***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: OBJECTIVE To determine whether a single session of anodal transcranial direct current stimulation to the left dorsolateral prefrontal cortex improves attention in patients with traumatic brain injury . DESIGN Double-blinded , cross-over design . PATIENTS Nine patients with attention deficit after traumatic brain injury . METHODS Patients underwent a computerized contrast reaction time task before and after the administration of real transcranial direct current stimulation ( 2 mA for 20 min ) or sham transcranial direct current stimulation ( 2 mA for 1 min ) to the left dorsolateral prefrontal cortex in a double-blind , crossover manner . RESULTS Immediately post-stimulation , the transcranial direct current stimulation group showed a tendency of shortened reaction time relative to baseline ( 87.3 ± 7.8 % ) , whereas the sham stimulation group ( 122.4 ± 715.5 % ) did not ( p = 0.056 ) . However , this difference was not significant 3 or 24 h after stimulation ( p > 0.05 ) . The numbers of correct responses were not changed at any time after stimulation . CONCLUSION Anodal transcranial direct current stimulation applied to the left dorsolateral prefrontal cortex improves attention compared with sham stimulation in patients with traumatic brain injury , which suggests a potential role for this intervention in improving attention during cognitive training after traumatic brain injury . A further prospect i ve r and omized trial is required to confirm the benefits conferred by transcranial direct current stimulation in this patient population The present study investigated emotional memory following bilateral transcranial electrical stimulation ( direct current of 1 mA , for 20 minutes ) over fronto-temporal cortical areas of healthy participants during the encoding of images that differed in affective arousal and valence . The main result was a significant interaction between the side of anodal stimulation and image emotional valence . Specifically , right anodal/left cathodal stimulation selectively facilitated the recall of pleasant images with respect to both unpleasant and neutral images whereas left anodal/right cathodal stimulation selectively facilitated the recall of unpleasant images with respect to both pleasant and neutral images . From a theoretical perspective , this double dissociation between the side of anodal stimulation and the advantage in the memory performance for a specific type of stimulus depending on its pleasantness supported the specific-valence hypothesis of emotional processes , which assumes a specialization of the right hemisphere in processing unpleasant stimuli and a specialization of the left hemisphere in processing pleasant stimuli . From a method ological point of view , first we found tDCS effects strictly dependent on the stimulus category , and second a pattern of results in line with an interfering and inhibitory account of anodal stimulation on memory performance . These findings need to be carefully considered in applied context s , such as the rehabilitation of altered emotional processing or eye-witness memory , and deserve to be further investigated in order to underst and their underlying mechanisms of action Cognitive control ( CC ) over emotional distraction  is of particular importance for adaptive human behaviour and is associated with activity in the left dorsolateral prefrontal cortex ( dlPFC ) . Deficient CC , e.g. , presenting as negativity bias , has been suggested to underlie many of the core symptoms of major depression ( MD ) and is associated with impairments of dlPFC function . Correspondingly , enhancement of dlPFC activity with anodal transcranial direct current stimulation ( tDCS ) can ameliorate these impairments in patients with MD . Here , we tested the hypothesis that a reduction of dlPFC activity by cathodal tDCS induces CC deficits , thus triggering a depression-like negativity bias in healthy subjects . Twenty-eight individuals participated in a double-blinded , balanced r and omized crossover trial of cathodal ( 1 mA , 20 min ) and sham tDCS applied to the left dlPFC . To assess CC we conducted a delayed response working memory ( DWM ) task and an arithmetic inhibition task ( AIT ) with pictures of varying valent content ( negative , neutral , positive ) during and immediately after stimulation . Cathodal tDCS led to impaired CC specifically over negative material as assessed by reduced response accuracy in the DWM and prolonged response latency in the AIT . Hence , the current study supports the notion that left dlPFC is critically involved in CC over negative material . Together with previously reported beneficial anodal effects , it indicates that the hypoactivation of left dlPFC causes deficits in CC over negative material , which is a possible aetiological mechanism of depression In this study , we explored the representation of an incongruent action ( instrumentally incorrect use of an object ) in comparison with sentences ending with an incongruent action word , taking into account the role of the activation of the left dorsolateral pFC ( DLPFC ) . This activity was appositely modulated by transcranial direct current stimulation ( tDCS ) . The effect of tDCS when participants processed congruent/incongruent object-related actions ( Experiment 1 ) or sentences ( Experiment 2 ) was verified by measuring changes in the ERP N400 , error rates ( ERs ) , and RTs . In Experiment 1 , 30 participants performed the detection task  within a dynamic  context ( video tapes representing a sequence of four action frames ) . In Experiment 2 , 28 participants read sentences that represented object-related actions . The stimulation effect ( a cathode applied to the DLPFC and an anode to the right supraorbital region ) was analyzed by comparing the ER , RT , and ERP profiles before and after stimulation ( or sham treatment ) . A significant reduction of the N400 was observed for incongruent stimuli in the case of cathodal ( inhibitory ) stimulation of the DLPFC in comparison with prestimulation conditions for Experiment 1 , but not Experiment 2 . Moreover , ERs were increased , and RTs were reduced in response to incongruent conditions after tDCS , but not after sham stimulation in Experiment 1 . It is suggested that perturbation of the DLPFC may limit the ability to analyze a semantically anomalous action sequence as a reduced N400 ERP effect and increased r and om responses was observed . Finally , the contribution of the frontal area to the semantic processing of actions is discussed BACKGROUND Transcranial direct current stimulation ( tDCS ) is increasingly discussed as a new option to support the cognitive rehabilitation in neuropsychiatric disorders . However , the therapeutic impact of tDCS is limited by high inter-individual variability . Genetic factors most likely contribute to this variability by modulating the effects of tDCS . OBJECTIVES We aim ed to investigate the influence of the COMT Val(108/158)Met polymorphism on cathodal tDCS effects on executive functioning . METHODS Cathodal tDCS was applied to the left dorsolateral prefrontal cortex ( dlPFC ) during the performance of a parametric Go/No-Go test . RESULTS We demonstrate an impairing effect of cathodal tDCS to the dlPFC on response inhibition . This effect was only found in individuals homozygous for the Val-allele of the COMT Val(108/158)Met polymorphism . No effects of stimulation on executive functions in Met-allele carriers were detected . CONCLUSION Our data indicate that i ) cathodal , excitability reducing tDCS , interferes with inhibitory cognitive control , ii ) the left dlPFC is critically involved in the neuronal network underlying the control of response inhibition , and iii ) the COMT Val(108/158)Met polymorphism modulates the impact of cathodal tDCS on inhibitory control . Together with our previous finding that anodal tDCS selectively impairs set-shifting abilities in COMT Met/Met homozygous individuals , these results indicate that genetic factors modulate effects of tDCS on cognitive performance . Therefore , future tDCS research should account for genetic variability in the design and analysis of neurocognitive as well as therapeutic applications to reduce the variability of results and facilitate individualized neurostimulation approaches 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 Background : Word retrieval during verbal fluency tasks invokes both automatic and controlled cognitive processes . A distinction has been made between the generation of words clusters and switches between such clusters on verbal fluency tasks . Clusters , defined by the reporting of contiguous words that constitute semantic or phonemic subcategories , are thought to reflect relatively automatic processing . In contrast , switching from one subcategory to another is thought to require a more controlled , effortful form of cognitive processing . Objective : In this single-blind , sham-controlled experiment , we investigated whether anodal and cathodal transcranial direct current stimulation ( tDCS ) can differentially modify controlled or automatic processes that support lexical retrieval , as assessed by clustering and switching on verbal fluency tasks , in 24 healthy right-h and ed adults . Methods : Participants were r and omly assigned to receive 1 mA of either anodal ( excitatory ) or cathodal ( inhibitory ) active tDCS over the left dorsolateral prefrontal cortex in addition to sham stimulation over the same region in counterbalanced order . Participants engaged in various cognitive activities during the first 23 min of stimulation . Then , during the final segment of each 30-min session , they completed letter- and category-cued word fluency tasks . Results : Participants reported more words on category-cued word fluency tasks during anodal than sham stimulation ( 25.9 vs. 23.0 words ; p = 0.055 ) . They also showed a net increase in the number of clustered words during anodal stimulation compared to a net decrease during cathodal stimulation ( 1.3 vs. −1.5 words ; p = 0.038 ) . Conclusion : tDCS can selectively alter automatic aspects of speeded lexical retrieval in a polarity-dependent fashion during a category-guided fluency task PURPOSE Attention decline after stroke is common and hampers the rehabilitation process , and non-invasive transcranial direct current stimulation ( tDCS ) has the potential to elicit behavioral changes by modulating cortical excitability . The authors tested the hypothesis that a single session of non-invasive cortical stimulation with excitatory anodal tDCS applied to the left dorsolateral prefrontal cortex ( DLPFC ) can improve attention in stroke patients . METHODS Ten patients with post-stroke cognitive decline ( MMSE 25 ) and 10 age-matched healthy controls participated in this double blind , sham-controlled , crossover study involving the administration of real ( 2 mA for 20 min ) or sham stimulation ( 2 mA for 1 min ) to the left DLPFC . Attention was measured using a computerized Go/No-Go test before and after intervention . Improvements in accuracy and speed after stimulation relative to baseline were compared for real and sham stimulations . RESULTS In healthy controls , no significant improvement in Go/No-Go test was observed after either real or sham stimulation . However , in stroke patients , tDCS led to a significant improvement in response accuracy at 1 hour post-stimulation relative to baseline , and this improvement was maintained until 3 hours post-stimulation ( P < 0.05 ) , whereas sham stimulation did not lead to a significant improvement in response accuracy ( P > 0.05 ) . Changes in reaction times were comparable for the two stimulations ( P > 0.05 ) . CONCLUSION Non invasive anodal tDCS applied to the left DLPFC was found to improve attention versus sham stimulation in stroke patients , which suggests that non-invasive cortical intervention could potentially be used during rehabilitative training to improve attention Introduction Working memory plays a critical role in cognitive processes which are central to our daily life . Neuroimaging studies have shown that one of the most important areas corresponding to the working memory is the dorsolateral prefrontal cortex ( DLFPC ) . This study was aim ed to assess whether bilateral modulation of the DLPFC using a noninvasive brain stimulation , namely transcranial direct current stimulation ( tDCS ) , modifies the working memory function in healthy adults . Methods In a r and omized sham-controlled cross-over study , 60 subjects ( 30 Males ) received sham and active tDCS in two subgroups ( anode left/cathode right and anode right/cathode left ) of the DLPFC . Subjects were presented working memory n-back task while the reaction time and accuracy were recorded . Results A repeated measures , mixed design ANOVA indicated a significant difference between the type of stimulation ( sham vs. active ) in anodal stimulation of the left DLPFC with cathodal stimulation of the right DLPFC [ F(1,55)= 5.29 , P=0.019 ] , but not the inverse polarity worsened accuracy in the 2-back working memory task . There were also no statistically significant changes in speed of working memory [ F(1,55)= 0.458,P=0.502 ] related to type or order of stimulation . Discussion The results would imply to a polarity dependence of bilateral tDCS of working memory . Left anodal/ right cathodal stimulation of DLP 
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Importantly , different stimulation parameters affected a-tDCS effects , but not c-tDCS effects , on accuracy in healthy sample s vs. PATIENTS increased current density and density charge result ed in improved accuracy in healthy sample s , most prominently in females ; for neuropsychiatric patients , task performance during a-tDCS result ed in stronger increases in accuracy rates compared to task performance following a-tDCS .
CONCLUSIONS Healthy participants  respond faster , but not more accurate on cognitive tasks after a-tDCS .
However , increasing the current density and /or charge might be able to enhance response accuracy , particularly in females .
In contrast , online task performance leads to greater increases in response accuracy than offline task performance in neuropsychiatric patients .