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Contrast adaptation and interocular transfer in cortical cells: a re-analysis & a two-stage gain-control model of binocular combination

Georgeson, Mark A. and Sengpiel, Frank 2021. Contrast adaptation and interocular transfer in cortical cells: a re-analysis & a two-stage gain-control model of binocular combination. Vision Research 185 , pp. 29-49. 10.1016/j.visres.2021.03.004
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Abstract

How do V1 cells respond to, adapt to, and combine signals from the two eyes? We tested a simple functional model that has monocular and binocular stages of divisive contrast gain control (CGC) that sit before, and after, binocular summation respectively. Interocular suppression (IOS) was another potential influence on contrast gain. Howarth, Vorobyov & Sengpiel (2009, Cerebral Cortex, 19, 1835–1843) studied contrast adaptation and interocular transfer in cat V1 cells. In our re-analysis we found that ocular dominance (OD) and contrast adaptation at a fixed test contrast were well described by a re-scaling of the unadapted orientation tuning curve – a simple change in response gain. We compared six variants of the basic model, and one model fitted the gain data notably better than the others did. When the dominant eye was tested, adaptation reduced cell response gain more when that eye was adapted than when the other eye was adapted. But when the non-dominant eye was tested, adapting either eye gave about the same reduction in overall gain, and there was an interaction between OD and adapting eye that was well described by the best-fitting model. Two key features of this model are that signals driving IOS arise 'early', before attenuation due to OD, while suppressive CGC signals are 'late' and so affected by OD. We show that late CGC confers a functional advantage: it yields partial compensation for OD, which should reduce ocular imbalance at the input to binocular summation, and improve the cell's sensitivity to variation in stereo disparity.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Publisher: Elsevier
ISSN: 0042-6989
Date of First Compliant Deposit: 26 March 2021
Date of Acceptance: 9 March 2021
Last Modified: 17 Oct 2021 18:50
URI: http://orca.cardiff.ac.uk/id/eprint/140132

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