Areas of Interest
Neuroscience of the auditory system; computational neuroscience
of single neurons and neural systems; otolaryngology research
using otoacoustic emissions; biomedical engineering.
Our research seeks to integrate systems-neuroscience
experimental investigations with mathematical modeling.
Neurophysiological methods include single-unit recording of
neurons in the auditory system of awake animals. Modeling
methods include digital computer simulations at each of the
following levels: ion channels, synapses distributed over the
dendrites and soma, single neurons and multi-neuron neural
systems.
Lab Rotation Projects
(in collaboration with Dr. S. Kuwada)
Neural coding of auditory distance
Localizing sounds is important to humans and animals for
basic functions such as escape from a threat, capturing a prey,
and communication. Neural mechanisms for localizing sounds in
two-dimensions, horizontal (azimuth) and vertical (elevation)
angles, have been studied extensively. In contrast, mechanisms
responsible for localization of distance, the third spatial
dimension, are poorly understood. A stimulus of any modality
(auditory, visual or tactile) presented at a close distance is
particularly potent in evoking a defensive response. This
suggests that the brains of humans and animals can recognize
distance of a sensory stimulus (including sound) particularly
when the stimulus is nearby.
The present study is designed to break a new ground by
investigating how the brain processes auditory distance.
Physiologically, we will measure how neurons in the rabbit
midbrain encode auditory distance. The hypothesis is that
neurons of the inferior colliculus (IC) convey information about
auditory distance based on a ratio of direct to reverberant
signal amplitudes (D/R ratio). We have recorded binaural room
impulse responses (BRIRs) of the rabbit in a reverberant
acoustic chamber. Analysis of the BRIR acoustic signals indicate
that D/R ratio systematically changes as a function of auditory
distance. In this research, virtual sound fields (with a sound
source at a variable location) will be created by combining
BRIRs with a source signal and presented to the rabbit.
Responses of single neurons in the midbrain of unanesthetized
rabbits will be recorded in response to virtual sound fields.
Our preliminary observations indicate that the IC neurons
exhibit sensitivity to auditory distance.
The knowledge to be gained from this study should be useful
in future efforts to maximize the rehabilitative potential of
hearing-impaired patients so that optimal performance can be
achieved in tasks involving the binaural localization system
such as recognizing speech in a noisy cocktail-party setting.
Selected Publications
Bishop B, Kim DO, Sterbing-D'Angelo S, Kuwada S (2009).
Acoustic cues for sound localization measured in a rabbit and a
tennis ball and computed using a rigid sphere model, Assoc. Res.
Otolaryn. Midwinter Meeting Abstract No. 908.
Kim DO, Moiseff A, Turner JB, Gull J (2008). Acoustic cues
underlying auditory distance in barn owls, Acta Otolaryngol.
128: 382-387.
Choi Y-S, Lee S-Y, Parham K, Neely ST, Kim DO (2008).
Stimulus-frequency otoacoustic emission: Measurements in humans
and simulations with an active cochlear model, J. Acoust. Soc.
Am. 123: 2651-2669.
Kim DO, Yang XM, Ye Y (2003). A subpopulation of dorsal raphe
nucleus neurons retrogradely labeled with cholera toxin-B
injected into the inner ear. Exp Brain Res. 153: 514-521.
Kim DO, Yang XM, Neely DO (2003). Effects of the medial
olivocochlear reflex on cochlear mechanics: Experimental and
modeling studies of DPOAE. In Biophysics of the Cochlea: From
Molecules to Models, A.W. Gummer, World Scientific, New Jersey,
pp 506-516.
Warr WB, Beck-Boche JE, Ye Y, Kim DO (2002). Organization of
olivocochlear neurons in the cat studied with the retrograde
tracer cholera toxin-B. J. Assoc. Res. Otolar. 3: 457-478.
Parham K, Sun XM, Kim DO. (2001). Noninvasive assessment of
auditory function in mice: auditory brainstem response and
distortion product otoacoustic emission. In Handbook of Mouse
Auditory Research, JF Willott, Ed., CRC Press, pp 37-58.
Kim DO, Dorn PA, Neely ST, Gorga MP. (2001). Adaptation of
distortion product otoacoustic emission in humans. J. Assoc.
Res. Otolar. 2: 31-40.
Kim DO, D'Angelo WR. (2000). Computational model for the bushy
cell of the cochlear nucleus. Neurocomputing, 32-33, 189-196.
Revised 3/09 |
