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VISUAL PERCEPTION an Information-Based Approach to Understanding Biological and Artificial Vision

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VISUAL PERCEPTION an Information-Based Approach to Understanding Biological and Artificial Vision VISUAL PERCEPTION An Information-based Approach to Understanding Biological and Artificial Vision by Noel A. Murphy B.A.(Mod) Submitted in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY Supervised by Prof. Charles McCorkell School of Electronic Engineering Dublin City University Dublin 9 Ireland September 1992 I hereby certify that this material, which I now submit for assessment on the programme of study leading to the award of Doctor of Philosophy is entirely my own work, and has not been taken from the work of others save and to the extent that such work has been cited and acknowledged within the text of my work Dedication To Karina, for all her love, support, patience and understanding, especially over the last three years. To Mum and Dad, Brigid and Michael Murphy, who have given me enormous support right through my education and who have never seen me lacking for anything. Acknowledgements I would like to thank my supervisor, Prof. Charles McCorkell, a man of great patience and forbearance for giving me the opportunity to cany out this work at a critical stage of my career, for giving me the opportunity to discover that lecturing (in moderate quantities) and research (in immoderate quantities) were two things that I would find enormously fulfilling, and for the constant help, support and guidance throughout the long road to this dissertation. I have had contact with many fellow students, and students of my own, in my years in the NIHE and now DCU. Particular names that spring to mind are Brian Buggy who started the same week as me and was a great friend and colleague throughout, Gearoid Mooney, Mark McDonnell, Jim Gunning and the many fourth-year B.Eng project students and who helped in various aspects of the project. For their interest, support and encouragement I am very greatful. The staff in the School of Electronic Engineering, DCU have been very supportive and cooperative in all the time I have worked with them, and for this I would like to heartily thank them. In particular I owe an enormous debt to Barry McMullin who introduced me to much of the literature which I have found most valuable, who kept me in touch with the outside world, who was always available to discuss and debate ideas which at the time seemed to have little place in an engineering department, and for the effort he put into organising the workshop on Autopoiesis & Perception held in DCU, August 1992, while he was preparing his own Ph.D. thesis. Also I am very greatful for the support and encouragement of Paul Whelan and Niall Byrne — Paul for his organisational contributions to the Advanced Vision Systems Group and the vision lab in DCU over the last two years, Niall for assisting in the preparation of various papers and presentations and for proofreading parts of this dissertation. John Whelan and his cohort of merry technicians were always there to sort out our problems, even the equipment ones, and their work and assistance is much appreciated. I would like to thank Dr Eugene Kennedy, and Dr Michael Clancy who supported the initial setting up of this project, and the National Board of Science and Technology (NBST), now called EOLAS, who provided funding for the first two years work. Table of Contents Acknowledgements ............................................................................................... iii Abstract ....................... vii List of Tables & Figures ..................................................................................... ix Preface .................................................................................................................x List of Publications .................................................... xxiii 1 Introduction ......................................................................................................... 1 1.1 Biology and Vision Engineering ............, ........................................... 1 1.2 Objectives................................................................................................ 6 1.2.1 Understanding the nature of perceptual processes ................ 8 1.2.2 Understanding the nature and role of information ................ 10 1.3 Cognitive Science .................................................................................. 11 1.3.1 Representational view of reality ............................................. 13 16 1.4 The Control/Autonomy D uality............................................................ 18 1.5 Descriptions and Explanations...............................................................20 1.6 Summary of Chapters of Dissertation................................................... 22 2 The Philosophy of Perception ...................................................... 30 2.1 Introduction.......................................................................................... 30 2.2 The Controversy of Universals............................................................... 31 2.2.1 R ealism .................................................................................... 32 2.2.2 Aristotelian duality ................................................................. 35 2.2.3 Aristotelian causality and complex systems ........................ 36 2.2.4 Anti-realism .......................................................................... 40 2.3 Similarity and Radical Nominalism ..................................................... 45 2.3.1 Theorem of the ugly duckling ................ 46 2.3.2 Axiology and radical nominalism ............................................47 2.4 Induction and Deduction ...................................................................... 48 2.4.1 Induction and evidence .......................................................... 49 2.4.2 Probabilistic interpretation of induction ............................... 51 2.4.3 The necessary view of probability......................................... 54 2.4.4 Abduction ............................................................................... 55 2.5 The Purpose of Perception ................................................................... 55 2.5.1 The eye/camera analogy.......................................................... 57 2.5.2 The status of functional explanations of perception 58 2.5.3 An approach to understanding perception............................. 60 2.6 Summary ................................................................................................ 62 3 Natural Visual Perception: The Retina ............................................................ 63 3.1 Introduction............................................................................................. 63 3.2 Retinal Structure .................................................................................... 64 3.3 Fovea .................................................................................................... 66 3.3.1 Foveal acuity ................ 66 3.3.2 Information processing implications of acuity....................... 68 3.3.3 Colour transduction....................................................................70 3.4 Extrafovea................................................. 72 v 3.4.1 Extrafoveal sampling..............................................................72 3.4.2 Extrafoveal function ...............................................................74 3.5 Receptive Fields and Point Images ..................................................... 75 3.5.1 Receptive fields and feature-detection theories .......................75 3.5.2 Point image and retinotopic m a p s ......................................... 77 3.6 Retinal Neurons — Processing, Function and Structure...................... 81 3.6.1 An overview of the cat re tin a ................................. 81 3.6.2 More retinas, more functions, more complexity.................... 85 3.6.3 The ganglion cells — a biological film ? ............................... 89 3.7 Neural Coding ...................................................................................... 93 3.7.1 Noise in the compound retina of the f l y ............................... 93 3.7.2 Neural predictive coding ........................................................ 96 3.7.3 Matched gain ..................... 98 3.7.4 Alternative theories of neural function................................ 100 3.7.5 Edges or artifacts: the Mach band phenomenon ....... 103 3.8 Summary ............................................................................................. 103 4 Information in Perception ............................................................................... 105 4.1 Introduction........................................................................................... 106 4.1.1 Information in physics.......................................................... 108 4.2 The Mathematical Theory of Information ......................................... I l l 4.3 Gabor’s Theory of information .......................................................... 115 4.4 Sampling and Quantization.................................................... 122 4.4.1 Isopreference curves ................................................... 122 4.4.2 The human spatial M T F ....................................................... 124 4.5 Entropy and Structure ........................................................................ 128 4.6 Linsker’s Neural Information-processing Principle........................... 130 4.7 Statistical and Form Redundancy ....................................................
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