Abstract
Summary Olfaction plays an essential role in animal behaviors including courtship, avoidance, and food searching as well as higher functions such as learning and memory. In Drosophila, olfactory receptor neurons (ORNs) sense and deliver specific odorant stimuli to specific glomeruli where their axons contact with dendrites of projection neurons (PNs) forming a stereotyped spatial map in the antennal lobe. To understand how this olfactory map is translated in the higher brain centers to ultimately elicit corresponding behaviors, I address the olfactory representation in the mushroom body (MB), an olfactory learning center. Using genetic mosaic MARCM system, I mapped spatial distributions of 128 individual PNs in the MB calyx. We have recently shown that KC dendrites in the calyx are segregated into 17 domains as a result of lineage development and sequential birth. PN/KC connectivity likelihood assignment indicates that with only few exceptions each PN connects to neurons of only one of the five KC classes (□,□□'/□'□□pioneer □/□□ early □/□ and late□□/□□neurons□. Colocalization analysis also shows that each PN gives different numbers of terminal boutons to the four vertical clonal divisions in a stereotypical manner. These data suggest that neural coding of olfactory stimuli in the antennal lobe is transformed and decoded in the MB by the selective connectivity between each PN and specific types of KCs.