The contribution of single and double cones to spectral sensitivity in budgerigars during changing light conditions.
Author
Summary, in English
Bird colour vision is mediated by single cones, while double cones and rods mediate luminance vision in bright and dim light, respectively. In daylight conditions, birds use colour vision to discriminate large objects such as fruit and plumage patches, and luminance vision to detect fine spatial detail and motion. However, decreasing light intensity favours achromatic mechanisms and eventually, in dim light, luminance vision outperforms colour vision in all visual tasks. We have used behavioural tests in budgerigars (Melopsittacus undulatus) to investigate how single cones, double cones and rods contribute to spectral sensitivity for large (3.4°) static monochromatic stimuli at light intensities ranging from 0.08 to 63.5 cd/m(2). We found no influences of rods at any intensity level. Single cones dominate the spectral sensitivity function at intensities above 1.1 cd/m(2), as predicted by a receptor noise-limited colour discrimination model. Below 1.1 cd/m(2), spectral sensitivity is lower than expected at all wavelengths except 575 nm, which corresponds to double cone function. We suggest that luminance vision mediated by double cones restores visual sensitivity when single cone sensitivity quickly decreases at light intensities close to the absolute threshold of colour vision.
Publishing year
2014
Language
English
Pages
197-207
Publication/Series
Journal of Comparative Physiology A
Volume
200
Issue
3
Document type
Journal article
Publisher
Springer
Topic
- Zoology
- Philosophy
Keywords
- Single cone
- Spectral sensitivity
- Chromatic mechanisms
- Double cone
- Achromatic mechanisms
Status
Published
Research group
- Lund Vision Group
ISBN/ISSN/Other
- ISSN: 1432-1351