transcranial direct current stimulation ( tdcs ) can be utilized as a key tool because it can 
 affect the neural plasticity of the cerebral cortex .
furthermore , it can directly change the 
 excitability of electrical potentials in a stimulated region , as well as indirectly affect 
 the excitability of the same region at the other side of the cerebrum1 .
such tdcs can also cause polarity - dependent changes in the 
 excitability of the cerebral motor cortex2 .
negative - polarity stimulation , on the other hand , decreases 
 excitability due to hyperpolarization occurring at the neurons or neural networks in 
 corresponding regions .
the study conducted by fregni et al.4 
 revealed that tdcs improved working memory performance in a consecutive sequential 
 letter - matching test , while antal et al.5 
 showed in their study that tdcs influenced visual cognitive function in the contrast 
 sensitivity test , a visual function test tdcs - related studies have mostly used carbon rubber 
 electrodes in applications involving scalp electrodes .
carbon rubber electrodes are very 
 inconvenient to use and are disliked by subjects because the face must be wrapped using 
 separate straps , to keep the electrodes in place .
therefore , this study was conducted to 
 investigate the effects of electrode type on n100 and p300 when tdcs was applied to a 
 primary motor area .
this study selected 30 healthy adult females in their 20 s who had a non - dominant left 
 hand .
we obtained approval for this experiment from the research ethics committee of kwangju 
 women s university .
group i were administered tdcs with carbon rubber electrodes , while round , 
 self - adhesive electrodes were used for group ii .
the general features of the subjects are 
 presented in table 1table 1.general characteristics of the subjectsgroup i ( n=10)group ii ( n=10)age ( years)20.60.521.51.1height ( cm)161.33.7162.11.5weight ( kg)55.18.656.67.1meansd .
group ii : a circular adhesive 
 electrode tdcs was applied using an endomed 482 ( enraf - nonius b.v . ,
, the positive electrode was 
 placed over the primary motor cortex at c4 , and the negative electrode was placed at c3 .
the 
 pulse duration was set to 2  ms , and the interpulse duration to 5  ms .
carbon rubber electrodes 4  6  cm ( daeyang medical , wonju , south korea ) were 
 used for experimental group i with a current intensity of 0.058 ma / cm , and 
 1.77  cm round , self - adhesive electrodes ( skintact , leonhard lang gmbh , 
 innsbruck , australia ) were used for experimental group ii with a current intensity of 0.06 
 ma / cm . to measure event - related brain potentials ( erp ) , an eeg-8 electroencephalograph ( lxe5208 , 
 laxtha , daejeon , south korea ) was used , and the telescan software ( laxtha , daejeon , south 
 korea ) program was used to conduct the latency and amplitude analyses of n100 and p300 .
the 
 sampling rate was set to 256  hz , and band - pass filtered between 1~50  hz .
the attachment 
 regions were wiped clean with alcohol to reduce regional resistance to less than 5 k before 
 the electrodes were attached .
the ag - agcl electrodes were attached to the fp1 and fp2 areas ; 
 the active electrode was placed on the right mastoid , and the earth electrode was placed on 
 the left mastoid , in accordance with the international 1020 system placement method .
the erp , which is the average of brainwaves , appears after stimulating the targets , was 
 analyzed based on the maximum negative potential value observed between 80 and 120  ms for 
 n100 and on the maximum positive potential value between 250 and 500  ms for p300 .
the subjects were requested to move a blue - colored arrows in the arrow 
 direction by their non - dominant left hand , and the red - colored arrows in the direction away 
 from the arrow .
visual stimulation was presented a total of 50 times , among which 18 times 
 were designated for target stimulation ( red arrow ) and 32 times for non - target stimulation 
 ( blue arrow ) . the temporal interval between each stimulation
was set at 1 second , and each 
 time duration was randomly presented between 2 to 4 seconds .
repeated measures anova was used to analyze the 
 changes in the two groups according to the duration of treatment .
the results of the experiment show that the n100 latency and amplitude had statistically 
 insignificant differences in the interactions between time and group in both the fp1 and fp2 
 areas .
however , a statistically significant difference was found in the main effect duration 
 ( p<0.05 ) in both areas ( table 2table 2.changes in n100eeggrouplatency ( sec)amplitude ( v)prepostprepostfp1i0.140.040.130.046.376.917.287.58ii0.130.030.110.047.589.408.509.88fp2i0.140.040.130.036.717.237.917.07ii0.140.030.120.037.499.138.958.16mean  sd . at fp1 and fp2 , there were only significant changes depending on time in 
 the latency ( p<0.05 ) and amplitude ( p<0.05 ) , but there was no statistically 
 significant difference in interaction effect .
thus , tdcs application reduced the n100 latency and increased its amplitude , 
 regardless of the type of electrode .
the p300 latency and amplitude had statistically 
 insignificant differences in interactions between time and group in both the fp1 and fp2 
 areas .
however , a statistically significant difference was found in main effect duration 
 ( p<0.05 ) in both areas ( table 3table 3.changes in p300eeggrouplatency ( sec)amplitude ( v)prepostprepostfp1i0.340.060.320.0512.358.7013.5110.45ii0.330.080.320.0913.8715.0414.2714.97fp2i0.340.040.310.0413.5110.4517.5214.05ii0.330.090.310.1015.2715.1118.0518.29mean  sd . at fp1 and fp2 , there were only significant changes depending on time in 
 the latency ( p<0.05 ) and amplitude ( p<0.05 ) , but there was no statistically 
 significant difference in interaction effect .
thus , tdcs application reduced the p300 latency and increased its amplitude , 
 regardless of the electrode type .
mean  sd . at fp1 and fp2 , there were only significant changes depending on time in 
 the latency ( p<0.05 ) and amplitude ( p<0.05 ) , but there was no statistically 
 significant difference in interaction effect .
mean  sd . at fp1 and fp2 , there were only significant changes depending on time in 
 the latency ( p<0.05 ) and amplitude ( p<0.05 ) , but there was no statistically 
 significant difference in interaction effect .
utz et al.6 reported that generalized 
 electrode sizes had yet to be established for tdcs ; however , some researchers have 
 recommended using small electrodes to effectively transmit current .
our present results 
 demonstrate that tdcs shortens the latencies and increases the amplitudes of n100 and p300 
 at both the fp1 and fp2 areas , regardless of the electrode type .
n100 reflects early 
 attentiveness in a cerebral process7 ; 
 therefore , it considered to be an indicator of selective attentiveness8 .
in addition , n100 latency represents the complexity and 
 efficiency of synapses involved in information processing speed and responses9 .
therefore , we consider tdcs affected n100 
 latency and amplitude and to have aided the neurophysiologic processes that are related to 
 attentiveness , information processing speed , and the responses of the subjects to external 
 stimuli .
hwang and lee10 reported that tdcs 
 delivered by carbon rubber electrodes to stroke patients primary motor cortex resulted in 
 shorter p300 latency at both the fp1 and 2 areas .
their result is similar to the result our 
 present study , which used healthy people as subjects .
the p300 amplitude represents the 
 amount of cognitive activity , such as memory and attentiveness , and is related to the time 
 it takes to evaluate and classify latencies in response to stimulation11 .
in addition , p300 also represents the 
 information - gathering process of perceptual decisions that identify and determine 
 stimulation from outside influences12 , 13 .
therefore , given that both n100 and p300 
 latencies were shortened , and that their amplitudes increased , regardless of the electrode 
 type , we consider tdcs increased cognitive activities that execute tasks in response to 
 target and non - target stimulation , regardless of the electrode type . consequently ,
since 
 tdcs positively influenced cognitive activities , regardless of the electrode type , we 
 consider self - adhesive electrodes are a better treatment choice because of their 
 user - friendliness and convenience in clinical applications of tdcs compared with carbon 
 rubber electrodes .
 [ purpose ] this study investigated the effects of types of electrode on n100 and p300 in 
 transcranial direct current stimulation ( tdcs ) applications . [ subjects and methods ] thirty 
 subjects were randomly assigned to two groups with 15 subjects in each group depending on 
 the electrode types . 
 a positive electrode on the primary motor area ( c4 ) and a negative 
 electrode on the left primary motor area ( c3 ) , and stimulation was applied for 20 minutes . 
 before and after tdcs , n100 and p300 were measured by attaching an electrode to fp1 and 
 fp2 . [ results ] in tdcs applications , n100 and p300 showed no significant interaction 
 effects between time and group for either latency or amplitude in the fp1 and fp 2 areas , 
 but there was a statistically significant difference in the main effect duration . 
 
 [ conclusion ] the latencies of n100 and p300 were shortened and that their amplitudes 
 increased in both the fp1 and fp2 areas , regardless of the type of electrode . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION