Brain computer interface by use of electroencephalograms from right frontal area

In order to develop a brain computer interface (BCI), some of the present authors have investigated the brain activity during human recognition of characters and symbols representing directional meaning. They have recorded electroencephalograms (EEGs) from subjects viewing four types of arrows: “↑”, “↓”, “←” and “→” that were presented on a CRT. The arrows denote direction for upward, downward, leftward and rightward, respectively. Subjects were asked to read them silently. 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, ECDs were localized to areas related to the working memory for spatial perception, i. e. the right upper or the right middle frontal areas. And the opposite directional arrows had opposite dipoles in these areas. Taking into account these facts, the authors investigated a single trial EEGs of the subject precisely after the latency at 400ms, and determined effective sampling latencies for the discriminant analysis to four types of arrows. We sampled EEG data at latencies from 400ms to 900ms at 25ms intervals by the four channels such as Fp2, F4, C4 and F8. Data were resampled -1ms and -2ms backward. Results of the discriminant analysis with jack knife method for four types objective variates, the mean discriminant rate for seven sample subjects was almost 85 %.