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Neural basis of polarization vision in the brain of desert locusts

Behavioral experiments in honeybees, ants, and other insects have shown that the polarization pattern of the blue sky serves an important role in insect compass navigation and spatial orientation. We investigate the neural mechanisms underlying polarized skylight navigation in the desert locust Schistocerca gregaria. In S. gregaria, as in other insects, a small dorsal rim area of the compound eye is highly specialized for the detection of polarized light. We have characterized behavioral responses of locusts to polarized light, analyzed the properties of dorsal rim photoreceptors, and have identified neural pathways in the locust brain that are involved in processing of polarized light information. Polarization-sensitive (POL) interneurons were characterized physiologically in the medulla, the anterior optic tubercle of the brain, the central complex of the central brain, and in the ventral nerve cord. Most polarization-sensitive interneurons show polarization opponency, i.e. E-vectors leading to maximal excitation are perpendicular to E-vectors causing maximal inhibition.

Current projects analyze (i) receptive-field properties of polarization-sensitive photoreceptors and brain interneurons, (ii) mechanisms underlying the topographical representation of celestial E-vectors in the central complex, and (iii) state-dependent changes in polarization sensitivity in the central complex.