Chemical Neuroanatomy of the Fly's Movement Detection Pathway

Arizona Research Laboratories, Division of Neurobiology, University of Arizona, Tucson, Arizona 85721, USA.
The Journal of Comparative Neurology (Impact Factor: 3.23). 01/2004; 468(1):6-23. DOI: 10.1002/cne.10929
Source: PubMed


In Diptera, subsets of small retinotopic neurons provide a discrete channel from achromatic photoreceptors to large motion-sensitive neurons in the lobula complex. This pathway is distinguished by specific affinities of its neurons to antisera raised against glutamate, aspartate, gamma-aminobutyric acid (GABA), choline acetyltransferase (ChAT), and a N-methyl-D-aspartate type 1 receptor protein (NMDAR1). Large type 2 monopolar cells (L2) and type 1 amacrine cells, which in the external plexiform layer are postsynaptic to the achromatic photoreceptors R1-R6, express glutamate immunoreactivity as do directionally selective motion-sensitive tangential neurons of the lobula plate. L2 monopolar cells ending in the medulla are accompanied by terminals of a second efferent neuron T1, the dendrites of which match NMDAR1-immunoreactive profiles in the lamina. L2 and T1 endings visit ChAT and GABA-immunoreactive relays (transmedullary neurons) that terminate from the medulla in a special layer of the lobula containing the dendrites of directionally selective retinotopic T5 cells. T5 cells supply directionally selective wide-field neurons in the lobula plate. The present results suggest a circuit in which initial motion detection relies on interactions among amacrines and T1, and the subsequent convergence of T1 and L2 at transmedullary cell dendrites. Convergence of ChAT-immunoreactive and GABA-immunoreactive transmedullary neurons at T5 dendrites in the lobula, and the presence there of local GABA-immunoreactive interneurons, are suggested to provide excitatory and inhibitory elements for the computation of motion direction. A comparable immunocytological organization of aspartate- and glutamate-immunoreactive neurons in honeybees and cockroaches further suggests that neural arrangements providing directional motion vision in flies may have early evolutionary origins.

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Available from: Irina Sinakevitch, Sep 25, 2014
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    • "Various inputs may affect transmission by the interactions of clock, phototransduction and other proteins with BRP isoforms and the presence of both isoforms, equally contributing to the presynaptic element as in the NMJ (Matkovic et al., 2013), may stabilize synapse structure and provide more space for interactions with various proteins to modify synaptic transmission. In the case of feedback synapses they may inhibit activity of the retina photoreceptors during the night or increase their sensitivity (Sinakevitch and Strausfeld, 2004; Kolodziejczyk et al., 2008). They probably interact with less proteins than tetrad synapses and they seem to be structurally less complicated than tetrad synapses, at least by comparing EM images (Figures 1D,E) of both synapse classes. "
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    • "The GABAergic inhibitory IIIN further sharpens the direction selectivity by providing lateral inhibition between adjacent T5 neurons . ( See Sinakevitch & Strausfeld , 2004 , and Higgins , Douglass , & Strausfeld , 2004 , for a detailed description and numerical model of this neural circuit . ) The output of this neural circuit , via the T5 cells , constitutes the input in the well - studied lobula plate wide - field motion integration system , which computes the global motion direction from the local motion information supplied by T5 cells ( Single & Borst , 1998 ; Borst & Haag , 2002 ) . "
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