Development of simultaneous measurement techniques for event-related fMRI and EEG and observation of the activation process of P300

In this study, techniques to measure EEG and fMRI simultaneously were investigated and P300 responses evoked by visual stimuli were examined. Event-related analysis was applied to combine the high temporal resolution of the EEG with the high spatial resolution of the fMRI, which may allow estimation of the temporal change in the activation of multiple cortical areas. A time scheme of stimulus presentation combined with an MRI scan was designed, taking into consideration the temporal delay between the generation of the P300 potential and the BOLD response. Three pattern oddball paradigm using standard, target and novel letter stimuli was performed, a technique in which subjects responded to rare target-letters but not to frequent standard- and rare novel-letters. Noises arising from the MRI scan and cardio-ballistic artifacts were removed from the raw data of the EEG by subtraction of the time-averaged waveforms of those artifacts. In comparing the grand average response of the EEG evoked by target events with those evoked by standard events, a significant difference was found in latency range from 280 to 450 ms (P<;;0.001). This enlarged response to the target was found to correspond to the late component, i.e., P3b, of P300. In the 14-subject group study of BOLD responses, significant activation appeared in the occipital, parietal and temporal regions and the prefrontal cortex, some of which showed a laterality of right-hemisphere dominance. Based on the results of EEG topography during the period of P3b response, a temporal progression of the activation from the occipital visual cortex via the temporoparietal and temporal regions to the prefrontal cortex was estimated. electronic document is a "live" template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.