State-dependent geometry of population activity in rat auditory cortex
- Champalimaud Centre for the Unknown, Portugal
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.
Data availability
The full Matlab code for the analysis is located at https://github.com/dkobak/a1geometry. We made the spike count data (spike counts for each neuron for each stimulus presentation from −50 ms to 150 ms in 50 ms bins) available in the same repository. This allows most of our figures to be reproduced. The complete dataset that was collected, including spike time data not analysed here, is available upon reasonable request to the corresponding author.
Article and author information
Author details
Jose L Pardo-Vazquez
Christian K Machens
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.
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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State-dependent geometry of population activity in rat auditory cortex
eLife 8:e44526.
https://doi.org/10.7554/eLife.44526
