Learning to see: The early stages of perceptual organization by Yuri Ostrovsky A.B. Computer Science Harvard College, 1998 SUBMITTED TO THE DEPARTMENT OF BRAIN AND COGNITIVE SCIENCES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN NEUROSCIENCE AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY SEPTEMBER 2010 ©2010 Yuri Ostrovsky. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part in any medium now known or hereafter created. Signature of Author: ___________________________________________________________________ Department of Brain and Cognitive Sciences September, 2010 Certified by: __________________________________________________________________________ Pawan Sinha Associate Professor of Computational Neuroscience Thesis Supervisor Accepted by:__________________________________________________________________________ Earl Miller Picower Professor of Neuroscience Director, Brain and Cognitive Sciences Graduate Program Learning to see: The early stages of perceptual organization by Yuri Ostrovsky Submitted to the Department of Brain and Cognitive Sciences September, 2010 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Neuroscience ABSTRACT One of the great puzzles of vision science is how, over the course of development, the complex visual array comprising many regions of different colors and luminances is transformed into a sophisticated and meaningful constellation of objects. Gestaltists describe some of the rules that seem to govern a mature parsing of the visual scene, but where do these rules come from? Are they innate—endowed by evolution, or do they come somehow from visual experience? The answer to this question is usually confounded in infant studies as the timelines of maturation and experience are inextricably linked. Here, we describe studies with a special population of late-onset vision patients, which suggest a distinction between those capabilities available innately and those which are crafted via learning from the visual environment. We conclude with a hypothesis, based on these findings and other evidence, that early-available common fate motion cues provide a level of perceptual organization which forms the basis for the learning of subsequent cues. Thesis Supervisor: Pawan Sinha Title: Associate Professor of Computational Neuroscience 2 3 Table of Contents Chapter 1. Introduction ......................................................................................................................................................... 5 1.1 “Maturation” versus “development” ............................................................................................................ 7 1.2 A brief history of visual development research ....................................................................................... 8 1.2.1 Early brain plasticity in vision .............................................................................................................. 9 1.2.2 Lower-level visual development ........................................................................................................ 12 1.2.3 Higher-level visual development ....................................................................................................... 15 1.3 Towards a theory of visual development ................................................................................................. 18 1.4 References ............................................................................................................................................................. 22 Chapter 2. The Case of SRD: Maturation versus experience ................................................................................ 27 2.1 Introduction .......................................................................................................................................................... 28 2.2 SRD: Case Description ...................................................................................................................................... 30 2.2.1 Family History and Early Childhood ................................................................................................. 30 2.2.2 Post-operative Experience .................................................................................................................... 31 2.3 Experimental assessment of SRD's visual function ........................................................................ 32 2.4 Discussion.............................................................................................................................................................. 36 2.5 References ............................................................................................................................................................. 38 2.6 Appendix: Supplementary material ............................................................................................................ 40 2.6.1 Basic Form Perception ........................................................................................................................... 41 2.6.2 Face Processing ......................................................................................................................................... 48 Chapter 3. Visual Parsing After Recovery from Blindness ................................................................................... 55 3.1 Introduction.......................................................................................................................................................... 56 3.2 Methods .................................................................................................................................................................. 58 3.3 Results ..................................................................................................................................................................... 60 4 3.4 Discussion.............................................................................................................................................................. 66 3.5 References ............................................................................................................................................................. 69 Chapter 4. An argument for Dynamic Bootstrapping as a theory of visual development ....................... 73 4.1 Introduction.......................................................................................................................................................... 73 4.1.1 The Historical Perspective .................................................................................................................... 74 4.2 Motivation towards an empiricist theory of visual development .................................................. 78 4.3 The Dynamic Bootstrapping hypothesis: The development of visual perceptual organization abilities through dynamic information ......................................................................................... 79 4.4 Evidence for the Dynamic Bootstrapping hypothesis ......................................................................... 80 4.4.1 Empirical/developmental evidence .................................................................................................. 81 4.4.2 Ecological/statistical evidence............................................................................................................ 82 4.4.3 Logistical evidence ................................................................................................................................... 82 4.5 Discussion.............................................................................................................................................................. 83 4.6 References ............................................................................................................................................................. 86 Chapter 5. Conclusion .......................................................................................................................................................... 89 5.1 Thoughts on the critical period .................................................................................................................... 89 5.2 Nature versus nurture ...................................................................................................................................... 92 5.3 Future directions ................................................................................................................................................ 94 5.4 Postscript ............................................................................................................................................................... 96 5.5 References ............................................................................................................................................................. 98 5.6 Acknowledgements ........................................................................................................................................ 100 5 Chapter 1. Introduction Vision – the ability to “see”—seems so natural and seamless to us that a casual student of the mind may not even consider this faculty as requiring study. The lay observer often