Areas of Interest:
Neuroscience of the auditory system
Computational neuroscience of single neurons and neural systems
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, single neurons, neural circuits, and the auditory system.
Coding of sound-source location (azimuth and distance) and sound pattern in the midbrain (in collaboration with Dr. S. Kuwada)
In natural environments, a listener has to simultaneously identify the location (where) and content (what) of a sound. In natural environments, reverberation disrupts both sound location and the content. Our research investigates midbrain neurons’ coding of sound location and content. A key feature for recognition is the fluctuations in amplitude, i.e., amplitude modulations present in natural sounds such as speech. We record single neuron spike activities of the midbrain in un-anesthetized rabbits. We use the virtual auditory space methods to present sounds at different azimuths and distances in environments containing varying strengths of reverberation.
Except for our recent study, no other neural study has investigated jointly the effects of reverberation on localization and modulation envelope coding. Our preliminary findings indicate that it is greatly important to study jointly the effects of reverberation on localization and envelope coding. We have also found that some neurons are resistant to reverberation in both azimuth and envelope coding, while others are resistant for azimuth coding only, and still others resistant for envelope coding only. We have also observed neurons where reverberation enhances the coding of azimuth and/or envelope. Such neurons may serve to mitigate the deleterious effects of reverberation on “what’ and “where” processing of sounds.
The clinical relevance of our proposed studies is that localization and recognition in reverberation is a major challenge to the hearing impaired and aging populations. Our findings suggest that coding of envelope in high frequency neurons may be beneficial for envelope processing in reverberation. For people with high-frequency hearing loss (e.g., presbycusis), the loss of high-frequency hearing and the degraded ability of the remaining low-frequency neurons may account for much of the difficulty in speech recognition in reverberation.
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 localizing and
recognizing speech in noisy reverberant settings such as a cocktail party.
Kim DO, Zahorik P, Bishop B, Kuwada S,. (2013) Effect of reverberation on acoustic measures relevant for localization (where) and recognition (what) of sounds located at various azimuths and distances: a study of humans and rabbits. Assoc Res Otolaryn Meeting.
Kuwada S, Bishop B, Kim DO (2012) Approaches to the study of neural coding of sound source location and sound envelope in real environments. Frontiers in Neural Circuits Vol 6, Article 32; DOI: 10.3389/fncir.2012.00042
Kim DO, Kuwada S, Bishop B, Zahorik P. (2012) Acoustic modulation transfer functions for human listeners in anechoic and reverberant environments. Assoc Res Otolaryn Meeting. Kuwada S, Bishop B, Alex C, Condit DW, Kim DO. (2011) Spatial tuning to sound-source azimuth in the inferior colliculus of unanesthetized rabbit. J Neurophysiol 106:(5) 2698-2708. PMID: 218496
Zahorik P, Kim DO, Kuwada S, Anderson PW, Brandewie E, Collecchia R, Srinivasan N (2012). Amplitude modulation detection by human listeners in reverberant sound fields: carrier bandwidth effects and binaural versus monaural comparison. Proceedings of Meetings on Acoustics Vol. 15, No. 050002; DOI: 10.1121/1.4733848
,, , , Amplitude modulation detection by human listeners in sound fields. Proceedings of Meetings on Acoustics 12: 050005, 6 pages. DOI: 10.1121/1.3656342.,
Kim, DO, Bishop, B and Kuwada, S. (2010) Acoustic cues for sound source distance and azimuth in rabbits, a racquetball and a rigid spherical model. J Assoc Res Otolaryngol 11: 541-557. PMID: 20526728
Kuwada, CA, Bishop, B, Kuwada, S and Kim, DO (2010) Acoustic recordings in human ear canals to sounds at different locations. Otolaryngology-Head and Neck Surgery. 142: 615-617. PMID: 20304288
Fitzpatrick, DC, Roberts JM, Kuwada, S, Kim, DO and Filipovic, B (2009) Processing temporal modulations in binaural and monaural auditory stimuli by neurons in the inferior colliculus and auditory cortex. J. Assoc. Res. Otolaryngol. 10: 579-593. PMID: 19506952
Kim DO, Moiseff A, Turner JB, Gull J. (2008). Acoustic cues underlying auditory distance in barn owls. Acta Oto-Laryngol. 128: 382-387. PMID: 18368570
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: 2561-2669. PMID: 18529185
Ghoshal, S. and Kim, D.O. (1997). Marginal shell of the anteroventral cochlear nucleus: Single-unit response properties in the unanesthetized decerebrate cat. J. Neurophysiol. 77, 2083-2097. PMID: 9114257
Kim, D.O., Ghoshal, S., Khant, S.L., and Parham, K. (1994). A computational model with ionic conductances for the fusiform cell of the dorsal cochlear nucleus. J. Acoust. Soc. Am. 96, 1501-1514. PMID: 7963015
Arle, J.E. and Kim, D.O. (1991). "Simulations of cochlear nucleus neural circuitry: Excitatory-inhibitory response area types I-IV" J. Acoust. Soc. Am. 90, 3106-3121. PMID: 1787249
Neely, S.T. and Kim, D.O.(1986). " A model for active elements in cochlear biomechanics,” J. Acoust. Soc. Amer. 79: 1472‑1480. PMID: 3711446
Kim, D.O.(1986). "Active and nonlinear cochlear biomechanics and the role of outer‑hair‑cell subsystem in the mammalian auditory system," Hearing Res. 22: 105‑114. PMID: 2426235
Siegel, J.H. and Kim, D.O.(1982). "Efferent neural control of cochlear mechanics? Olivocochlear bundle stimulation affects cochlear biomechanical nonlinearity," Hearing Res. 6: 171‑182. PMID: 7061350
Kim, D.O., Molnar, C.E. and Matthews, J.W.(1980). "Cochlear mechanics: nonlinear behavior in two‑tone responses as reflected in cochlear‑nerve‑fiber responses and in ear‑canal pressure," J. Acoust. Soc. Amer. 67: 1704‑1721.