Far Field Electrocochleography, Electrode Positions

Abstract

A systematic search proved that activity belonging to the far field electrocochleogram can be detected all over the head, including the tip of the nose. Of greatest interest are the tracings from the Vertex and the mastoid. The CM is present at both sites, but largest at the mastoid and with a phase difference of less than 90°, while the AP shows complete phase reversal. From 2.6—5.6 msec the Vertex exhibits three peaks. At the mastoid the counterpart of the first two is a single wave, while the third peak is distinct and homophasic. Around 7 msec there is a characteristic potential at the Vertex, which can be traced close to the subjective threshold. Optimum recording configurations are as follows: For the CM, mastoid versus contralateral side of the neck. For the AP, Vertex versus mastoid. For the 7 msec potential (FFP7), Vertex versus homolateral side of the neck.