Anatomical organization of the central olfactory pathways : mapping the transverse tract in the moth brain
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- Institutt for psykologi 
The sense of smell is regarded as the oldest and best conserved of all the senses. The fact that every organism has established the ability to detect chemicals in the external environment implies the importance of chemosensation. Due to their well-developed sense of smell and easily accessible nervous system, moths have served as suitable model organisms for researchers exploring general principles underlying odor information processing. Like in other insects, moths perceive odorants via olfactory sensory neurons located mainly on the antennae. The chemical stimuli, including plant odorants and pheromones, initiate different instinctive behaviors associated with mating and foraging. In this study, one distinctive level of the olfactory pathway that connects the primary olfactory center, the antennal lobe, to higher regions in the moth brain, was anatomically characterized. This path is formed by several parallel antennal-lobe tracts, including one newly discovered fiber bundle named the transverse tract. The last mentioned tract was especially explored in the study presented here. Generally, the neural pathway formed by the antennal-lobe tracts corresponds to the human olfactory tract conveying olfactory information from the olfactory bulb to cortical areas. The data in this study was obtained by performing anterograde mass labeling combined with confocal microscopy. Successfully stained preparations visualized the tree classical antennal-lobe tracts as well as the transverse tract.