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Contrast Gain Control is Drift-Rate Dependent: An Informational Analysis

Hietanen, Markus; Crowder, Nathan; Ibbotson, Michael

Description

Neurons in the visual cortex code relative changes in illumination (contrast) and adapt their sensitivities to the visual scene by centering the steepest regions of their sigmoidal contrast response functions (CRFs: spike rate as a function of contrast) on the prevailing contrast. The influence of this contrast gain control has not been reported at nonoptimal drift rates. We calculated the Fisher information contained in the CRFs of halothane- anesthetized cats. Fisher information gives a...[Show more]

dc.contributor.authorHietanen, Markus
dc.contributor.authorCrowder, Nathan
dc.contributor.authorIbbotson, Michael
dc.date.accessioned2015-12-10T22:25:20Z
dc.identifier.issn0022-3077
dc.identifier.urihttp://hdl.handle.net/1885/53432
dc.description.abstractNeurons in the visual cortex code relative changes in illumination (contrast) and adapt their sensitivities to the visual scene by centering the steepest regions of their sigmoidal contrast response functions (CRFs: spike rate as a function of contrast) on the prevailing contrast. The influence of this contrast gain control has not been reported at nonoptimal drift rates. We calculated the Fisher information contained in the CRFs of halothane- anesthetized cats. Fisher information gives a measure of the accuracy of contrast representations based on the ratio of the square of the steepness of the CRF and the spike-rate dependency of the spiking variance. Variance increases with spike rate, so Fisher information is maximal where the CRF is steep and spike rates are low. Here, we show that the contrast at which the maximal Fisher information (CMFI) occurs for each adapting drift rate is at a fixed level above the adapting contrast. For adapting contrasts of 0 to 0.32 the relationship between CMFI and adapting contrast is well described by a straight line with a slope close to 1. The intercept of this line on the CMFI-axis is drift-rate dependent, although the slope is not. At high drift rates relative to each cell's peak the CMFI offset is higher than that for low drift rates. The results show that the contrast coding strategy in visual cortex maximizes accuracy for contrasts above the prevailing contrast in the environment for all drift rates. We argue that tuning the system for accuracy at contrasts above the prevailing value is optimal for viewing natural scenes.
dc.publisherAmerican Physiological Society
dc.sourceJournal of Neurophysiology
dc.subjectKeywords: animal cell; animal experiment; animal tissue; article; brain function; controlled study; illumination; neurotransmission; nonhuman; priority journal; visual cortex; visual stimulation; visual system; Animals; Cats; Contrast Sensitivity; Discrimination (P
dc.titleContrast Gain Control is Drift-Rate Dependent: An Informational Analysis
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume97
dc.date.issued2007
local.identifier.absfor110906 - Sensory Systems
local.identifier.ariespublicationu9204316xPUB273
local.type.statusPublished Version
local.contributor.affiliationHietanen, Markus, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationCrowder, Nathan, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationIbbotson, Michael, College of Medicine, Biology and Environment, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.startpage1078
local.bibliographicCitation.lastpage1087
local.identifier.doi10.1152/jn.00991.2006
dc.date.updated2015-12-09T09:23:20Z
local.identifier.scopusID2-s2.0-33846926722
CollectionsANU Research Publications

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