Characteristic of AEP and SEP for Localization of Evoked Potential by Recalling

Abstract

After it keeps hearing a periodic auditory stimulus, it might be able to be recalled like actual sound even if there is no stimulus. To clarify brain activity at this time, EEG source localization was performed. However, in recalling auditory stimulus experiment, when EEG is ensemble averaged, evoked potential may decrease because subject oneself try to recall auditory stimulus according to same timing as periodic stimulus interval. If SEP can be used as a trigger to recall acoustic stimulus, ensemble average is expected to be applied to attract EP (evoked potential) by recalling. But, because somatosensory evoked potential (SEP) occurs by electric stimulation, it is necessary for SEP and auditory evoked potential (AEP) to be the summation characteristics in order to analyze the simultaneous evoked potential (here, it is defined as S-AEP) of an electric stimulus and auditory stimulus. However, unexpectedly such a summation characteristics is not shown in a past study. Therefore, it makes comparative study of AEP and EEG which is reduced SEP from S-AEP. First of all, the correlation coefficient of each scalp electrode was examined about AEP and EEG which is reduced SEP from S-AEP. At this time, 1200 ensemble average was done at each stimulus cycle [1/s], and baseline of EEG was the averaging 100 [ms] before the stimulus. Large evoked potential is observed at 300 [ms] after the stimulus and there were high correlation coefficients (from 0.855437[O2 electrode] to 0.975286[C3 electrode]) in all electrodes between AEP and EEG which is reduced SEP from S-AEP. Moreover, in both EEG the topography of N100 and P200 were corresponding. The summation characteristics of AEP and SEP were able to be shown from the above mentioned result. According to above results summation characteristics of SEP and AEP were confirmed.