CiteULike: brembs's Hempel

Occasion setting in Drosophila at the flight simulator

J Wiener — 2008-07-30T12:58:12-00:00

Vol. 777.9 (2005)

Symmetry is in the eye of the beeholder: innate preference for bilateral symmetry in flower-naive bumblebees

I Rodriguez — 2008-07-30T12:57:22-00:00

Naturwissenschaften, Vol. 91, No. 8. (2004), 374-7.

Bilateral symmetry has been considered as an indicator of phenotypic and genotypic quality supporting innate preferences for highly symmetric partners. Insect pollinators preferentially visit flowers of a particular symmetry type, thus leading to the suggestion that they have innate preferences for symmetrical flowers or flower models. Here we show that flower-naive bumblebees (Bombus terrestris), with no experience of symmetric or asymmetric patterns and whose visual experience was accurately controlled, have innate preferences for bilateral symmetry. The presence of color cues did not influence the bees' original preference. Our results thus show that bilateral symmetry is innately preferred in the context of food search, a fact that supports the selection of symmetry in flower displays. Furthermore, such innate preferences indicate that the nervous system of naive animals may be primed to respond to relevant sensory cues in the environment.

Detection of bright and dim colours by honeybees

Hempel — 2008-07-30T12:55:13-00:00

J Exp Biol, Vol. 203, No. Pt 21. (2000), 3289-98.

Honeybees, Apis mellifera, were trained to detect coloured disks with either a strong or a weak intensity difference against the background. Green, blue, ultraviolet-reflecting white and grey papers were reciprocally combined as targets or backgrounds, providing strong chromatic and/or achromatic cues. The behavioural performance of the honeybees was always symmetrical for both reciprocal target/background combinations of a colour pair, thus showing that target detection is independent of whether the colour is presented as a background or as a target in combination with the other colour. Bright targets against dim backgrounds and vice versa were detected more reliably than dim target/background combinations. This result favours the general assumption that the detectability of a coloured stimulus increases with increasing intensity.

Discrimination of coloured patterns by honeybees through chromatic and achromatic cues

Hempel — 2008-07-30T12:55:13-00:00

J Comp Physiol A Neuroethol Sens Neural Behav Physiol, Vol. 188, No. 7. (2002), 503-12.

We investigated pattern discrimination by worker honeybees, Apis mellifera, focusing on the roles of spectral cues and the angular size of patterns. Free-flying bees were trained to discriminate concentric patterns in a Y-maze. The rewarded pattern could be composed of either a cyan and a yellow colour, which presented both different chromatic and achromatic L-receptor contrast, or an orange and a blue colour, which presented different chromatic cues, but the same L-receptor contrast. The non-rewarded alternative was either a single-coloured disc with the colour of the central disc or the surrounding ring of the pattern, a checkerboard pattern with non-resolvable squares, the reversed pattern, or the elements of the training pattern (disc or ring alone). Bees resolved and learned both colour elements in the rewarded patterns and their spatial properties. When the patterns subtended large visual angles, this discrimination used chromatic cues only. Patterns with yellow or orange central discs were generalised toward the yellow and orange colours, respectively. When the patterns subtended a visual angle close to the detection limit and L-receptor contrast was mediating discrimination, pattern perception was reduced: bees perceived only the pattern element with higher contrast.

Detection of coloured patterns by honeybees through chromatic and achromatic cues

Hempel — 2008-07-30T12:55:13-00:00

J Comp Physiol [A], Vol. 187, No. 3. (2001), 215-24.

We asked whether the detection range of two-coloured centre-surround patterns differs from that of single-coloured targets. Honeybees Apis mellifera were trained to distinguish between the presence and absence of a single-coloured disc or a coloured pattern at different visual angles. The patterns presented colours which were either different in chromatic and L-receptor contrasts to the background, equal in chromatic but different in L-receptor contrasts, or vice-versa. Patterns with colours presenting only chromatic contrast were also tested. Patterns with higher L-receptor contrast in its outer than in its inner element were better detected than patterns with a reversed L-contrast distribution. However, both were detected worse than single-coloured discs of the respective colours. When the L-receptor contrast was the same for both elements, the detection range of the two-coloured and single-coloured targets was the same. Patterns whose colours lacked L-receptor contrast were detected just as single-coloured targets of the same colours. These results demonstrate that both chromatic and L-receptor contrasts mediate the detection of coloured patterns and that particular distributions of L-receptor contrast within a target are better detected than others. This finding is consistent with the intervention of neurons with centre-surround receptive fields in the detection of coloured patterns.

Different parameters support generalization and discrimination learning in Drosophila at the flight simulator

B Brembs — 2008-07-30T12:53:41-00:00

Learn Mem, Vol. 13 (2006), 629-637.

We have used a genetically tractable model system, the fruit fly Drosophila melanogaster to study the interdependence between sensory processing and associative processing on learning performance. We investigated the influence of variations in the physical and predictive properties of color stimuli in several different operant-conditioning procedures on the subsequent learning performance. These procedures included context and stimulus generalization as well as color, compound, and conditional discrimination (colors and patterns). A surprisingly complex dependence of the learning performance on the colors physical and predictive properties emerged, which was clarified by taking into account the fly-subjective perception of the color stimuli. Based on estimates of the stimulis color and brightness values, we propose that the different tasks are supported by different parameters of the color stimuli; generalization occurs only if the chromaticity is sufficiently similar, whereas discrimination learning relies on brightness differences.