Processing and stereophonic presentation of physiological signals.

Since the inception of electroencephalography (EEG), several devices have been built that make brain waves audible; they are known as electroencephalophones (EEP). None has so far taken advantage of the human binaural hearing capability. The system described here presents an effective stereophonic display of four channels of EEG, each from one quadrant of the skull. The signals from the two front quadrants are represented by a single tone whose pitch varies about a center frequency of 1250 Hz and which appears to move laterally in auditory space. The signals from the two occipital quadrants are similarly represented about center frequency of 700 Hz, so that they are readily distinguished from frontal activity. All channels are played through a single pair of headphones. The left headphone represents the combined activity of the two left-hand quadrants; the right headphone, of the two right-hand quadrants. The scheme may be used to supplement conventional graphic EEG records; under special conditions (e. g., routine monitoring, sleep research, training,) it may replace them altogether. Moreover, it may be adapted to vector electrocardiography (EKG) and even to the presentation of signals other than physiological, for instance in seismography.