Honeybees (Apis mellifera) learn color discriminations via differential conditioning independent of long wavelength (green) photoreceptor modulation

Recent studies on colour discrimination suggest that experience is an important factor in how a visual system processes spectral signals. In insects it has been shown that differential conditioning is important for processing fine colour discriminations. However, the visual system of many insects, i...

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Bibliographic Details
Published in:PloS one 2012-11, Vol.7 (11), p.e48577-e48577
Main Authors: Reser, David H, Wijesekara Witharanage, Randika, Rosa, Marcello G P, Dyer, Adrian G
Format: Article
Language:English
Subjects:
Acetylcholine receptors
Animals
Apis mellifera
Bees
Bees - physiology
Behavior, Animal - physiology
Biology
Color
Color Perception - physiology
Color vision
Color Vision - physiology
Conditioning
Conditioning (Psychology) - physiology
Cues
Discrimination (Psychology) - physiology
Experiments
Insects
Irradiance
Learning
Light emitting diodes
Modulation
Organic light emitting diodes
Photic Stimulation
Photoreceptor Cells, Invertebrate - physiology
Photoreceptors
Physiology
Signal processing
Spectra
Stimuli
Studies
Vision
Visual aspects
Visual discrimination
Visual signals
Visual system
Wavelength
Wavelengths
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Summary:Recent studies on colour discrimination suggest that experience is an important factor in how a visual system processes spectral signals. In insects it has been shown that differential conditioning is important for processing fine colour discriminations. However, the visual system of many insects, including the honeybee, has a complex set of neural pathways, in which input from the long wavelength sensitive ('green') photoreceptor may be processed either as an independent achromatic signal or as part of a trichromatic opponent-colour system. Thus, a potential confound of colour learning in insects is the possibility that modulation of the 'green' photoreceptor could underlie observations. We tested honeybee vision using light emitting diodes centered on 414 and 424 nm wavelengths, which limit activation to the short-wavelength-sensitive ('UV') and medium-wavelength-sensitive ('blue') photoreceptors. The absolute irradiance spectra of stimuli was measured and modelled at both receptor and colour processing levels, and stimuli were then presented to the bees in a Y-maze at a large visual angle (26°), to ensure chromatic processing. Sixteen bees were trained over 50 trials, using either appetitive differential conditioning (N = 8), or aversive-appetitive differential conditioning (N = 8). In both cases the bees slowly learned to discriminate between the target and distractor with significantly better accuracy than would be expected by chance. Control experiments confirmed that changing stimulus intensity in transfers tests does not significantly affect bee performance, and it was possible to replicate previous findings that bees do not learn similar colour stimuli with absolute conditioning. Our data indicate that honeybee colour vision can be tuned to relatively small spectral differences, independent of 'green' photoreceptor contrast and brightness cues. We thus show that colour vision is at least partly experience dependent, and behavioural plasticity plays an important role in how bees exploit colour information.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0048577