The broad objective of this project is to describe the brain's specializations for sound localization. The initial specific aim of the present application is to evaluate the ascending afferent representation of spectrum-based localization cues that are generated by directional properties of the head and outer ear. These filtering effects are known as the head-related transfer function (HRTF). It is hypothesized that this complex acoustic information is encoded by the discharge rates of a select population of inferior colliculus neurons, the type O units. Subsequent aims will expand upon this hypothetical construct of a functionally segregated spectral processing pathway to determine how neural representations of the HRTF are enhanced by descending efferent influences and learned listening strategies. Electrophysiological experiments will record single-unit responses to virtual space stimuli that simulate the natural directional properties of the HRTF with headphones. Related psychophysical experiments will confirm the functional significance of observed physiological mechanisms by measuring the effects of spectral pathway lesions on sound localization behavior. Electrophysiological studies in behaviorally conditioned cats will explore the mechanisms for adaptive listening under training contingencies that bias the information content of individual features of the HRTF. The spectral shapes that contribute to sound localization are closely related to the sounds of human speech. Consequently, this research will enhance our current understanding of the processes and perceptions that shape directional hearing, speech processing, and compensation for hearing loss in humans. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
2R01DC000954-11A1
Application #
6824485
Study Section
Auditory System Study Section (AUD)
Program Officer
Luethke, Lynn E
Project Start
1990-12-01
Project End
2009-06-30
Budget Start
2004-07-01
Budget End
2005-06-30
Support Year
11
Fiscal Year
2004
Total Cost
$321,895
Indirect Cost
Name
Johns Hopkins University
Department
Otolaryngology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Reiss, Lina A J; Ramachandran, Ramnarayan; May, Bradford J (2011) Effects of signal level and background noise on spectral representations in the auditory nerve of the domestic cat. J Assoc Res Otolaryngol 12:71-88
Lauer, Amanda M; May, Bradford J; Hao, Ziwei Judy et al. (2009) Analysis of environmental sound levels in modern rodent housing rooms. Lab Anim (NY) 38:154-60
May, Bradford J; Anderson, Michael; Roos, Matthew (2008) The role of broadband inhibition in the rate representation of spectral cues for sound localization in the inferior colliculus. Hear Res 238:77-93
Davis, Kevin A; Ramachandran, Ramnarayan; May, Bradford J (2003) Auditory processing of spectral cues for sound localization in the inferior colliculus. J Assoc Res Otolaryngol 4:148-63
May, Bradford J; Prosen, Cynthia A; Weiss, Donna et al. (2002) Behavioral investigation of some possible effects of the central olivocochlear pathways in transgenic mice. Hear Res 171:142-157
May, B J (2000) Role of the dorsal cochlear nucleus in the sound localization behavior of cats. Hear Res 148:74-87