γ-Aminobutyric acid receptor A-mediated inhibition in the honeybee's antennal lobe is necessary for the formation of configural olfactory percepts.

Complex odours often possess perceptual qualities that are distinct from their components. Previous studies in humans, rodents, and insects indicate that the perception of complex odour blends depends on the concentration of the components and the mixture's complexity. However, we know relatively little about the way that an odour mixture 'gestalt' is produced by the olfactory system. Here, using an assay for olfactory conditioning in the honeybee (Apis mellifera), we examine the role of γ-aminobutyric acid receptor A (GABA(A) )-ergic inhibition within the olfactory primary relay, the antennal lobe, in the formation of a unique odour percept for complex odours. We found that honeybees perceive odour mixtures as configural stimuli when the mixtures were of low concentration and when they were composed of more than two odorants. When GABA(A) receptors were disrupted using the antagonist, picrotoxin, injected directly into the antennal lobe, we observed that bees no longer perceived the mixture as a configural stimulus. Our results imply that synchronization of antennal lobe projection neurons mediated by GABA(A) receptors is the mechanism responsible for the formation of unique olfactory percepts for complex odours.