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

BACKGROUND: 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. METHODOLOGY/PRINCIPAL FINDINGS: 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.
CONCLUSION: 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.