title: Coarse topographic organization of pheromone-sensitive afferents from different antennal surfaces in the American cockroach.
abstract: In contrast to visual, auditory, taste, and mechanosensory neuropils, in which sensory afferents are topographically organized on the basis of their peripheral soma locations, axons of cognate sensory neurons from different locations of the olfactory sense organ converge onto a small spherical neuropil (glomerulus) in the first-order olfactory center. In the cockroach Periplaneta americana, sex pheromone-sensitive afferents with somata in the antero-dorsal and postero-ventral surfaces of a long whip-like antenna are biased toward the anterior and posterior regions of a macroglomerulus, respectively. In each region, afferents with somata in the more proximal antenna project to more proximal region, relative to the axonal entry points. However, precise topography of afferents in the macroglomerulus has remained unknown. Using single and multiple neuronal stainings, we showed that afferents arising from anterior, dorsal, ventral and posterior surfaces of the proximal regions of an antenna were biased progressively from the anterior to posterior region of the macroglomerulus, reflecting chiasmatic axonal re-arrangements that occur immediately before entering the antennal lobe. Morphologies of individual afferents originating from the proximal antenna matched results of mass neuronal stainings, but their three-dimensional origins in the antenna were hardly predictable on the basis of the projection patterns. Such projection biases made by neuronal populations differ from strict somatotopic projections of antennal mechanosensory neurons in the same species, suggesting a unique sensory mechanism to process information about odor location and direction on a single antenna.
authors: Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan. Electronic address: nishino@es.hokudai.ac.jp.
authors: Hiroshi
authors: H
authors: Nishino
authors: Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan.
authors: Hidehiro
authors: H
authors: Watanabe
authors: Maxnet Co., Ltd., Tokyo 164-0001, Japan.
authors: Itsuro
authors: I
authors: Kamimura
authors: Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan.
authors: Fumio
authors: F
authors: Yokohari
authors: Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Makoto
authors: M
authors: Mizunami
mesh_terms: D000818:Animals; D057506:Arthropod Antennae / Q000502:physiology*; D008297:Male; D019581:Neuropil / Q000502:physiology; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D010526:Periplaneta / Q000502:physiology*; D010675:Pheromones / Q000502:physiology*
chemical_list: D010675:Pheromones
keywords: Antenna; Glomerulus; Insects; Olfactory afferents; Sex pheromone; Topographic map