A system for evoking an electroencephalogram (EEG) signal from the brain of a user has a brain wave evoking terminal unit (2) which includes a headgear (4) for being mounted on the head of the user, a light emitter (6), mounted on the headgear (4), for applying an EEG signal evoking photic stimulus to the eyes of the user, and electrodes (50, 51, 52). mounted on the headgear (4), for detecting brain waves produced by the user. The system also has a brain wave signal processor (3), responsive to brain wave signals from the electrodes (50, 51, 52), for generating a stimulating signal having a frequency corresponding to a brain wave to be evoked, and for applying the stimulating signal to the light emitter (6). The brain wave to be evoked is extracted and fed back as stimulating light to the user, who can be rapidly and strongly brought into a desired brain wave condition. The brain wave signal processor (3) may be combined with the brain wave evoking terminal unit (2), so that the system is small in size, simple in arrangement, and can be carried and mounted on the user's head with ease.
System for evoking electroencephalogram signals.