Top-down influences on intensity coding in primary auditory cortex

Abstract

Event Abstract Back to Event Top-down influences on intensity coding in primary auditory cortex Liberty S. Hamilton1* and Shaowen Bao1 1 University of California, United States Both bottom-up (stimulus driven) and top-down (task-relevant) demands have been shown to influence cortical plasticity in adult rats. Previous research has shown that plasticity in A1 differs in rats trained to recognize sound loudness versus sound frequency, but it is not clear whether task demands may change neural coding strategies within one of these stimulus dimensions. We trained adult female Sprague Dawley rats on two different behavioral tasks using the same sound stimuli: (1) an intensity recognition task and (2) an intensity discrimination task. For (1), an absolute intensity recognition task, rats performed a two alternative forced choice task in which they listened to pure tone pip trains played at either 45 dB SPL or 60 dB SPL, and had to make a left nose poke when they heard a 45 dB at any frequency and the right for 60 dB at any frequency in order to receive a food reward. For (2), a relative intensity discrimination task, rats listened to trains of pure tone pips at either 45 dB or 60 dB, which, after a hold period, would then alternate between quiet and loud. The rat would receive a food reward by initiating a poke while the sounds alternated in level, indicating its ability to discriminate between the two sound levels. In both conditions, rats were trained using tone pips between 10.8 kHz and 21.2 kHz at either of the decibel levels, and training lasted approximately one month. Multiunit activity in response to pure tone pips from 1 kHz to 32 kHz and -5 dB SPL to 70 dB SPL was recorded from primary auditory cortex (A1) of trained rats and naïve controls under sodium pentobarbital anesthesia. From these data, we constructed classical receptive fields to determine the best frequency, frequency bandwidth, and best level of each recording site. We then calculated rate level functions (RLFs) for each recording site by calculating the average number of spikes at each intensity level, collapsed across frequencies. While we found no difference in frequency representation across groups, we found an increase in the number of nonmonotonic RLFs in the intensity recognition group compared to intensity discrimination and control rats. Both the fraction of nonmonotonic sites and the degree of nonmonotonicity for neurons increased in the recognition group compared to discrimination and controls, suggesting distinct mechanisms for encoding sound intensity in response to top-down behavioral demands. Such differences may be related to changes in the balance between excitatory and inhibitory synaptic activity in auditory cortex. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Hamilton LS and Bao S (2010). Top-down influences on intensity coding in primary auditory cortex. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00129 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: 01 Mar 2010; Published Online: 01 Mar 2010. * Correspondence: Liberty S Hamilton, University of California, Berkeley, United States, lhamilton@berkeley.edu 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 Liberty S Hamilton Shaowen Bao Google Liberty S Hamilton Shaowen Bao Google Scholar Liberty S Hamilton Shaowen Bao PubMed Liberty S Hamilton Shaowen Bao 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.