Thresholds and noise limitations of colour vision in dim light

Research output: Contribution to journalReview article

Abstract

Colour discrimination is based on opponent photoreceptor interactions, and limited by receptor noise. In dim light, photon shot noise impairs colour vision, and in vertebrates, the absolute threshold of colour vision is set by dark noise in cones. Nocturnal insects (e.g. moths and nocturnal bees) and vertebrates lacking rods (geckos) have adaptations to reduce receptor noise and use chromatic vision even in very dim light. In contrast, vertebrates with duplex retinae use colour-blind rod vision when noisy cone signals become unreliable, and their transition from cone- to rod-based vision is marked by the Purkinje shift. Rod–cone interactions have not been shown to improve colour vision in dim light, but may contribute to colour vision in mesopic light intensities. Frogs and toads that have two types of rods use opponent signals from these rods to control phototaxis even at their visual threshold. However, for tasks such as prey or mate choice, their colour discrimination abilities fail at brighter light intensities, similar to other vertebrates, probably limited by the dark noise in cones.

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Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Zoology

Keywords

  • Colour vision, Purkinje shift, Visual ecology, Visual threshold
Original languageEnglish
Article number20160065
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Volume372
Issue number1717
Publication statusPublished - 2017 Apr 5
Publication categoryResearch
Peer-reviewedYes