Fundamental research for brain machine interface by use of EEG from right frontal gyrus

In order to develop a brain machine interface, the authors have investigated the brain activity during human recognition of characters and symbols representing directional meaning. The authors have recorded electroencephalograms (EEGs) from subjects viewing four types of Kanji (Chinese characters being used currently in the Japanese language) and arrows that were presented on a CRT. Each denoted direction for upward, downward, leftward and rightward, respectively. Subjects were asked to read them silently. Regardless of the directions, the reaction time was almost equal. EEGs were averaged for each stimulus type and direction, and event related potentials (ERPs) were obtained. The equivalent current dipole source localization (ECDL) method has been applied to these ERPs. In both cases, no large difference was observed until 250 ms at their latencies, and after that ECDs were localized to areas related to the working memory for the spatial perception. Taking into account these facts, the authors have investigated a single trial EEGs precisely after the latency at 400ms, and have determined effective sampling latencies for the discriminant analysis on four types of arrows: ↑, ↓, ← and →. By a discriminant analysis, the results of discriminant rate are 100% for each subject and for each trial. These results show the possibility of using EEGs for a brain machine interface in four type controls.