galvanic vestibular stimulation ( gvs ) can be applied to induce the feeling of directional 
 virtual head motion by stimulating the vestibular organs electrically1 .
the mechanisms underlying this response are not yet 
 understood , although the response is commonly attributed to altered otolith output , and 
 based on animal studies , it seems reasonable to assume that vestibular afferents from the 
 otoliths and semicircular canals are similarly affected by gvs2 .
when such a stimulation transmits a signal from the anode and 
 cathode to the vestibular system , postural sway towards the anode occurs3 .
event - related potentials ( erps ) are voltage fluctuations that are associated in time with 
 some physical or mental occurrence4 .
erps 
 are ideal candidates for such end due to their sensitivity to cognitive processes and their 
 high temporal resolution .
abundant research has documented these old / new differences in 
 erps , but the effects of the decision criteria ( or the resulting response bias ) on the erps 
 recorded during the execution of recognition memory tasks have rarely been investigated5 .
lee et al.6 reported , however , that the latencies of n100 and p300 were 
 shortened and that their amplitudes increased in both the fp1 and fp2 areas after 
 transcranial direct current stimulation ( tdcs ) applications .
the p300 wave occurs only if 
 the subject is actively engaged in the task of detecting the targets7 .
attention may also interact with an earlier , apparently 
 exogenous , negative waveform , n18 .
it was reported recently that gvs had a positive influence on improving short - term 
 memory9 , 10 and movement - related cortical potential11 , but studies on the effects of erps related to the 
 cognitive function after gvs application have rarely been reported .
the present study was 
 conducted to examine the effects of gvs on erps in relation to a cognitive function .
the subjects of this study were 40 normal females in their 20s who had the general 
 characteristics listed in table 1table 1.general characteristics of the subjectsgvs group ( n=20)sham group ( n=20)age ( yrs)20.6  0.820.8  0.9height ( cm)162.8  5.0160.9  5.6weight ( kg)57.4  8.154.0  7.1 . approval for this experiment was obtained from the research ethics committee 
 of kwangju women s university .
the subjects were randomly divided into two groups , each 
 consisting of 20 women ( the gvs and sham groups ) .
the 
 participants were asked to assume a comfortable sitting position and to close their eyes . 
 before attaching a disposable adhesive electrodes ( hrtc32 , hurev , south korea ) ,
the 
 attachment areas were washed with an alcohol swab ; electrodes were attached in both mastoid 
 processes .
the anode was applied to the right mastoid process , and the cathode was applied 
 to the left the left .
the pulse duration was 300  ms , and the interpulse duration was 700  ms 
 ( triangular waveform ) .
the intensity was set at 90% of the patient s sensory threshold , and 
 gvs was applied was 10 minutes .
after attaching the electrodes onto the same areas as in the gvs 
 group , the subjects in the sham group were ordered to assume a comfortable sitting position 
 and to close their eyes .
the equipment to examine used erps was an lxe5208 electroencephalograph ( eeg ; laxtha , 
 daejeon , south korea ) .
the study participants were told not to move or talk except while 
 carrying out the visual stimulation tasks , which were carried out by the study participants 
 in a comfortable sitting position . before the measurement of the erps , the electrode 
 attachment areas were washed with alcohol swabs to eliminate debris so that the impedance of 
 the scalp would be under 5 . in the attachment areas for the eeg , an ag / agci electrode was 
 attached to the fp1 , fp2 , fz , cz , p3 , p4 , pz , and oz areas using the international 1020 
 system , the ground electrode was applied to the left mastoid process , and the reference 
 electrode was applied to the right mastoid process .
the sampling rate was set to 256  hz , and 
 eeg signals were low - pass - filtered to 50  hz . the task used for the experiment involved being 
 presented with 40 target stimulations ( matching images of words and pictures , such as the 
 word smell and a picture of a rose ) and 160 nontarget stimulations ( non - matching images of 
 words and pictures , such as the word sit and a picture of a saxophone ) using an oddball 
 paradigm , with a total of 200 target stimulations and the target stimulations being randomly 
 given for 2 sec . n100 and
p300 components of the erps were analyzed using telescan 2.95 
 ( laxtha , daejeon , south korea ) .
n100 are defined as the largest negative - going peaks within a 
 specific latency window : 100150  ms .
p300 are defined as the largest positive - going peaks 
 within a specific latency window : 300500  ms .
data analysis was conducted using spss version 
 17.0 . repeated - measures anova was conducted to determine the differences between the time 
 changes in each group with regard to the measured items .
the n100 latency showed significant differences in interaction effects between time and 
 group only in the f3 ( f1,40=7.992 ; p=0.007 ) , f4 ( f1,40=4.581 ; 
 p=0.039 ) , fz ( f1,40=5.535 ; p=0.024 ) , and pz ( f1,40=7.641 ; p=0.009 ) 
 areas ( table 2table 2.changes in erp latency ( unit :  ms)areagroupn100p300prepostprepostfp1gvs119.5  13.3124.2  21.5340.0  37.6301.8  40.5sham122.9  13.5123.0  14.2324.4  39.2343.4  41.9fp2gvs117.4  14.5120.1  18.4337.9  40.7312.7  36.5sham170.9  13.6154.6  17.6322.5  27.7327.5  44.2f3gvs127.7  14.6117.3  12.8345.6  40.0332.1  45.0sham123.6  15.1122.8  17.9325.0  29.1324.0  33.3f4gvs121.9  13.2118.6  12.5327.7  37.5321.8  41.7sham122.9  12.9122.9  12.0336.5  40.0319.0  43.7fzgvs123.8  12.5116.9  12.9340.0  33.8306.3  29.8sham121.1  15.3123.7  15.3322.5  43.8314.3  43.7czgvs123.6  16.3130.0  19.2337.2  39.6323.8  32.8sham124.7  15.7123.1  15.0317.2  39.1324.5  40.2pzgvs144.3  39.7125.4  15.2337.7  38.4312.3  34.8sham125.6  17.9133.2  14.1336.7  35.2321.3  43.1ozgvs139.6  43.9127.8  16.4327.3  32.4305.3  30.5sham139.5  22.4137.2  30.0307.8  35.1308.2  37.5mean  sd .
the n100 latency showed significant differences in interaction effects 
 between time and group only in the f3 ( f1,40=7.992 ; p=0.007 ) , f4 
 ( f1,40=4.581 ; p=0.039 ) , fz ( f1,40=5.535 ; p=0.024 ) , and pz 
 ( f1,40=7.641 ; p=0.009 ) areas , and the p300 latency showed significant 
 differences in interaction effects between time and group only in the fp1 
 ( f1,40=21.446 ; p=0.000 ) and fp2 ( f1,40=5.251 ; p=0.028 ) 
 areas . ) , while the p300 latency showed significant differences in interaction effects 
 between time and group only in the fp1 ( f1,40=21.446 ; p=0.000 ) and fp2 
 ( f1,40=5.251 ; p=0.028 ) areas .
the n100 latency showed significant differences in interaction effects 
 between time and group only in the f3 ( f1,40=7.992 ; p=0.007 ) , f4 
 ( f1,40=4.581 ; p=0.039 ) , fz ( f1,40=5.535 ; p=0.024 ) , and pz 
 ( f1,40=7.641 ; p=0.009 ) areas , and the p300 latency showed significant 
 differences in interaction effects between time and group only in the fp1 
 ( f1,40=21.446 ; p=0.000 ) and fp2 ( f1,40=5.251 ; p=0.028 ) 
 areas .
the n100 amplitude showed significant differences in interaction effects between time and 
 group only in the fp2 ( f1,40=6.972 ; p=0.012 ) , fz ( f1,40=10.854 ; 
 p=0.002 ) , and pz ( f1,40=9.798 ; p=0.003 ) areas ( table 3table 3.changes in erp amplitude ( unit : v)areagroupn100p300prepostprepostfp1gvs2.29  1.221.70  0.692.30  0.822.70  1.11sham2.04  1.221.52  0.782.33  0.962.19  0.83fp2gvs1.94  1.031.38  0.632.19  1.042.67  1.07sham1.57  1.131.78  1.541.66  0.751.90  0.72f3gvs1.60  0.621.17  0.601.73  0.851.96  0.76sham1.48  1.531.22  0.681.44  0.731.72  0.67f4gvs1.37  0.640.90  0.471.67  0.551.88  0.78sham1.48  1.441.43  1.101.33  0.611.41  0.58fzgvs1.38  0.570.91  0.391.32  0.491.69  0.75sham1.34  1.101.60  1.111.17  0.511.38  0.48czgvs1.27  0.530.97  0.381.23  0.431.52  0.73sham1.32  1.541.10  0.871.12  0.461.22  0.57pzgvs1.45  0.631.09  0.631.30  0.891.79  0.73sham1.93  1.922.63  1.981.35  0.421.40  0.48ozgvs1.51  0.471.14  0.631.36  0.371.69  0.53sham1.55  0.801.18  0.781.35  0.491.41  0.51mean  sd .
the n100 amplitude showed significant differences in interaction effects 
 between time and group only in the fp2 ( f1,40=6.972 ; p=0.012 ) , fz 
 ( f1,40=10.854 ; p=0.002 ) , and pz ( f1,40=9.798 ; p=0.003 ) areas , 
 and the p300 amplitude showed significant differences in interaction effects between 
 time and group only in the fp1 ( f1,40=6.775 ; p=0.013 ) and pz 
 ( f1,40=8.324 ; p=0.006 ) areas . ) , while the p300 amplitude showed significant differences in interaction 
 effects between time and group only in the fp1 ( f1,40=6.775 ; p=0.013 ) and pz 
 ( f1,40=8.324 ; p=0.006 ) areas .
the n100 amplitude showed significant differences in interaction effects 
 between time and group only in the fp2 ( f1,40=6.972 ; p=0.012 ) , fz 
 ( f1,40=10.854 ; p=0.002 ) , and pz ( f1,40=9.798 ; p=0.003 ) areas , 
 and the p300 amplitude showed significant differences in interaction effects between 
 time and group only in the fp1 ( f1,40=6.775 ; p=0.013 ) and pz 
 ( f1,40=8.324 ; p=0.006 ) areas .
the n100 amplitude increased in the fp2 , fz , and pz areas after gvs stimulation , and the 
 n100 latency was faster in the f3 , f4 , fz , and pz areas .
the n100 component of the erp was 
 recorded at the occipital , parietal , central , and frontal lobes12 .
the n100 amplitude increased in the reaction time task 
 and the rapid response of reaction13 and 
 also affected the optional attention in task performance14 .
park15 reported 
 that the n100 latency decreased and that its amplitude increased in the fz , pz , p4 , and oz 
 areas after gvs application .
therefore , it was found in this study that the n100 latency 
 decreased and that its amplitude increased in the fz and pz areas , as in the preceding 
 studies , and that this was because gvs improved the optional attention in the task 
 performance and helped improve the decision - making ability in matching .
the p300 latency was faster in the fp1 and fp2 areas after gvs application , and the p300 
 amplitude increased in the fp1 and pz areas .
the p300 components were found to play a 
 significant role in identifying the depth of cognitive information processing , and the p300 
 amplitude tended to increase immediately after an experimental task , whereas the latency 
 decreased at that time16 .
p300 
 alterations obviously reflect only minor cognitive changes during normal aging17 , but park15 reported that p300 had a shorter latency and a larger amplitude 
 after gvs application in normal adults .
park15 suggested that gvs may affect the cognitive decision for judging 
 the reaction to a target stimulation after receiving the stimulation .
the prefrontal 
 association cortex functions include goal - oriented behavior and self - awareness , and the 
 parietotemporal association cortex functions include sensory integration , problem solving , 
 understanding language , and comprehension of spatial relationships18 .
this study has limitations related to its use of only 
 women in their 20s with normal cognitive function . in this study ,
n100 activation was found in the prefrontal , frontal , and parietal areas of 
 the cerebral cortex after gvs application , whereas p300 activation was mainly found in the 
 prefrontal and parietal areas of the cerebral cortex after gvs application .
these results 
 suggest that gvs may play a positive role in the n100 and p300 components of the erps of the 
 cerebral cortex related to decision - making in matching words with images .
 [ purpose ] the purpose of this study was to examine the effects of galvanic vestibular 
 stimulation on event - related potentials . 
 [ subjects and methods ] forty normal female adult 
 subjects were randomly distributed to a galvanic vestibular stimulation application group 
 ( 20 subjects ) and sham group ( 20 subjects ) . for galvanic vestibular stimulation 
 application , 
 a positive electrode was applied to the right mastoid process , and a negative 
 electrode was applied to the left mastoid process ; simulation was applied for 10 minutes . 
 
 a test was conducted on the n100 and p300 components of the event - related potentials 
 before and after galvanic vestibular stimulation . 
 [ results ] the n100 latency showed 
 statistically significant differences in interaction effects between time and group in the 
 f3 , f4 , fz , and pz areas . 
 the p300 latency showed the same results in the fp1 and fp2 
 areas , the n100 amplitude showed the same results in the fp2 , fz , and pz areas ; and the 
 p300 amplitude showed the same results in the pz area . 
 [ conclusion ] these results suggest 
 that galvanic vestibular stimulation may play a positive role in the n100 and p300 
 components of the event - related potentials of the cerebral cortex related to 
 decision - making in matching words with images . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION