Sensitivity to Interaural Time Differences Conveyed in the Stimulus Envelope: Estimating Inputs of Binaural Neurons Through the Temporal Analysis of Spike Trains.
Sound-source localization in the horizontal plane relies on detecting small differences in the timing and level of the sound at the two ears, including differences in the timing of the modulated envelopes of high-frequency sounds (envelope interaural time differences (ITDs)). We investigated responses of single neurons in the inferior colliculus (IC) to a wide range of envelope ITDs and stimulus envelope shapes. By a novel means of visualizing neural activity relative to different portions of the periodic stimulus envelope at each ear, we demonstrate the role of neuron-specific excitatory and inhibitory inputs in creating ITD sensitivity (or the lack of it) depending on the specific shape of the stimulus envelope. The underlying binaural brain circuitry and synaptic parameters were modeled individually for each neuron to account for neuron-specific activity patterns. The model explains the effects of envelope shapes on sensitivity to envelope ITDs observed in both normal-hearing listeners and in neural data, and has consequences for understanding how ITD information in stimulus envelopes might be maximized in users of bilateral cochlear implants-for whom ITDs conveyed in the stimulus envelope are the only ITD cues available.
Medizinische Physik and Cluster of Excellence Hearing4all, Universität Oldenburg, 26111, Oldenburg, Germany. mdietz@uwo.ca.|UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK. mdietz@uwo.ca.|National Centre for Audiology, Faculty of Health Sciences, Western University, London, N6G 1H1, Ontario, Canada. mdietz@uwo.ca.
Mathias
M
Dietz
Center for Computational Neuroscience and Neural Technology, Boston University, Boston, MA, 02215, USA.
Le
L
Wang
UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.
David
D
Greenberg
UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.|Dept. of Lingustics, Australian Hearing Hub, Macquarie University, Sydney, NSW, 2109, Australia.
David
D
McAlpine
D000818:Animals; D006168:Guinea Pigs; D007245:Inferior Colliculi / Q000502:physiology*; D008954:Models, Biological; D009474:Neurons / Q000502:physiology*; D013017:Sound Localization / Q000502:physiology*; D055366:Synaptic Potentials; D013997:Time Factors
auditory modeling; binaural; extracellular recordings; inferior colliculus; interaural time difference