Anatomical arrangement of antennal-lobe tracts in the female moth
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- Institutt for psykologi 
Of all the senses, the sense of smell is the evolutionary oldest, and all organisms possess an organ that allows for detection and discrimination of chemosensory information. For a wide variety of animal species olfaction influences a diverse set of behaviors, as well as learning and memory. In this study, female heliothine moths were used as model animals to investigate the fiber tracts formed by second order projection neurons carrying olfactory information from the antennal-lobe, the primary olfactory processing center, to higher brain centers. This part of the insect olfactory pathway corresponds to the lateral olfactory tract of mammals consisting of axons projecting from the olfactory bulb to cortical regions in the temporal lobe. Previous studies on heliothine moths have described three main antennal-lobe tracts both in males and females. Since a fourth antennal-lobe tract was recently discovered in male moths, one of the main aims of the current study was to explore whether a corresponding tract is present in the female moth as well. Although the projection pattern of the classic antennallobe tracts has been previously mapped, there are still unanswered questions, especially regarding terminal regions of the lateral and the medial antennal-lobe tract. Data in the form of confocal images were obtained using anterograde mass staining of second order neurons originating in the antennal lobe. This labeling technique clearly visualized the antennal-lobe tracts. In some preparations, a double-labeling technique including two fluorescent dyes applied into different regions of the antennal lobe was used in order to investigate whether different categories of antennal-lobe glomeruli give rise to projection neurons targeting distinct regions of the lateral horn. Altogether, the successful stainings confirmed previous findings including visualization of the three classic antennal-lobe tracts. In addition, the transverse tract was identified in the female moth.