Localizing a sound in 3-dimensional space requires the processing of azimuth, elevation, and distance. Although considerable attention has been focused on the neural processing of azimuthal and elevational cues, our knowledge of the neural processing of distance is almost non-existent. Psychophysical and modeling studies show distance perception in reverberant environments is based on the ratio of reverberant to direct sound energy. This ratio changes with distance because the direct energy decreases at 6 dB per for doubling of distance, but reverberant energy remains about constant with distance. Another cue for distance are the increases in interaural level difference with decreasing distance. Another potential cue is the systematic decrease in high frequency energy with increasing distance. To investigate the neural processing of sound distance, we will use virtual sounds made from ear canal recordings to sounds emanating from different distances and azimuths that are made in our state-of-the-art anechoic and reverberant chambers. In human listeners, such virtual sounds produce auditory images that are appropriately externalized and localized. We will use this virtual technology because, in comparison to making neural recordings in the real sound field, it allows the dissection and modification of auditory cues and also offers far greater efficiency and flexibility in sampling spatial locations. It also permits switching back and forth from the anechoic to reverberant environment, while recording from a neuron. We will explore distance processing in both anechoic and reverberant environments because the acoustics are quite different and both of these environments, to one degree or another, are normally experienced by humans and other animals.
Our aim i s to determine the neural coding of sound source distance in anechoic and reverberant environment in neurons of the inferior colliculus in the unanesthetized rabbit. Specifically, we will examine the effect of neural interactions between distance and azimuth, distance and acoustic environment, and azimuth and acoustic environment. The results may be helpful in designing hearing aids, cochlear implants, and robotic devices to incorporate all 3 dimensions of spatial hearing.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IFCN-B (02))
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Platt, Christopher
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University of Connecticut
Anatomy/Cell Biology
Schools of Medicine
United States
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Kuwada, Shigeyuki; Kim, Duck O; Koch, Kelly-Jo et al. (2015) Near-field discrimination of sound source distance in the rabbit. J Assoc Res Otolaryngol 16:255-62
Kim, Duck O; Zahorik, Pavel; Carney, Laurel H et al. (2015) Auditory distance coding in rabbit midbrain neurons and human perception: monaural amplitude modulation depth as a cue. J Neurosci 35:5360-72
Kuwada, Shigeyuki; Bishop, Brian; Kim, Duck O (2014) Azimuth and envelope coding in the inferior colliculus of the unanesthetized rabbit: effect of reverberation and distance. J Neurophysiol 112:1340-55
Zahorik, Pavel; Kim, Duck O; Kuwada, Shigeyuki et al. (2012) Amplitude modulation detection by human listeners in reverberant sound fields: Carrier bandwidth effects and binaural versus monaural comparison. Proc Meet Acoust 15:
Kuwada, Shigeyuki; Bishop, Brian; Alex, Caitlin et al. (2011) Spatial tuning to sound-source azimuth in the inferior colliculus of unanesthetized rabbit. J Neurophysiol 106:2698-708
Zahorik, Pavel; Kim, Duck O; Kuwada, Shigeyuki et al. (2011) Amplitude modulation detection by human listeners in sound fields. Proc Meet Acoust 12:50005-50010
Kim, Duck O; Bishop, Brian; Kuwada, Shigeyuki (2010) Acoustic cues for sound source distance and azimuth in rabbits, a racquetball and a rigid spherical model. J Assoc Res Otolaryngol 11:541-57
Fitzpatrick, Douglas C; Roberts, Jason M; Kuwada, Shigeyuki et al. (2009) Processing temporal modulations in binaural and monaural auditory stimuli by neurons in the inferior colliculus and auditory cortex. J Assoc Res Otolaryngol 10:579-93
Wang, S J; Furusho, M; D'Sa, C et al. (2009) Inactivation of fibroblast growth factor receptor signaling in myelinating glial cells results in significant loss of adult spiral ganglion neurons accompanied by age-related hearing impairment. J Neurosci Res 87:3428-37
D'Angelo, W R; Sterbing, S J; Ostapoff, E-M et al. (2005) Role of GABAergic inhibition in the coding of interaural time differences of low-frequency sounds in the inferior colliculus. J Neurophysiol 93:3390-400

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