Frequency-invariant representation of interaural time differences

Abstract

Event Abstract Back to Event Frequency-invariant representation of interaural time differences Hannes Luling1, 2*, Ida Siveke1, Benedikt Grothe1 and Christian Leibold1 1 Ludwig-Maximilians-Universitat, Germany 2 BCCN, Germany The difference in traveling times of a sound from its origin to the two ears is called the interaural time difference (ITD). ITDs are the main cue for low-frequency-sound localization. The frequency of the stimulus modulates the ITD sensitivity of the response rates of neurons in the brain stem. This modulation is generally characterized by two parameters: The characteristic phase (CP) and the characteristic delay (CD). The CD corresponds to a difference in the temporal delays from the ears to a respective coincidence detector neuron. The CP is an additional phase offset the nature of which is still under debate. The two above characteristic quantities hence describe the best ITD at which a neuron responds maximally via (best ITD)=CD+CP/f. Here f describes the frequency of the pure tone stimulus. We recorded neuronal firing rates in the dorsal nucleus of the lateral lemniscus of the mongolian gerbil for pure tone stimuli with varying ITD and frequency. Interestingly, we found that CPs and CDs are strongly negatively correlated. To understand the observed distribution of CPs and CDs among the recorded population, we assessed the mutual information of firing rate and ITD in terms of these two parameters. We therefore computed signal and noise entropies from rate distributions fitted to the experiments. Our results show that the information-optimal distribution of CPs and CDs exhibits a similar negative correlation as the one observed experimentally. Assuming similar rate statistics, we make hypotheses about how CDs and CPs should optimally be distributed for mammals with various head diameters. As expected, the mutual information increases with head diameter. Moreover, for increasing head diameter the two distinct subclusters of high mutual information (peakers and troughers) fuse into one. To reveal correlations in the neural responses, we trained support vector machines (SVMs) and analyzed the resulting weights. We trained one SVM for every ITD interval. As input we used randomly drawn population rate vectors. We found that the error increases with number of different ITDs. For the behavioral localization acuity of 20 microseconds, we find a generalization error of about 0.6 percent. Moreover, ITDs are encoded by neural populations with strongly varying coding characteristics. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session II Citation: Luling H, Siveke I, Grothe B and Leibold C (2010). Frequency-invariant representation of interaural time differences. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00305 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 07 Mar 2010; Published Online: 07 Mar 2010. * Correspondence: Hannes Luling, Ludwig-Maximilians-Universitat, Munchen, Germany, lueling@bio.lmu.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Hannes Luling Ida Siveke Benedikt Grothe Christian Leibold Google Hannes Luling Ida Siveke Benedikt Grothe Christian Leibold Google Scholar Hannes Luling Ida Siveke Benedikt Grothe Christian Leibold PubMed Hannes Luling Ida Siveke Benedikt Grothe Christian Leibold Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.