Two fundamental concepts unite the proposed projects. The first is that the topographic (tonotopic) organization characteristic of auditory nuclei reflects their basic functional organization. The second is that the auditory system is made up of multiple parallel pathways arising from different neuronal types. The proposed research is designed to relate the axonal arborization patterns of specific cell types to the three- dimensional frame of reference afforded by isofrequency contours. Eleven experiments are proposed to achieve four specific aims: 1) To characterize the organization of the bushy cell pathway from the cochlear nucleus to the superior olivary complex and from the superior olivary complex to the inferior colliculus. 2) To characterize the multipolar cell path way from the ventral cochlear nucleus to the inferior colliculus. 3) To analyze the periolivary cell groups of the superior olivary complex in terms of specific cell types. 4) To examine the organization of the isofrequency contours in the inferior colliculus in terms of the arborization patterns of lemniscal inputs from the bushy and multi-polar cell pathways and from selected periolivary nuclei. The fourth specific aim provides the framework for interpretation of the results of the other studies. The hypothesis is that, although a number of lower brain stem auditory pathways converge on one isofrequency contour in the inferior colliculus, their terminal arborizations occupy different domains within that contour. Methods to be used include: l) Tracing techniques based on the anterograde and/or retrograde transport of biocytin, Phaseolus vulgaris-leucoagglutin, and a number of different fluorescent dyes, and 2) A fixed slice preparation in which the dendritic arborization patterns of neurons that project to known sources can be examined. Intrinsic plexuses of axons within the inferior colliculus appear to coincide in position and extent with the isofrequency contours defined physiologically and will serve to represent those contours anatomically. Our long-term objective is to understand the organization of the brainstem auditory pathways in terms of connections among the multiple, different neuronal types that form them. Neuroanatomical studies provide information essential for reaching an understanding of the mechanisms of auditory processing. The neuronal activity that leads to functional expression is dependent on the precise and specific connectivities among hundreds of specialized neuronal types. Detailed explications of these connectivities will not only help to explain available functional data, it will provide a basis for developing rational hypotheses about auditory function that can be tested further.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000135-20
Application #
2733625
Study Section
Hearing Research Study Section (HAR)
Project Start
1978-07-01
Project End
2000-06-30
Budget Start
1998-07-01
Budget End
1999-06-30
Support Year
20
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Duke University
Department
Biology
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Cant, Nell B (2013) Patterns of convergence in the central nucleus of the inferior colliculus of the Mongolian gerbil: organization of inputs from the superior olivary complex in the low frequency representation. Front Neural Circuits 7:29
Cant, N B; Benson, C G (2008) Organization of the inferior colliculus of the gerbil (Meriones unguiculatus): projections from the cochlear nucleus. Neuroscience 154:206-17
Cant, Nell B; Benson, Christina G (2006) Organization of the inferior colliculus of the gerbil (Meriones unguiculatus): differences in distribution of projections from the cochlear nuclei and the superior olivary complex. J Comp Neurol 495:511-28
Schofield, B R; Cant, N B (1999) Descending auditory pathways: projections from the inferior colliculus contact superior olivary cells that project bilaterally to the cochlear nuclei. J Comp Neurol 409:210-23
Schofield, B R; Cant, N B (1997) Ventral nucleus of the lateral lemniscus in guinea pigs: cytoarchitecture and inputs from the cochlear nucleus. J Comp Neurol 379:363-85
Schofield, B R; Cant, N B (1996) Origins and targets of commissural connections between the cochlear nuclei in guinea pigs. J Comp Neurol 375:128-46
Schofield, B R; Cant, N B (1996) Projections from the ventral cochlear nucleus to the inferior colliculus and the contralateral cochlear nucleus in guinea pigs. Hear Res 102:1-14
Schofield, B R; Cant, N B (1992) Organization of the superior olivary complex in the guinea pig: II. Patterns of projection from the periolivary nuclei to the inferior colliculus. J Comp Neurol 317:438-55
Schofield, B R; Cant, N B (1991) Organization of the superior olivary complex in the guinea pig. I. Cytoarchitecture, cytochrome oxidase histochemistry, and dendritic morphology. J Comp Neurol 314:645-70
Schofield, B R (1991) Superior paraolivary nucleus in the pigmented guinea pig: separate classes of neurons project to the inferior colliculus and the cochlear nucleus. J Comp Neurol 312:68-76