title: Parallel processing in the honeybee olfactory pathway: structure, function, and evolution.
abstract: Animals face highly complex and dynamic olfactory stimuli in their natural environments, which require fast and reliable olfactory processing. Parallel processing is a common principle of sensory systems supporting this task, for example in visual and auditory systems, but its role in olfaction remained unclear. Studies in the honeybee focused on a dual olfactory pathway. Two sets of projection neurons connect glomeruli in two antennal-lobe hemilobes via lateral and medial tracts in opposite sequence with the mushroom bodies and lateral horn. Comparative studies suggest that this dual-tract circuit represents a unique adaptation in Hymenoptera. Imaging studies indicate that glomeruli in both hemilobes receive redundant sensory input. Recent simultaneous multi-unit recordings from projection neurons of both tracts revealed widely overlapping response profiles strongly indicating parallel olfactory processing. Whereas lateral-tract neurons respond fast with broad (generalistic) profiles, medial-tract neurons are odorant specific and respond slower. In analogy to "what-" and "where" subsystems in visual pathways, this suggests two parallel olfactory subsystems providing "what-" (quality) and "when" (temporal) information. Temporal response properties may support across-tract coincidence coding in higher centers. Parallel olfactory processing likely enhances perception of complex odorant mixtures to decode the diverse and dynamic olfactory world of a social insect.
authors.affiliation: Behavioral Physiology and Sociobiology (Zoology II), Biozentrum, University of Würzburg, Am Hubland, 97074, Würzburg, Germany, roessler@biozentrum.uni-wuerzburg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rössler
authors.forename: Martin F
authors.initials: MF
authors.lastname: Brill
mesh_terms: D000818:Animals; D001516:Bees; D005075:Biological Evolution; D009415:Nerve Net / Q000166:cytology / Q000502:physiology*; D009833:Olfactory Pathways / Q000033:anatomy & histology* / Q000502:physiology*; D012903:Smell / Q000502:physiology*