The spatial representation of chemical structures in the antennal lobe of honeybees: steps towards the olfactory code
Silke Sachse, Angelika Rappert & C. Giovanni Galizia
Inst. Biologie - Neurobiologie, Fachbereich BioChemPharm, Freie Universität Berlin, D-14195 Berlin, Germany
Abstract
odors are represented by specific ensembles of activated glomeruli in a combinatorial manner within the olfacturoy bulb of vertebrates of the antennal lobe (AL) of insects. Here, we optically measured glomerular calcium activities in vivo in the honeybee Apis mellifera during olfactory stimulation with 36 pure chemicals differing systematically in carbon chain length (C-5-10) and functional group (aldehyde, ketone, alcohol, carboxylic acid and alkane). We show their glomerular representations in 38 morphologically identified glomeruli out of the honeybee's 160. We measured the molecular receptive range of identified glomeruli averaging up to 21 individuals. Of the 38 glomeruli measured, 23 show maximal activity in a specific range of chain length. Glomeruli preferentially responding to a functional group are also always broadly tuned to particular chain lengths. Furthermore, glomeruli with similar response spectra are often direct neighbours. The results allow conclusions about the interactions between olfactory receptors and odor molecules, and about the AL network.