Central organization of the electrosensory lateral line system in bullhead catfish Ictalurus nebulosus

The connections of the electrosensory lateral line lobe (ELL) of ictalurid catfish were examined by means of horseradish peroxidase tracing methods. The ELL receives direct input from the anterior and posterior lateral line nerves. Some of these nerve fibers continue through the ELL to end as mossy fibers in the lateral portion of the eminentia granularis. Granule cells in this area as well as those in lobus caudalis of the cerebellum project back to the ELL as parallel fibers in the upper molecular layer. The lower molecular layer of the ELL receives its input from the n. praeeminentialis. The ELL projects via the lateral lemniscus to the n. praeeminentialis and torus semicircularis bilaterally, but more heavily on the contralateral side. In addition, the n. praeeminentialis receives the bulk of its input from the ipsilateral torus semicircularis. The caudal lobe of the cerebellum both projects to the electrosensory portion of the torus semicircularis and receives indirect input from the torus semicircularis via the anterior olivary nucleus. In summary, the central organization of this ampullary receptor electrosensory system in catfish is similar to that of the ampullary-tuberous receptor electrosense of mormyrids and gymnotids.