Abstract
Characteristic changes in background EEG with the variation in reaction time were investigat ed. In the experiment, visual stimuli to proactively reduce the arousal level were presented repeatedly (5min.), followed by the presentation of repeated visual stimuli (15 times) to which the subjects were required to respond. These consecutive presentations (1 session) were repeated four times. From analysis of the seven subjects in whom the alpha waves were clearly observed, when comparing the final session with the first, results indicated a decrease in the subjective rating scores of “consciousness” and “concentration”, an increase in “fatigue”, and delay in reaction time, thereby suggesting a difference in the subjective and behavioral arousal level between sessions. Then, from comparison of these sessions, as a result of the analysis of EEG prior to the response demand stimulus, the peak frequency in alpha wave band decreased in the parietal region, and the theta 2 and alphal band power increased over nearly the entire scalp region, in the reaction time delay session. Moreover, the frequency fluctuation in alpha wave band tended to disappear. In conclusion, these characteristics of EEG provide clues to develop a simple and objective method for evaluating the arousal level in future.
