Odour representation in honeybee olfactory glomeruli shows slow temporal dynamics: an optical recording study using a voltage-sensitive dye

Stimulation with odours has been shown to elicit characteristic patterns of activated glomeruli in the antennal lobe (AL) of honeybees. In this study we show that these patterns are dynamic in a time window of 2-3 s after sti mulus onset. We measured changes in the averaged membrane potential of all cells in the glomerular neuropil by optical imaging of the voltage-sensitiv e dye RH795 using a slow scan CCD camera (3 frames/s). The four substances 1-hexanol, hexanal, citral and clove-oil as well as the binary mixtures hex anol+hexanal and hexanol+citral were used as stimuli (2 s stimulus duration ). We found that: (1) every odour elicited an odour-specific activity patte rn, and conversely every glomerulus had a characteristic odour response pro file; (2) some glomeruli had a tonic, some a phasic-tonic, and some a slow phasic response pattern; (3) the difference between the glomerular response patterns increased within 2 s of stimulus presentation, which suggests tha t odour representations became more characteristic over stimulus time; and (4) the responses to odorant mixtures were complex and glomerulus-dependent : some responses correspond to the sum of the compounds' responses, some to the response of one of the components. (C) 2000 Elsevier Science Ltd. All rights reserved.