University of Oulu

Irina I. Ignatova, Andrew S. French, and Roman V. Frolov. Effects of phase correlations in naturalistic stimuli on quantitative information coding by fly photoreceptors. Journal of Neurophysiology 2018 119:6, 2276-2290.

Effects of phase correlations in naturalistic stimuli on quantitative information coding by fly photoreceptors

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Author: Ignatova, Irina I.1; French, Andrew S.2; Frolov, Roman V.1
Organizations: 1Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
2Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 2.7 MB)
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Language: English
Published: American Physiological Society, 2018
Publish Date: 2019-06-15


Natural visual scenes are rarely random. Instead, intensity and wavelength change slowly in time and space over many regions of the scene, so that neighboring temporal and spatial visual inputs are more correlated and contain less information than truly random signals. It has been suggested that sensory optimization to match these higher order correlations (HOC) occurs at the earliest visual stages, and that photoreceptors can process temporal natural signals more efficiently than random signals. We tested this early-stage hypothesis by comparing the information content of Calliphora vicina photoreceptor responses to naturalistic inputs before and after removing HOC by randomizing phase. Forty different, 60-s long, naturalistic sequences (NS) were used, together with randomized-phase versions of the same sequences to give pink noise (PN) so that each input pair had identical means, variances, mean contrasts, and power spectra. We measured the information content of inputs and membrane potential responses by three different methods: coherence, mutual information, and compression entropy. We also used entropy and phase statistics of each pair as measures of HOC. Responses to randomized signals generally had higher gain, signal-to-noise ratio, and information rates than responses to NS. Information rate increased with a strong, positive, linear correlation to phase randomization within sequence pairs. This was confirmed by varying the degree of phase randomization. Our data indicate that individual photoreceptors encode input information by Weber’s law, with HOC within natural sequences reducing information transfer by decreasing the number of local contrast events that exceed the noise-imposed threshold.

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Series: Journal of neurophysiology
ISSN: 0022-3077
ISSN-E: 1522-1598
ISSN-L: 0022-3077
Volume: 119
Issue: 6
Pages: 2276 - 2290
DOI: 10.1152/jn.00017.2018
Type of Publication: A1 Journal article – refereed
Field of Science: 1184 Genetics, developmental biology, physiology
3112 Neurosciences
Funding: This research was supported by a Natural Sciences and Engineering Research Council of Canada grant RGPIN 03712 to A. S. French.
Copyright information: Copyright © 2018 the American Physiological Society.