Configural olfactory learning in honeybees: Negative and positive patterning discrimination

In an appetitive context, honeybees (Apis mellifera) learn to associate odo rs with a reward of sucrose solution. If an odor is presented immediately b efore the sucrose, an elemental association is formed that enables the odor to release the proboscis extension response (PER. Olfactory conditioning o f PER was used to study whether, beyond elemental associations, honeybees a re able to process configural associations. Bees were trained in a positive and anegative patterning discrimination problem, in the first problem, sin gle odorants were nonreinforced whereas the compound was reinforced. In the second problem, single odorants were reinforced whereas the compound was n onreinforced. We studied whether bees can solve these problems and whether the ratio between the number of presentations of the reinforced stimuli and the number of presentations of the nonreinforced stimuli affects discrimin ation. Honey;bees differentiated reinforced and nonreinforced stimuli in po sitive and negative patterning discriminations. They thus can process confi gural associations. The variation of the ratio of reinforced to nonreinforc ed stimuli modulated the amount of differentiation. The assignment of singu lar codes to complex odor blends could be implemented at the neural level: When bees are stimulated with odor mixtures, the activation patterns evoked at the primary olfactory neuropile, the antennal lobe, may be combinations of the single odorant responses that are not necessarily fully additive.