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Organization and function of the central complex in the insect brain

The central complex is a group of interconnected neuropils in the center of the insect brain. It consists of the protocerebral bridge, the upper and lower divisions of the central body and a pair of posterior noduli. The most striking feature of this brain area is a highly modular arrangement of neural elements, forming series of layers and slices. To understand the functional role of this brain area, we have analyzed the neuroarchitecture of the lower division of the central body of the locust and of neurons providing the columnar organization of the central complex. Immunocytochemical studies showed that a large variety of neurotransmitters and neuropeptides is present in the central complex. We have provided detailed maps for the distribution of GABA, dopamine, serotonin, tyramine, octopamine, histamine, nitric oxide/cGMP, and of peptides related to allatostatins, CCAP, tachykinins, allatotropins, and SIFamide in distinct populations of central-complex neurons. Single cell recordings suggest that the central complex is involved in flight control and serves a role as navigational center for direction finding and spatial orientation. A network of polarization-sensitive neurons in the central complex suggests that it serves a role as an internal sky compass in the locust brain. A digital 3D atlas of the central complex and associated neuropils aids in further characterization of its functional role in spatial orientation.

Current anatomical/immunocytochemical projects are aimed at (i) analyzing visual signal processing in the central complex, in particular responses to small translating targets, looming and optomotor stimuli, (ii) investigating the role of motor activity on sensory signal processing, and (iii) establishing 3D reconstructions of all major cell types of the central complex.