Evoked Vertex and Inferior Colliculus Responses to Electrical Stimulation of the Cochlear Nucleus

Evoked potentials were recorded from the vertex and the inferior colliculus in guinea pigs in response to electrical stimulation of the cochlear nucleus complex. The stimuli consisted of 80-μs biphasic pulses, ranging from 20 to 5,000 μA. The effect of electrode location (nerve root area, surface, and in-depth dorsal cochlear nucleus) on the evoked response was assessed by measuring amplitudes, latencies, and thresholds as a function of stimulating current levels. Stimulation of the nerve root area resulted in the shortest latencies, the largest amplitudes, and the lowest thresholds, whereas the surface of the dorsal cochlear nucleus was the least effective stimulating site.