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  • 1
    Publication Date: 2013-08-09
    Description: The extraction of directional motion information from changing retinal images is one of the earliest and most important processing steps in any visual system. In the fly optic lobe, two parallel processing streams have been anatomically described, leading from two first-order interneurons, L1 and L2, via T4 and T5 cells onto large, wide-field motion-sensitive interneurons of the lobula plate. Therefore, T4 and T5 cells are thought to have a pivotal role in motion processing; however, owing to their small size, it is difficult to obtain electrical recordings of T4 and T5 cells, leaving their visual response properties largely unknown. We circumvent this problem by means of optical recording from these cells in Drosophila, using the genetically encoded calcium indicator GCaMP5 (ref. 2). Here we find that specific subpopulations of T4 and T5 cells are directionally tuned to one of the four cardinal directions; that is, front-to-back, back-to-front, upwards and downwards. Depending on their preferred direction, T4 and T5 cells terminate in specific sublayers of the lobula plate. T4 and T5 functionally segregate with respect to contrast polarity: whereas T4 cells selectively respond to moving brightness increments (ON edges), T5 cells only respond to moving brightness decrements (OFF edges). When the output from T4 or T5 cells is blocked, the responses of postsynaptic lobula plate neurons to moving ON (T4 block) or OFF edges (T5 block) are selectively compromised. The same effects are seen in turning responses of tethered walking flies. Thus, starting with L1 and L2, the visual input is split into separate ON and OFF pathways, and motion along all four cardinal directions is computed separately within each pathway. The output of these eight different motion detectors is then sorted such that ON (T4) and OFF (T5) motion detectors with the same directional tuning converge in the same layer of the lobula plate, jointly providing the input to downstream circuits and motion-driven behaviours.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maisak, Matthew S -- Haag, Juergen -- Ammer, Georg -- Serbe, Etienne -- Meier, Matthias -- Leonhardt, Aljoscha -- Schilling, Tabea -- Bahl, Armin -- Rubin, Gerald M -- Nern, Aljoscha -- Dickson, Barry J -- Reiff, Dierk F -- Hopp, Elisabeth -- Borst, Alexander -- England -- Nature. 2013 Aug 8;500(7461):212-6. doi: 10.1038/nature12320.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute of Neurobiology, 82152 Martinsried, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23925246" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Behavior, Animal/physiology ; Drosophila/cytology/*physiology ; Interneurons/physiology ; Locomotion/physiology ; Motion Perception/*physiology ; Neurons/physiology ; Signal Transduction ; Visual Pathways/cytology/*physiology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2010-11-12
    Description: Motion vision is a major function of all visual systems, yet the underlying neural mechanisms and circuits are still elusive. In the lamina, the first optic neuropile of Drosophila melanogaster, photoreceptor signals split into five parallel pathways, L1-L5. Here we examine how these pathways contribute to visual motion detection by combining genetic block and reconstitution of neural activity in different lamina cell types with whole-cell recordings from downstream motion-sensitive neurons. We find reduced responses to moving gratings if L1 or L2 is blocked; however, reconstitution of photoreceptor input to only L1 or L2 results in wild-type responses. Thus, the first experiment indicates the necessity of both pathways, whereas the second indicates sufficiency of each single pathway. This contradiction can be explained by electrical coupling between L1 and L2, allowing for activation of both pathways even when only one of them receives photoreceptor input. A fundamental difference between the L1 pathway and the L2 pathway is uncovered when blocking L1 or L2 output while presenting moving edges of positive (ON) or negative (OFF) contrast polarity: blocking L1 eliminates the response to moving ON edges, whereas blocking L2 eliminates the response to moving OFF edges. Thus, similar to the segregation of photoreceptor signals in ON and OFF bipolar cell pathways in the vertebrate retina, photoreceptor signals segregate into ON-L1 and OFF-L2 channels in the lamina of Drosophila.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Joesch, Maximilian -- Schnell, Bettina -- Raghu, Shamprasad Varija -- Reiff, Dierk F -- Borst, Alexander -- England -- Nature. 2010 Nov 11;468(7321):300-4. doi: 10.1038/nature09545.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉MPI for Neurobiology, Department of Systems and Computational Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21068841" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium Signaling/radiation effects ; Drosophila melanogaster/cytology/metabolism/*physiology/radiation effects ; Female ; Gap Junctions/metabolism/radiation effects ; Light ; Models, Neurological ; *Motion ; Motion Perception/*physiology/radiation effects ; Optic Lobe, Nonmammalian/cytology/physiology/radiation effects ; Photoreceptor Cells, Invertebrate/metabolism/radiation effects ; Vision, Ocular/*physiology/radiation effects ; Visual Pathways/cytology/*physiology/radiation effects
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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