Sites on termination on the saccular macula of auditory nerve fibers in the goldfish as determined by intracellular injection of procion yellow.

Procion yellow dye was injected intracellularly into large auditory fibers of goldfish to investigate the relationship between the response type of these fibers and their site of termination in the saccular macula. Fibers which responded to the rarefaction phases of sound were found to terminate on the hair cells located in the ventral half of the saccular macula, while those which responded to the compression phases were found to terminate on the dorsally located hair cells. A third group of fibers, which responded to both sound phases, was found to bifurcate outside the saccular macula and terminate on both dorsally and ventrally located hair cells. Some of the fibers of this group were found to trifurcate before entering the saccular macula. Results obtained in the present study, in conjunction with the findings on the orientation of hair cells within the sensory macula, can explain the mechanism underlying the presence of three different response types of fibers in the auditory nerve of the goldfish.