The lAL PNs can be grouped into five classes based on neuron morphology.

<p>Single PNs labeled by ts-MARCM with <i>nSyb-GAL4</i> (magenta). Their LN sibs are not shown. Brains were co-stained with nc82 mAb (blue). Based on their morphology, the lAL PNs are grouped into classical monoglomerular PN (mPN), unilateral PN (unPN), bilateral PN (biPN), antennal mechanosensory and motor center (AMMC) PN, or suboesophageal ganglion (SOG) PN. The dendrites of each mPN innervate a single glomerulus in AL and its axon project to mushroom body (MB) and lateral horn (LH) through inner antennocerebral tract (iACT). The unPNs and biPNs also have proximal innervations in AL, but unPNs innervate ipsilateral AL only and biPNs innervate both ipsilateral and contralateral ALs. Different from mPNs that project axons exclusively to MB and LH, unPNs and biPNs have distal projections targeting many other brain regions, often not through iACT. The AMMC and SOG PNs do not innervate AL but instead innervate AMMC and SOG, respectively. The brain regions innervated by each type of the lAL neurons are marked (arrows). The 12 types of mPN are named according to the glomeruli they innervate in AL, and their AL and lateral horn (LH) innervation are shown separately. Scale bar: 40 µm. Except for the AL region of mPNs, the background clones in these images were masked as described in Materials and Methods. AL, antennal lobe; cAL, contralateral AL; PLP, posteriorlateral protocerebrum; PVLP, posterior ventrolateral protocerebrum; cPVLP, contralateral posterior ventrolateral protocerebrum; SOG, suboesophageal ganglion; IB, inferior bridge; Ca, mushroom body calyx; LH, lateral horn; AMMC, antennal mechanosensory and motor center; cAMMC, contralateral antennal mechanosensory and motor center; IVLP, inferior ventrolateral protocerebrum; cIVLP, contralateral inferior ventrolateral protocerebrum; SMP, superior medial protocerebrum; CRE, crepine.