The ventral cochlear nucleus is the first processing center for auditory signals in the central nervous system. Here, Cajal shows how individual auditory nerve fibers enter the cochlear nucleus ventrally as the cochlear nerve (A), bifurcating to form ascending and descending branches. The ascending branches (B) give rise to complex axonal terminals, the Calyces of Held, which synapse onto bushy cells to facilitate rapid, high-fidelity synaptic signals crucial to precise transmission of acoustic information. The descending branches travel posteriorly, giving rise to synapses in both the ventral (C) and dorsal (D) cochlear nucleus subdivisions that will perform more complex auditory processing, integrating feedback signals from deeper parts of the auditory pathway together with input from the cochlear nerve. 

3D print by Jeremy Swan based on an original illustration by Santiago Ramon y Cajal. Courtesy of the Cajal Institute, Spanish National Research Council or CSIC©