Abstract
The accuracy of the neural code depends on the relative embedding of signal and noise in the activity of neural populations. Despite a wealth of theoretical work on population codes, there are few empirical characterisations of the high-dimensional signal and noise subspaces. We studied the geometry of population codes in the rat auditory cortex across brain states along the activation-inactivation continuum, using sounds varying in difference and mean level across the ears. As the cortex becomes more activated, single-hemisphere populations go from preferring contralateral loud sounds to a symmetric preference across lateralisations and intensities, gain-modulation effectively disappears, and the signal and noise subspaces become approximately orthogonal to each other and to the direction corresponding to global activity modulations. Level-invariant decoding of sound lateralisation also becomes possible in the active state. Our results provide an empirical foundation for the geometry and state-dependence of cortical population codes.
Article and author information
Author details
Funding
Fundacao Bial (389/14)
- Dmitry Kobak
EU FP7 grant (ICT-2011-9-600925)
- Alfonso Renart
German Ministry of Education and Research (FKZ 01GQ1601)
- Dmitry Kobak
HFSP postdoctoral fellowship (LT 000442/2012)
- Jose L Pardo-Vazquez
Fundacao para a Ciencia e a Tecnologia
- Mafalda Valente
Champalimaud Foundation
- Christian K Machens
- Alfonso Renart
Simons Collaboration on the Global Brain (543009)
- Christian K Machens
National Institutes of Health (U01 NS094288)
- Christian K Machens
Marie Curie Career Integration Grant (PCIG11-GA-2012-322339)
- Alfonso Renart
HFSP Young Investigator Award (RGY0089)
- Alfonso Renart
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All procedures were carried out in accordance with European Union Directive 86/609/EEC and approved by Direçao-Geral de Veterinaria.
Reviewing Editor
- Emilio Salinas, Wake Forest School of Medicine, United States
Publication history
- Received: December 19, 2018
- Accepted: April 7, 2019
- Accepted Manuscript published: April 10, 2019 (version 1)
- Version of Record published: April 30, 2019 (version 2)
Copyright
© 2019, Kobak et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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