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The Light and Dark of Visual Signal Processing

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The Light and Dark of Visual Signal Processing THE LIGHT AND DARK OF VISUAL SIGNAL PROCESSING Gloria Luo-Li A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Faculty of Medicine and Health The University of Sydney 2020 ii Acknowledgements Ten years ago, I was approached by a friend who advised me to extend my study in the field of medicine. I was excited about this idea and started exploring the journey. In 2012, I met Dr Alan Freeman who subsequently supervised my part-time project. Now, eight years later, my thesis is ready for submission! I knew that saying some general words of gratitude lack weight, however that’s the first and foremost way to express my appreciation. I am profoundly grateful to my supervisor Dr Alan Freeman for his unwavering support, insight and guidance and for his enthusiastic response to, and feedback on, every single step of the development of my project and extracurricular learning. Without the generous contributions of imparting his knowledge and confidence, this thesis would not be. I sincerely thank my associate supervisor Professor David Alais for his constant assistance by providing his laboratory for some of the experiments. Professor Alais always gives advice and comments positively and confidently to dispel my doubts and encourage me to work things through free of stress. I thank him from the bottom of my heart for his valuable contribution to my first published paper, Chapter 5 in this thesis, and his admirable attitude towards our relationship during the past eight-year research journey. To the American co-authors of my second published article – Distinguished Professors Alonso and Zaidi, and Dr Mazade, I thank them for their generosity far above what I asked or expected, by allowing me to use the data from their animal studies. They also made many thoughtful contributions throughout the drafting of Chapter 6. I cannot find the right words to express my endless appreciation to Professor Alonso and his team members who sacrificed their valuable time to support me so well. iii A special thank you goes to Dr Elaine Wong for her comments on this thesis, for her enthusiasm and generosity of sacrificing her own and family time working on my thesis, especially during the night-times after settling her newborn baby, for which I feel so thoroughly touched. To all the administrative staff, undergraduate and postgraduate students who participated in the experiments, I cannot thank them enough for being a part of my research. Thank you to Professor Frank Lovicu, Dr Peter Knight, Associate Professor Fazlul Huq, Dr Elizabeth Hegedus, Dr Jaimie Polson, Dr Darren Reed, Dr Helen Ritchie, Dr David Mor, and Dr Aaron Camp, who gave encouraging and assertive comments on each of my annual progress review reports. Thank you to Ms Felicia Lim, Dr Jin Huang, Dr Nastaran Hesam Shariati, Mr Gautham Jayachandran, Mrs Ann Korabelnikoff, Mrs Helen Ananin, Ms Ruth Rinot, Dr Md Sheikh Anwar, Dr Zaynab Al-Eisawi, and Dr Munira Al-Dossari, who gave me a helping hand whenever I needed it. A special thank you to Dr Patrick Lam, General Practitioner, Senior Lecturer and researcher in the field of biomechanics and orthopaedics at UNSW. Dr Lam generously shared his incredible ideas from his reflection on his experience in research and teaching. I thank him for inspiring me, and the time he sacrificed for reading and commenting as I drafted my thesis. Last, but not least, my heartfelt thanks to my family, especially my two teenage sons, for all your patience and loving encouragement throughout the years. To you, I dedicate this thesis. iv Brief contents Acknowledgements ...................................................................................................................... iii Brief contents ................................................................................................................................... v Detailed contents ............................................................................................................................ vi Summary ............................................................................................................................................ x Chapter 1. Literature review ...................................................................................................... 1 Chapter 2. Aims ............................................................................................................................. 29 Chapter 3. General methods .................................................................................................... 33 Chapter 4. Pilot study .................................................................................................................. 45 Chapter 5. Responses to light and dark stationary stimuli ............................................ 59 Chapter 6. Responses to light and dark moving stimuli .................................................. 73 Chapter 7. Mechanisms underlying motion direction selectivity ............................... 83 Chapter 8. Discussion ............................................................................................................... 111 References .................................................................................................................................... 118 Publications .................................................................................................................................. 128 v Detailed contents Acknowledgements ...................................................................................................................... iii Brief contents ................................................................................................................................... v Detailed contents ............................................................................................................................ vi Summary ............................................................................................................................................ x Chapter 1. Literature review ...................................................................................................... 1 Visual pathways ............................................................................................................................... 1 Overall structure of the visual pathways .......................................................................................... 1 Retinal structure ....................................................................................................................................... 3 Major retinal signal processing pathways ....................................................................................... 4 Centre-surround receptive fields ........................................................................................................ 5 Bipolar cell function ................................................................................................................................ 8 Retinal ganglion cell function ............................................................................................................. 10 Lateral geniculate nucleus ................................................................................................................... 11 Cellular structure of the primary visual cortex ............................................................................ 12 Cortical receptive fields ........................................................................................................................ 14 Conclusion ................................................................................................................................................. 15 Light/dark response asymmetries ......................................................................................... 15 Motion sensitivity ......................................................................................................................... 17 Neurophysiology of motion sensitivity ........................................................................................... 17 Subcortical mechanisms ....................................................................................................................... 18 Cortical mechanisms .............................................................................................................................. 20 vi Mechanisms underlying direction selectivity ............................................................................... 26 Chapter 2. Aims ............................................................................................................................. 29 Chapter 4 aims ......................................................................................................................................... 29 Chapter 5 aims ......................................................................................................................................... 29 Chapter 6 aims ......................................................................................................................................... 30 Chapter 7 aims ......................................................................................................................................... 30 Chapter 7 aims ......................................................................................................................................... 31 Chapter 7 aims ........................................................................................................................................
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