RESEARCH:

Auditory Neurophysiology, Neural Circuitry and Information Processing, and Computational Neuroscience

Research in the Auditory Processing Laboratory investigates the encoding, representation, and transformation of acoustic information within the auditory system. The goal is to understand how the brain represents and perceives the acoustic environment and how the neural systems in the brain are organized to create this representation. Our approach combines single- and multi-unit recording and analysis techniques, pharmacological manipulations, and computer modeling studies.
Current interest centers on the inferior colliculus (IC) because it occupies a pivotal position in the central auditory system; it receives direct inputs from most, if not all, of the auditory nuclei in the brainstem and, in turn, provides nearly all of the input to the auditory forebrain. Anatomical evidence suggests that the projections to the IC form highly organized synaptic domains with both segregated and shared sources of input. In support of this parallel processing model, our recent electrophysiological studies have discovered three principal IC response types that appear to be uniquely specialized for the neural encoding of spectral cues for sound localization, narrowband signals in noise, and binaural level and timing information. Based on correlations with response properties in lower-order nuclei, it has been hypothesized that each IC unit type reflects a dominant excitatory input from the medial superior olive, the lateral superior olive, or the dorsal cochlear nucleus. We are now performing experiments designed to provide direct evidence for these functional connections. In addition, we are exploring the functional consequences of this synaptic organization by comparing the quality of acoustic representations in IC target neurons and their sources of input. A question of particular interest in these latter experiments is how the ascending inputs to the IC interact with each other and a rich intrinsic inhibitory circuitry to enhance the processing of sound localization information.

RECENT PUBLICATIONS:

DAVIS KA., RAMACHANDRAN R AND MAY BJ. Single unit responses in the inferior colliculus of decerebrate cats: II. Sensitivity to interaural level differences. J Neurophysiol 82: 164-175, 1999.
SPIROU GA, DAVIS KA, NELKEN I AND YOUNG ED. Spectral integration by type II interneurons in dorsal cochlear nucleus. J Neurophysiol 82: 648-663, 1999.
DAVIS KA AND YOUNG ED. Pharmacological evidence of inhibitory and disinhibitory neuronal circuits in dorsal cochlear nucleus. J Neurophysiol 83: 926-940, 2000.
RAMACHANDRAN R, DAVIS KA AND MAY BJ. Rate representation of tones in noise in the inferior colliculus of decerebrate cats. JARO 1: 144-160, 2000.
YOUNG ED AND DAVIS KA. Circuitry and function of the cat dorsal cochlear nucleus. In: Integrative Functions in the Mammalian Auditory Pathway, edited by D Oertel, R Fay and A Popper. Springer-Verlag, 2002, pp. 160-206.
DAVIS KA. Evidence of a functionally segregated pathway from dorsal cochlear nucleus to inferior colliculus. J Neurophysiol 87: 1824-1835, 2002.
DAVIS KA, RAMACHANDRAN R AND MAY BJ. Auditory processing of spectral cues for sound localization in the inferior colliculus. JARO 4: 148-163, 2003.
DAVIS KA. Contralateral effects and binaural interactions in dorsal cochlear nucleus. JARO 6: 280-296, 2005.
DAVIS KA. Spectral processing in the inferior colliculus. In: Auditory Spectral Processing, edited by M Malmierca and D Irvine. San Diego: Elsevier Inc, 2005, pp. 169-205.
DAVIS KA, LOMAKIN O AND PESAVENTO MJ. Response properties of single units in the dorsal nucleus of the lateral lemniscus of decerebrate cats. J Neurophysiol 98: 1475-1488 2007.
LOMAKIN O AND DAVIS KA. On the role of the wideband inhibitor in the dorsal cochlear nucleus: A computational modeling study. JARO 9: 506-520, 2008. PMCID: PMC2580807.

• Greene NT, Davis KA. Discharge patterns in the lateral superior olive of decerebrate cats. J Neurophysiol. 2012 Oct; 108(7):1942-53.
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• Davis KA, Luo X, Mather PT, Henderson JH. Shape memory polymers for active cell culture. J Vis Exp. 2011; (53).
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• Davis KA, Burke KA, Mather PT, Henderson JH. Dynamic cell behavior on shape memory polymer substrates. Biomaterials. 2011 Mar; 32(9):2285-93.
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• Kanold PO, Davis KA, Young ED. Somatosensory context alters auditory responses in the cochlear nucleus. J Neurophysiol. 2011 Mar; 105(3):1063-70.
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• Greene NT, Lomakin O, Davis KA. Monaural spectral processing differs between the lateral superior olive and the inferior colliculus: physiological evidence for an acoustic chiasm. Hear Res. 2010 Oct 1; 269(1-2):134-45.
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• Lomakin O, Davis KA. On the role of the wideband inhibitor in the dorsal cochlear nucleus: a computational modeling study. J Assoc Res Otolaryngol. 2008 Dec; 9(4):506-20.
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• Davis KA, Lomakin O, Pesavento MJ. Response properties of single units in the dorsal nucleus of the lateral lemniscus of decerebrate cats. J Neurophysiol. 2007 Sep; 98(3):1475-88.
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• Davis KA. Contralateral effects and binaural interactions in dorsal cochlear nucleus. J Assoc Res Otolaryngol. 2005 Sep; 6(3):280-96.
  View in: PubMed
• Davis KA. Spectral processing in the inferior colliculus. Int Rev Neurobiol. 2005; 70:169-205.
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• Davis KA, Ramachandran R, May BJ. Auditory processing of spectral cues for sound localization in the inferior colliculus. J Assoc Res Otolaryngol. 2003 Jun; 4(2):148-63.
  View in: PubMed
• Davis KA. Evidence of a functionally segregated pathway from dorsal cochlear nucleus to inferior colliculus. J Neurophysiol. 2002 Apr; 87(4):1824-35.
  View in: PubMed
• Ramachandran R, Davis KA, May BJ. Rate representation of tones in noise in the inferior colliculus of decerebrate cats. J Assoc Res Otolaryngol. 2000 Sep; 1(2):144-60.
  View in: PubMed
• Davis KA, Young ED. Pharmacological evidence of inhibitory and disinhibitory neuronal circuits in dorsal cochlear nucleus. J Neurophysiol. 2000 Feb; 83(2):926-40.
  View in: PubMed
• Spirou GA, Davis KA, Nelken I, Young ED. Spectral integration by type II interneurons in dorsal cochlear nucleus. J Neurophysiol. 1999 Aug; 82(2):648-63.
  View in: PubMed
• Ramachandran R, Davis KA, May BJ. Single-unit responses in the inferior colliculus of decerebrate cats. I. Classification based on frequency response maps. J Neurophysiol. 1999 Jul; 82(1):152-63.
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• Davis KA, Ramachandran R, May BJ. Single-unit responses in the inferior colliculus of decerebrate cats. II. Sensitivity to interaural level differences. J Neurophysiol. 1999 Jul; 82(1):164-75.
  View in: PubMed
• Davis KA, Young ED. Granule cell activation of complex-spiking neurons in dorsal cochlear nucleus. J Neurosci. 1997 Sep 1; 17(17):6798-806.
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• Davis KA, Voigt HF. Evidence of stimulus-dependent correlated activity in the dorsal cochlear nucleus of decerebrate gerbils. J Neurophysiol. 1997 Jul; 78(1):229-47.
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• Hancock KE, Davis KA, Voigt HF. Modeling inhibition of type II units in the dorsal cochlear nucleus. Biol Cybern. 1997 Jun; 76(6):419-28.
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• Davis KA, Miller RL, Young ED. Effects of somatosensory and parallel-fiber stimulation on neurons in dorsal cochlear nucleus. J Neurophysiol. 1996 Nov; 76(5):3012-24.
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• Davis KA, Voigt HF. Computer simulation of shared input among projection neurons in the dorsal cochlear nucleus. Biol Cybern. 1996 May; 74(5):413-25.
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• Davis KA, Ding J, Benson TE, Voigt HF. Response properties of units in the dorsal cochlear nucleus of unanesthetized decerebrate gerbil. J Neurophysiol. 1996 Apr; 75(4):1411-31.
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• Davis KA, Gdowski GT, Voigt HF. A statistically based method to generate response maps objectively. J Neurosci Methods. 1995 Mar; 57(1):107-18.
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• Davis KA, Voigt HF. Neural modeling of the dorsal cochlear nucleus: cross-correlation analysis of short-duration tone-burst responses. Biol Cybern. 1994; 71(6):511-21.
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