Electrical activity of anterior parts of the visual system obtained by nasopharyngeal recordings.

Electrical responses to single flashes were recorded from the epipharynx and from various intranasal locations by withdrawing a nasopharyngeal electrode through the nose. The anatomical relation between the electrode and the eye ball was checked by taking an X-ray of the subject's skull. In the epipharynx and in the anterior part of the nose the responses were ERGs (a-wave, b-wave, wavelets) which were inverted in polarity. The reversal in polarity occurred when the electrode tip was underneath the posterior pole of the eye. At this electrode position and further back to the epipharynx high-frequency oscillations of increased amplitude and different waveform were recorded. It is concluded that components that change their polarity are generated by retinal dipoles oriented parallel with the electrode path while the increased oscillations recorded in the back of the nose are generated in the optic nerve by dipoles of vertical orientation.