Projections of Cochlear Nucleus to Superior Olivary Complex in an Echolocating Bat: Relation to Function
Studies of comparative neuroanatomy provide information about structural variations that in turn can be clues to function. It is in this spirit that we use the mustached bat Pteronotus parnellii as our example in this paper on the inputs from the cochlear nucleus to the superior olivary complex. We will show that the projections from the cochlear nucleus to the lateral superior olive (LSO) are virtually identical to those of other mammals, but the projections to the medial superior olive (MSO) are different in that the ipsilateral input is extremely sparse. We shall propose that this difference is in the proportion of the ipsilateral to contralateral inputs, not that there is a unique input to the MSO of the mustached bat. We will focus on the functional consequences of the unusual pattern of inputs to MSO. We will argue that one of the consequences of the bat’s adaptations for echolocation is the evolution of the MSO into a structure in which a difference in projections from one cochlear nucleus produces great functional differences.
KeywordsInferior Colliculus Cochlear Nucleus Good Frequency Echolocation Call Interaural Level Difference
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- Bledsoe, S.C.J., Snead, C.R., Helfert, R.H., Prasad, V., Wenthold, R.J., and Atlshuler, R.A., 1990, immunocytochemical and lesion studies support the hypothesis that the projection from the medial nucleus of the trapezoid body to the lateral superior olive is glycinergic, Brain Res., 517:189–194.PubMedCrossRefGoogle Scholar
- Casseday J.H., and Covey E., 1987, Central auditory pathways in directional hearing, in: “Directional Hearing,” W. Yost, and G. Gourevitch, ed., Springer, New York.Google Scholar
- Friauf, E., and Ostwald, J., 1988, Divergent projections of physiologically characterized rat ventral cochlear nucleus neurons as shown by intra-axonal injection of horseradish peroxidase, Exp. Brain. Res., 73:263–284.Google Scholar
- Grothe, B., 1990, “Versuch einer Definition des medialen Kernes des oberen Olivenkomplexes bei der Neuwelt fledermaus Pteronotus p. parnellii,” Ph.D. dissertation, Ludwig-Maximilians-Universität, Munich.Google Scholar
- Harrison J.M., and Feldman M.M., 1970, Anatomical aspects of the cochlear nucleus and superior olivary complex, in: “Contributions to Sensory Physiology, Vol. 4,” W. D. Neff, ed., Academic, New York.Google Scholar
- Kuwabara, N., and Zook, J.M., 1992, Projections to the medial superior olive from the medial and lateral nuclei of the trapezoid body in rodents and bats, J. Comp. Neurol., in press.Google Scholar
- Kuwada, S., and Yin, T.C.T., 1987, Physiological studies of directional hearing, in: “Directional Hearing,” W. A. Yost, and G. Gourevitch, ed., Springer-Verlag, New York.Google Scholar
- Lindsey, B.G., 1974, Fine structure and distribution of axon terminals from the cochlear nucleus on neurons in the medial superior olivary nucleus of the cat, J. Comp. Neurol., 16:81–104.Google Scholar
- Schwartz I.R., 1984, Axonal organization in the cat medial superior olivary nucleus, in: “Contributions to Sensory Physiology, Vol. 8,” W. D. Neff, ed., New York.Google Scholar
- Warr W.B., 1982, Parallel ascending pathways from the cochlear nucleus: Neuroanatomical evidence of functional specialization, in: “Contributions to Sensory Physiology, Vol. 7,” W. D. Neff, ed., Academic, New York.Google Scholar