Gabbiani, Fabrizio and Mo, Chun-Hui and Laurent, Gilles (2001) Invariance of Angular Threshold Computation in a Wide-Field Looming-Sensitive Neuron. Journal of Neuroscience, 21 (1). p. 314. ISSN 0270-6474. http://resolver.caltech.edu/CaltechAUTHORS:20130816-103143220
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The lobula giant motion detector (LGMD) is a wide-field bilateral visual interneuron in North American locusts that acts as an angular threshold detector during the approach of a solid square along a trajectory perpendicular to the long axis of the animal (Gabbiani et al., 1999a). We investigated the dependence of this angular threshold computation on several stimulus parameters that alter the spatial and temporal activation patterns of inputs onto the dendritic tree of the LGMD, across three locust species. The same angular threshold computation was implemented by LGMD in all three species. The angular threshold computation was invariant to changes in target shape (from solid squares to solid discs) and to changes in target texture (checkerboard and concentric patterns). Finally, the angular threshold computation did not depend on object approach angle, over at least 135° in the horizontal plane. A two-dimensional model of the responses of the LGMD based on linear summation of motion-related excitatory and size-dependent inhibitory inputs successfully reproduced the experimental results for squares and discs approaching perpendicular to the long axis of the animal. Linear summation, however, was unable to account for invariance to object texture or approach angle. These results indicate that LGMD is a reliable neuron with which to study the biophysical mechanisms underlying the generation of complex but invariant visual responses by dendritic integration. They also suggest that invariance arises in part from non-linear integration of excitatory inputs within the dendritic tree of the LGMD.
|Additional Information:||Copyright © 2001 Society for Neuroscience. Received April 10, 2000; revised Oct. 10, 2000; accepted Oct. 18, 2000. This work was supported by the German American Academic Council, by a National Institute on Deafness and Other Communication Disorders (National Institutes of Health) grant to G.L., by a National Science Foundation grant to C.K., and by the Sloan Center for Theoretical Neuroscience at Caltech. Experiments and data analysis were carried out by F.G. and C.M.; F.G. and G.L. co-wrote the paper. We thank Dr. A. Hassanali (ICIPE) and Dr. H. Krapp (University of Bielefeld) for kindly furnishing L. migratoria and S. gregaria specimens, as well as Dr. D. Sheinberg for help in setting up the data acquisition system. F.G. and C.M. thank Dr. C. Koch for many discussions and his encouragement over the course of this project.|
|Group:||Koch Laboratory, KLAB|
|Subject Keywords:||invariant responses; looming; locust; LGMD; DCMD; collision avoidance|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||KLAB Import|
|Deposited On:||11 Jan 2008 22:47|
|Last Modified:||20 Nov 2015 01:12|
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