Overview of the central olfactory pathway in a malacostracan crustacean, the crayfish (modified from []). The olfactory receptor axons (orange) are the primary sensory input and innervate the cap of the olfactory glomeruli. Local interneurons (purple) in cell cluster (9) and dorsal giant neurons (serotonergic, turquoise) in cell cluster (11) are associated with the olfactory and the accessory lobe. The olfactory glomeruli are compartmentalized into the cap, subcap, and base regions (see Figure10 for details). Local interneurons innervate specific compartments of the olfactory glomeruli and were classified as e.g. rim or core interneurons. The dorsal giant neuron (DGN) innervates both the olfactory glomeruli and the accessory lobe. The accessory lobe also shows responses to visual and mechanosensory stimuli. From the olfactory lobe and accessory lobe, processed information is relayed to the secondary computational centers in the lateral protocerebrum, the medulla terminalis and the hemiellipsoid body via the projection neuron tract (blue), that also provides contralateral connections. In the lateral protocerebrum, this input interacts with the intrinsic lateral protocerebral interneurons, often termed “globuli cells”. Projection neurons associated with the accessory lobe target the hemiellipsoid body whereas those asscociated with the olfactory glomeruli mostly target the medulla terminalis. The lateral protocerebrums also receives indirect mechanosensory and visual input in addition to chemosensory information and hence is a multimodal center.