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David Courtnay Marr (January 19, 1945 - November 17, 1980) was a British neuroscientist and psychologist. Marr integrated results from psychology, artificial intelligence, and neurophysiology into new models of visual processing. His work was very influential in Computational Neuroscience and led to a resurgence of interest in the discipline.
Born in Woodford, Essex, and educated at Rugby School; he was admitted at Trinity College, Cambridge on 1 October 1963 (having been awarded the Lees Knowles Rugby Exhibition). He was awarded the Coutts Trotter Scholarship in 1966 and obtained his BA in mathematics the same year and got his Ph.D. in physiology under Professor G.S. Brindley in 1972. His interest turned from general brain theory to visual processing. His doctoral dissertation was submitted in 1969 and described his model of the function of the cerebellum based mainly on anatomical and physiological data garnered from a book by J.C. Eccles. A similar model was later independently proposed by James S. Albus. Subsequently he worked at the Massachusetts Institute of Technology, where he took on a faculty appointment in the Department of Psychology in 1977 and was subsequently made a tenured full professor in 1980. Marr proposed that understanding the brain requires an understanding of the problems it faces and the solutions it finds. He emphasized the need to avoid general theoretical debates and instead focus on understanding specific problems.
Marr died of leukemia in Cambridge, Massachusetts. Marr's findings are collected in the book Vision: A computational investigation into the human representation and processing of visual information (ISBN 0-7167-1567-8), which was published after his death and re-issued in 2010 by The MIT Press (see References). He was married to Lucia M. Vaina of Boston University's Department of Biomedical Engineering and Neurology. The Marr Prize, one of the most prestigious awards in computer vision, is named in his honor.
Levels of analysis
Marr treated vision as an information processing system. He put forth (in concert with Tomaso Poggio) the idea that one must understand information processing systems at three distinct, complementary levels of analysis. This idea is known in cognitive science as Marr's Tri-Level Hypothesis: 
- computational level: what does the system do (e.g.: what problems does it solve or overcome) and, equally importantly, why does it do these things
- algorithmic/representational level: how does the system do what it does, specifically, what representations does it use and what processes does it employ to build and manipulate the representations
- implementational level: how is the system physically realized (in the case of biological vision, what neural structures and neuronal activities implement the visual system)
Stages of vision
Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include
- a primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression.
- a 2.5D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth.
- a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.
Francis Crick noted that this insight although seminal, has been somewhat modified.
2.5D sketch is related to stereopsis, optic flow, and motion parallax. The 2.5D sketch represents that in reality we do not see all of our surroundings but construct the viewer-centered three dimensional view of our environment. 2.5D Sketch is a paraline drawing and often referred to by its generic term "axonometric" or "isometric" drawing and are often used by modern architects and designers.
- Marr, D. (1982) Vision: a Computational Investigation into the Human Representation and Processing of Visual Information, San Francisco: W.H. Freeman.ISBN 0-7167-1567-8,
- (1969) "A theory of cerebellar cortex." J. Physiol., 202:437-470.
- (1970) "A theory for cerebral neocortex." Proceedings of the Royal Society of London B, 176:161-234.
- (1971) "Simple memory: a theory for archicortex." Phil. Trans. Royal Soc. London, 262:23-81.
- (1974) "The computation of lightness by the primate retina." Vision Research, 14:1377-1388.
- (1975) "Approaches to biological information processing." Science, 190:875-876.
- (1976) "Early processing of visual information." Phil. Trans. R. Soc. Lond. B, 275:483-524.
- (1976) "Cooperative computation of stereo disparity." Science, 194:283-287. (with Tomaso Poggio)
- (1976, March) "Artificial intelligence: A personal view." Technical Report AIM 355, MIT AI Laboratory, Cambridge, MA.
- (1977) "Artificial intelligence: A personal view." Artificial Intelligence 9(1), 37–48.
- (1977) "From understanding computation to understanding neural circuitry." Neurosciences Res. Prog. Bull., 15:470-488. (with Tomaso Poggio)
- (1978) "Representation and recognition of the spatial organization of three dimensional shapes." Proceedings of the Royal Society of London B, 200:269-294. (with H. K. Nishihara)
- (1979) "A computational theory of human stereo vision." Proceedings of the Royal Society of London B, 204:301-328. (with Tomaso Poggio)
- (1980) "Theory of edge detection." Proc. R. Soc. Lond. B, 207:187-217. (with E. Hildreth)
- (1981) "Artificial intelligence: a personal view." In Haugeland, J., ed., Mind Design, chapter 4, pages 129-142. MIT Press, Cambridge, MA.
- (1982) "Representation and recognition of the movements of shapes." Proceedings of the Royal Society of London B, 214:501-524. (with L. M. Vaina)
- Marr D. (1982). "Vision. A Computational Investigation into the Human Representation and Processing of Visual Information. W.H. Freeman and Company.
- Marr D. (2010). "Vision. A Computational Investigation into the Human Representation and Processing of Visual Information.", The MIT Press. Foreword by Shimon Ullman, afterword by Tomaso Poggio.
- Vaina, L. M., ed. (1990). From the retina to the neocortex: selected papers of David Marr. Birkhauser, Boston, MA.
- McNaughton, B. L. (1990). "Commentary on Simple memory: a theory of the archicortex." pp. 121–128.
- Willshaw, D. J. and Buckingham, J. T. (1990). "An assessment of Marr's theory of the hippocampus as a temporary memory store." Proceedings of the Royal Society of London B, 329:205-215.
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