.) The goal of this proposal is to determine the structural organization of central auditory pathways that process binaural information. The functional types of afferents that project to the central nucleus of the inferior colliculus are quite diverse and it is possible that single IC neurons integrate information from many afferent sources. At present there is insufficient information about the organization of these afferents to determine their contribution to receptive field properties and other response characteristics of binaural cells. One hypothesis is that axonal distribution and morphology are heterogeneous within iso-frequency planes. Thus, many different combinations of afferents would converge in synaptic zones and contribute to response properties of cells in those zones. A second hypothesis is that relative spatial relationships in iso-frequency regions of afferent nuclei are preserved by the organization of the projections to the inferior colliculus. The topology would provide a place code for binaural features. To address questions regarding the two hypotheses, a series of experiments detailing the organization of the afferent connections to the inferior colliculus in the adult cat are proposed.
Specific aims are: 1) to define the geometry of the afferent sheets and single axons of medial superior olivary projections to the IC using bulk and single axonal anterograde tracing methods; 2) to compare the geometry of converging axonal systems with the organization of the MSO axons with methods to co-label projections from more than one source in the same sections; and 3) to relate the distribution and morphology of intra-axonally labeled axons to response characteristics of electrophysiologically identified cells sending axons to IC. The results will lead to further hypotheses about the organization of axonal interactions and their relationship to binaural processing in the IC. Binaural processing is important for sound localization, coding of complex features of speech sounds and for phenomena such as masking and signal detection. Improving assessment of these functions in hearing impaired individuals requires experiments such as the one proposed to increase our knowledge about the anatomical and physiological basis for neural processing of sound.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000813-03
Application #
3217510
Study Section
Hearing Research Study Section (HAR)
Project Start
1990-09-30
Project End
1995-08-31
Budget Start
1992-09-01
Budget End
1993-08-31
Support Year
3
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Wake Forest University Health Sciences
Department
Type
Schools of Medicine
DUNS #
041418799
City
Winston-Salem
State
NC
Country
United States
Zip Code
27106
Alvarado, Juan Carlos; Fuentes-Santamaria, Veronica; Henkel, Craig K (2009) Rapid modifications in calretinin immunostaining in the deep layers of the superior colliculus after unilateral cochlear ablation. Hear Res 247:78-86
Fuentes-Santamaria, V; Alvarado, J Carlos; Henkel, C K et al. (2007) Cochlear ablation in adult ferrets results in changes in insulin-like growth factor-1 and synaptophysin immunostaining in the cochlear nucleus. Neuroscience 148:1033-47
Alvarado, Juan Carlos; Fuentes-Santamaria, Veronica; Franklin, Samuel R et al. (2007) Synaptophysin and insulin-like growth factor-1 immunostaining in the central nucleus of the inferior colliculus in adult ferrets following unilateral cochlear removal: a densitometric analysis. Synapse 61:288-302
Varga, R; Avenarius, M R; Kelley, P M et al. (2006) OTOF mutations revealed by genetic analysis of hearing loss families including a potential temperature sensitive auditory neuropathy allele. J Med Genet 43:576-81
Alvarado, J C; Fuentes-Santamaria, V; Franklin, S R et al. (2005) Unilateral cochlear ablation in adult ferrets results in upregulation in calretinin immunostaining in the central nucleus of the inferior colliculus. Neuroscience 136:957-69
Fuentes-Santamaria, Veronica; Alvarado, Juan Carlos; Taylor, Anna R et al. (2005) Quantitative changes in calretinin immunostaining in the cochlear nuclei after unilateral cochlear removal in young ferrets. J Comp Neurol 483:458-75
Henkel, C K; Gabriele, M L; McHaffie, J G (2005) Quantitative assessment of developing afferent patterns in the cat inferior colliculus revealed with calbindin immunohistochemistry and tract tracing methods. Neuroscience 136:945-55
Alvarado, Juan Carlos; Fuentes-Santamaria, Veronica; Henkel, Craig K et al. (2004) Alterations in calretinin immunostaining in the ferret superior olivary complex after cochlear ablation. J Comp Neurol 470:63-79
Varga, R; Kelley, P M; Keats, B J et al. (2003) Non-syndromic recessive auditory neuropathy is the result of mutations in the otoferlin (OTOF) gene. J Med Genet 40:45-50
Huang, Qing-Yang; Shen, Hui; Deng, Hong-Yi et al. (2003) Linkage and association of the CA repeat polymorphism of the IL6 gene, obesity-related phenotypes, and bone mineral density (BMD) in two independent Caucasian populations. J Hum Genet 48:430-7

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