Usefulness of computer-assisted portable EEG recorder for field work in applied human science.

Quantitative analysis of EEG frequencies provides useful information about the arousal level of the awake human (Matousek and Petersén, 1983; Okawa et al., 1984). It has been reported that the arousal level can be evaluated by measuring characteristics of power spectral densities in the range of alpha waves (Hyoki et al., 1993; Michimori et al., 1994; Ogilvie et al., 1991; Torsvall and Åkerstedt, 1987). In laboratory experiments, EEG measurements have been conducted using conventional clinical EEG recorders furnished in the room. However, there are some disadvantages to the conventional clinical EEG recorder despite its generally recognized usefulness, such as, limited availability in clinical setting, adverse effects on the emotional state of the subject, and economic cost (Ebersole and Leroy, 1983). In field study, for example, a study aimed at evaluating the arousal level of the community-dwelling elderly in their daily life at the time of a health check-up, it was difficult to provide a conventional clinical EEG recorder because of transportation difficulty and measurement complexity. Recently, a computer-assisted, economically priced, portable EEG recorder was developed for possible use in academic studies. This EEG recorder is commercially available, and is marketed under the name Brain Machine Interface (BMI, Nouryoku Kaihatsu Kenkyujyo, Tokyo). BMI is a portable one-channel EEG recording apparatus that is connected to a personal computer. Two electrodes are attached to a plastic hair band, and one electrode is attached to an ear with a short lead wire. As there is little available data to ascertain the reliability of EEG frequencies measured using this apparatus, in the present study we aimed to determine the reliability of measurement of this apparatus by comparing the BMI EEG frequency structure with that from a conventional clinical EEG recorder. Sixteen healthy male adult subjects voluntarily participated in this study after informed consent. The mean age was 32.8 ± 10.3 years. Subjects were synchronized to a sleep cycle from midnight to 7 o’clock for one week before the day of the experiment. On that day, subjects were seated in a comfortable chair, in a bright, electrically shielded, sound-attenuated room. The room air temperature was controlled at 25 ± 1.0°C, and (Appl Human Sci, 17 (4): 149-150, 1998)