***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: Abstract Due to the high interindividual response variability following transcranial direct current stimulation ( tDCS ) , it is apparent that further research of the long‐lasting effects of the stimulation technique is required . We aim ed to investigate interindividual variability following anodal tDCS and cathodal tDCS in a large‐scale prospect i ve cross‐over study . Motor cortex physiology measurements were obtained using transcranial magnetic stimulation ( TMS ) in 59 healthy participants comparing motor‐evoked potential ( MEP ) magnitudes following two tDCS paradigms : 1 mA anodal tDCS for 13 min and 1 mA cathodal tDCS for 9 min . Analysis compared MEP changes over time for both polarities . Additionally , we applied hierarchical cluster analysis to assess the dynamics of poststimulation changes . Overall , anodal tDCS result ed in a significant increase in corticospinal excitability lasting for 40 min poststimulation , whereas cathodal tDCS did not alter corticospinal excitability . Cluster analysis revealed for cathodal tDCS both a cluster showing significant stable MEP reduction and a second cluster displaying MEP increase over time . Two diametrical clusters were also found for anodal tDCS . Regardless of polarity , individuals with MEP increase following stimulation showed steeper cortical recruitment curves compared to the clusters with decreased MEP magnitudes . The observed findings confirm a bidirectional modulation of corticospinal excitability following 1 mA tDCS in separate subgroups and the relationship to cortical recruitment Brain-derived neurotrophic factor ( BDNF ) genotype can influence neural response to repetitive transcranial magnetic stimulation ( rTMS ) in normal individuals . In this study we established personalized stimulus intensity of facilitatory rTMS according to BDNF genotype in stroke patients . Twenty-two chronic stroke patients were enrolled . All patients underwent three different sessions of rTMS over the ipsilesional M1 in r and omized order with a washout period exceeding 24h : first condition , high-frequency rTMS with sub-threshold intensity ; second condition , high-frequency rTMS with supra-threshold intensity ; third condition , sham rTMS .  Cortical excitability in the affected hemisphere was assessed with motor evoked potentials ( MEPs ) before and after stimulation . Data were analyzed according to BDNF genotype . Six [ 27.3 % ] and 16 [ 72.7 % ] participants were classified in the Val/Val group and Met allele group , respectively . In each group , significant increases were observed in the amplitude of MEPs after the stimulation in the first and second conditions ( p<0.05 ) , but not in the third condition . However , a significantly higher increase of amplitude of MEPs was observed between the first and second conditions in only the Val/Val group ( p<0.05 ) . BDNF genotype and stimulus intensity should be considered when high-frequency rTMS is used for the modulation of cortical excitability in patients with chronic stroke 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 Negative symptoms are highly relevant in the long-term course of schizophrenia and are an important target domain for the development of novel interventions . Recently , transcranial direct current stimulation ( tDCS ) of the prefrontal cortex has been investigated as a treatment option in schizophrenia . In this proof-of-concept study , 20 schizophrenia patients with predominantly negative symptoms were r and omized to either 10 sessions of add-on active ( 2 mA , 20min ) or sham tDCS ( anode : left DLPFC/F3 ; cathode : right supraorbital/F4 ) . Primary outcome measure was the change in the Scale for the Assessment of Negative Symptoms ( SANS ) sum score ; secondary outcomes included reduction in Positive and Negative Syndrome Scale ( PANSS ) scores and improvement of depressive symptoms , cognitive processing speed , and executive functioning .  Sixteen patients underwent 4 functional connectivity magnetic resonance imaging ( fcMRI ) scans ( pre and post 1st and pre and post 10th tDCS ) to investigate changes in resting state network connectivity after tDCS . Per- protocol analysis showed a significantly greater decrease in SANS score after active ( -36.1 % ) than after sham tDCS ( -0.7 % ) . PANSS sum scores decreased significantly more with active ( -23.4 % ) than with sham stimulation ( -2.2 % ) . Explorative analysis of fcMRI data indicated changes in subgenual cortex and dorsolateral prefrontal cortex ( DLPFC ) connectivity within frontal-thalamic-temporo-parietal networks . The results of this first proof-of-concept study indicate that prefrontal tDCS may be a promising intervention for treatment of schizophrenia with predominant negative symptoms . Large-scale r and omized controlled studies are needed to further establish prefrontal tDCS as novel treatment for negative symptoms in schizophrenia BACKGROUND The brain-derived neurotrophic factor ( BDNF ) gene often shows a single nucleotide polymorphism that is thought to influence synaptic plasticity . It also affects the modulatory effects of repetitive transcranial magnetic stimulation ( rTMS ) on motor cortex excitability . OBJECTIVE This study investigated whether BDNF polymorphism influences the effect of  rTMS  on the motor recovery of patients with stroke . METHODS Forty-four patients ( mean age 53.8 years ) experiencing unilateral motor weakness after stroke were recruited .  rTMS was applied over the primary motor cortex of the affected hemisphere at 10 Hz with 1000 pulses/day for 10 days . Each patient 's motor functions were assessed using the Fugl-Meyer assessment ( FMA ) and the  box and block test ( BBT ) before , immediately after and 2 months after the intervention . BDNF genotyping was performed via PCR assays of whole blood sample s. The patients ' data were grouped and analysed into Val/Val and Met allele groups according to the presence or absence of the BDNF polymorphism . RESULTS Nine patients ( 20.5 % ) were classified into the Val/Val group , and thirty-seven patients ( 79.5 % ) were classified into the Met allele group . The patients ' baseline motor functions did not differ between the two groups . The FMA and BBT scores showed significant improvement immediately after and 2 months after rTMS in both groups . In addition , the time and groups were found to interact significantly , with the Val/Val group improving to a greater extent than the Met allele group in terms of their FMA and BBT scores . CONCLUSIONS The findings suggest that the BDNF gene polymorphism negatively influences the effect of  rTMS  on the motor recovery of upper extremities in stroke patients Dysfunction of the basal ganglia-thalamocortical motor circuit is a fundamental model to account for motor symptoms in Parkinson 's disease ( PD ) . Using high-frequency repetitive transcranial magnetic stimulation ( rTMS ) over the supplementary motor area ( SMA ) , we investigated whether modulation of SMA excitability engenders therapeutic effects on motor symptoms in PD . In this double-blind placebo-controlled study , 99 patients were enrolled and assigned r and omly to SMA-stimulation and sham-stimulation groups . For SMA stimulation , 20 trains of 50 transcranial magnetic stimuli at 5 Hz were delivered at an intensity of 110 % active motor threshold for leg muscles in one session . The sham stimulation was 20 trains of electric stimuli given through electrodes fixed on the head to mimic the cutaneous sensation during rTMS . Each session of intervention was carried out once a week for the first 8 weeks . The SMA stimulation , in contrast to the sham stimulation , engendered significant improvements in total scores and motor scores of the Unified Parkinson 's Disease Rating Scale . Mean improvements in motor scores were 4.5 points in the SMA-stimulation group and -0.1 points in the sham-stimulation group . Results indicate that 5 Hz rTMS over SMA modestly improves motor symptoms in PD patients ; SMA is a potential stimulation site for PD treatment The brain-derived neurotrophic factor gene ( BDNF ) is one of many genes thought to influence synaptic plasticity in the adult brain and shows a common single nucleotide polymorphism ( BDNF Val66Met ) in the normal population that is associated with differences in hippocampal volume and episodic memory . It is also thought to influence possible synaptic changes in motor cortex following a simple motor learning task . Here we extend these studies by using new non-invasive transcranial magnetic stimulation ( TMS ) and transcranial direct current stimulation ( TDCS ) techniques that directly test the excitability and plasticity of neuronal circuits in human motor cortex in subjects at rest . We investigated whether the susceptibility to TMS probes of plasticity is significantly influenced by the BDNF polymorphism . Val66Met carriers were matched with Val66Val individuals and tested on the following protocol s : continuous and intermittent theta burst TMS ; median nerve paired associative stimulation ; and homeostatic plasticity in the TDCS/1 Hz rTMS model . The response of Met allele carriers differed significantly in all protocol s compared with the response of Val66Val individuals . We suggest that this is due to the effect of BNDF on the susceptibility of synapses to undergo LTP/LTD . The circuits tested here are implicated in the pathophysiology of movement disorders such as dystonia and are being assessed as potential new targets in the treatment of stroke . Thus the polymorphism may be one factor that influences the natural response of the brain to injury and disease CONTEXT Consecutive sessions of transcranial direct current stimulation ( tDCS ) over the primary motor cortex ( M1 ) may be a suitable therapy to treat chronic pain , as it can modulate neural activities in the stimulated and interconnected regions . OBJECTIVES The present study investigated the analgesic effect of five consecutive days of anodal/sham tDCS using subjective ( visual analog scale [ VAS ] ) and objective ( cortical excitability measured by transcranial magnetic stimulation [ TMS ] ) measurements . METHODS Patients with therapy-resistant chronic pain syndromes ( trigeminal neuralgia , poststroke pain syndrome , back pain , fibromyalgia ) participated . As this clinical trial was an exploratory study , statistical analyses implemented exploratory methods . Twelve patients , who underwent both anodal and sham tDCS , were analyzed using a crossover design . An additional nine patients had only anodal or sham stimulation . tDCS was applied over the h and area of the M1 for 20 minutes , at 1mA for five consecutive days , using a r and omized , double-blind design . Pain was assessed daily using a VAS rating for one month before , during , and one month post-stimulation . M1 excitability was determined using paired-pulse TMS . RESULTS Anodal tDCS led to a greater improvement in VAS ratings than sham tDCS , evident even three to four weeks post-treatment . Decreased intracortical inhibition was demonstrated after anodal stimulation , indicating changes in cortico-cortical excitability . No patient experienced severe adverse effects ; seven patients suffered from light headache after anodal and six after sham stimulation . CONCLUSION Results confirm that five daily sessions of tDCS over the h and area of the M1 can produce long-lasting pain relief in patients with chronic pain OBJECTIVE To investigate whether there is a relation between the plasticity induced by different intensities of facilitatory rTMS with different intensities and brain-derived neurotrophic factor ( BDNF ) genotype . METHODS Forty healthy volunteers ( 14 men , mean age 27.3years ) were enrolled . All participants received three high-frequency rTMS applications in r and om order over the non-dominant primary motor cortex with more than a 24-h washout period : 1st condition , rTMS with sub-threshold intensity ; 2nd condition , rTMS with supra-threshold intensity ; and 3rd condition , sham rTMS .  Cortical excitability was assessed before and after rTMS using motor-evoked potentials ( MEPs ) . Data were analyzed using the BDNF genotype . RESULTS Twelve , 19 , and 9 participants were classified into Val/Val , Val/Met , and Met/Met groups , respectively . In each group , there were significant increases in the amplitude of MEPs after 1st and 2nd conditions ( P<0.05 ) , but not after 3rd condition . In Val/Val group , the increase ratio of MEPs ' amplitude after 2nd condition was significantly higher than 1st condition ( P<0.05 ) 
    Output:
    
The results indicate that variation in brain-derived neurotrophic factor genotypes may have an effect on CSE after NIBS .
Variation between younger and older adults also affects CSE after NIBS .
Variation between age-matched males and females does not affect CSE after NIBS , but variation across the menstrual cycle does .
Variation between skull thickness and brain tissue morphology influences the electric field magnitude that ultimately reaches the primary motor cortex .
These findings indicate that biological and anatomical variations may in part account for interindividual variability in CSE in response to NIBS of the primary motor cortex , categorizing individuals as responding as expected ( responders ) or not responding as expected ( nonresponders )