Effects of somatosensory and parallel fiber stimulation on neurons in dorsal cochlear nucleus Kevin A. Davis, Roger L. Miller, and Eric D. Young, Effects of somatosensory and parallel fiber stimulation on neurons in dorsal cochlear nucleus. The short-latency inhibitory component precedes the evoked potential. The excitatory component occurs at the same latency as the evoked potential and probably reflects direct excitation of principal cells by granule cell axons. The excitatory component is seen in about half the type IV units for both stimulating sites.
Evidence suggests that it is produced by inhibitory input from cartwheel cells.
The appearance of this inhibitory component in almost all type IV units can be accounted for by the considerable spread of cartwheel-cell axons in the direction perpendicular to the parallel fibers. The evoked potential and all three components of the unit response vary systematically in size over the four pulses of the electrical stimulus. The facilitation resembles presynaptic facilitation and is seen with both MSN and parallel-fiber stimulation. A strong reduction in the granule cell response between the first and second pulse for MSN stimulation only. This reduction probably occurs presynaptically in the glomerulus or in the granule cell itself and could reflect inhibitory inputs.