期刊
JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY
卷 200, 期 3, 页码 197-207出版社
SPRINGER
DOI: 10.1007/s00359-013-0878-7
关键词
Spectral sensitivity; Single cone; Double cone; Chromatic mechanisms; Achromatic mechanisms
资金
- Royal Physiographic Society in Lund
- Swedish Research Council [621-2009-5683]
- Knut and Alice Wallenberg Foundation
- Royal Swedish Academy of Sciences
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 (3.4A degrees) 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.
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