Electrophysiological mapping of the cochlear nucleus with multi-channel bipolar surface microelectrodes

Auditory potentials in response to electrical stimulation of the cochlear nucleus were recorded in guinea pigs using two types of multi-channel surface microelectrodes with inter-electrode distance of 100 and 200 μm. Unequivocal waves of electrically evoked auditory brainstem responses (EABRs), which increased in amplitude with increasing stimulation current, were consistently observed. Electrophysiological mapping with these multichannel electrodes could clearly distinguish stimulation points showing positive EABRs from points showing undetectable EABRs, indicating that multi-channel surface microelectrodes have great potential in clinical use to determine the optimal location for the positioning of auditory brainstem implants, and may allow more precise discrimination of pitch. Further study to clarify the optimal inter-electrode distance for humans is necessary before application to physiological mapping in the human cochlear nucleus.