ODOR CODING IS BILATERALLY SYMMETRICAL IN THE ANTENNAL LOBES OF HONEYBEES (APIS-MELLIFERA)

The primary olfactory neuropil, the antennal lobe (AL) in insects, is organized in glomeruli. Glomerular activity patterns are believed to r epresent the across-fibre pattern of the olfactory code. These pattern s depend on an organized innervation from the afferent receptor cells, and interconnections of local interneurons. It is unclear how the com plex organization of the AL is achieved ontogenetically. In this study , we measured the functional activity patterns elicited by stimulation with odours in the right and the left AL of the same honeybee (Apis m ellifera) using optical imaging of the calcium-sensitive dye calcium g reen. We show here that these patterns are bilaterally symmetrical (n = 25 bees). This symmetry holds true for all odours tested, irrespecti ve of their role as pheromones or as environmental odours, or whether they were pure substances or complex blends (n = 13 odours). Therefore , we exclude that activity dependent mechanisms local to one AL determ ine the functional glomerular activity. This identity is genetically p redetermined. Alternatively, if activity dependent processes are invol ved, bilateral connections would have to shape symmetry, or, temporal constraints could lead to identical patterns on both sides due to thei r common history of odour exposure.