Neural Organization of Olfactory Signal Pathways in a Small Model Brain

Abstract

The chemical sense is regarded as the oldest sense, and all organisms have evolved a mechanism in order to detect molecules in the environment. Among many other creatures, the moth depends fundamentally on chemical communication for survival. Besides, this insect group possesses an easy accessible olfactory system that shares striking similarities with that of vertebrates. In the project presented here, the moth brain is used as a model for studying the olfactory system; more precisely, the parallel olfactory pathways connec ing the primary olfactory center with higher regions of the brain have been investigated. By performing retrograde staining of antennal-lobe projection neurons, five antennocerebral tracts were identified. Stained projectionneuron somata, which are located in the antennal lobe, were found in all three cell clusters: the lateral, the medial and the anterior cell cluster. The stained somata in the lateral cell cluster consisted of two distinctly located groups. The retrograde staining of projection neurons also visualized the glomerular labeling pattern in the antennal lobe. This labeling pattern included a small group of glomeruli that were strongly innervated by fibers from the dorsomedial antennocerebral tract.