The Kim Auditory Neuroscience Laboratory 

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 systems.


Current Research Topic:
Coding of sound-source distance (in collaboration with Dr. S. Kuwada)

            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.
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       Recent articles:
Click on one of the following items to view the contents (descriptions of reasearch and publications).

Neurobiol. Auditory System

Computational Neuroscience

Otoacoustic Emissions