Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The present study utilizes electrophysiological and neuroanatomical techniques to investigate the functional organization of the gustatory system in the brainstem and the forebrain of the channel catfish, Ictalurus punctatus. Neuroanatomical studies indicate an overlapping, segmental pattern of projection of glossopharyngeal-vagal branches in the vagal lobe. The vagal nerve complex is divisible into an interoceptive input (consisting of general visceral fibers) from abdominal viscera and an exteroceptive-branchial component (consisting of special and general visceral fibers) innervating the oro-pharyngeal region. The interoceptive-visceral input converges onto the exteroceptive, oro-pharyngeal input in the nucleus intermedius of the vagal lobe (nIV). In addition, extra-oral and oral gustatory information converges onto the nucleus intermedius of the facial lobe (nIF) and sensory inputs from separate regions of the oropharynx converge onto separate halves of the dorsal cap of the vagal lobe. Overlapping taste and tactile sensory maps of the oropharynx are present in the vagal lobe of the catfish. The representation of the oropharynx is less well defined than the somatotopic map in the facial lobe except for the bilaterally mapped extra-oral surface. Gustatory information reaches the area dorsalis pars medialis of the telencephalon and several nuclei in the ventral diencephalon of the catfish. The central gustatory pathway ascends from the medulla to the level of the diencephalon via the secondary gustatory nucleus as well as to the telencephalon via small neurons in the diencephalic lobo-bulbar nucleus. Neurons in the gustatory region of the telencephalon descend to the diencephalic level primarily via the medial forebrain bundle.