability leads to a compensatory increase of ipsilateral PMC excitability . Methods We enrolled 16 healthy participants in this r and omized , double-blind , sham-controlled , crossover design study . All participants underwent navigated transcranial magnetic stimulation ( nTMS )  to identify PMC and M1 corticospinal projections as well as to evaluate electrophysiological measures of cortical , intracortical and interhemispheric excitability . Cortical M1 excitability was inhibited using cathodal tDCS . Finger-tapping speeds were used to examine motor function . Results Cathodal tDCS successfully reduced M1 excitability and motor performance speed . PMC excitability was increased for longer and was the only significant predictor of motor performance . Conclusion The PMC compensates for 
    Output:
    
Using a r and om-effects model , meta- analysis of a-tDCS , c-tDCS , tACS , tRNS and tPCS studies showed statistically non-significant pre-post effects of sham interventions on CSE .
This review found evidence for statically non-significant effects of sham tES on CSE