Neural Stimulation, Learning and Masking
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Optical Illusion - Wikipedia, the Free Encyclopedia
Optical illusion - Wikipedia, the free encyclopedia Try Beta Log in / create account article discussion edit this page history [Hide] Wikipedia is there when you need it — now it needs you. $0.6M USD $7.5M USD Donate Now navigation Optical illusion Main page From Wikipedia, the free encyclopedia Contents Featured content This article is about visual perception. See Optical Illusion (album) for Current events information about the Time Requiem album. Random article An optical illusion (also called a visual illusion) is characterized by search visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are interaction different from the objects that make them, physiological ones that are the An optical illusion. The square A About Wikipedia effects on the eyes and brain of excessive stimulation of a specific type is exactly the same shade of grey Community portal (brightness, tilt, color, movement), and cognitive illusions where the eye as square B. See Same color Recent changes and brain make unconscious inferences. illusion Contact Wikipedia Donate to Wikipedia Contents [hide] Help 1 Physiological illusions toolbox 2 Cognitive illusions 3 Explanation of cognitive illusions What links here 3.1 Perceptual organization Related changes 3.2 Depth and motion perception Upload file Special pages 3.3 Color and brightness -
OPTICAL ILLUSIONS Matyas Molnar More Info, Examples, Sources
OPTICAL ILLUSIONS Matyas Molnar More info, examples, sources • Mohit Gupta: Understanding optical illusions • https://www.eyebuydirect.com/understanding-perception-optical-illusions • https://www.rd.com/culture/optical-illusions/ • https://www.thisisinsider.com/classic-optical-illusions-2018-1#this-is- troxlers-fading-circle-if-you-stare-the-dot-for-at-least-20-seconds-the-circle- will-completely-fade-away-20 • https://interestingengineering.com/11-puzzling-optical-illusions-and-how- they-work • https://www.collective-evolution.com/2017/07/26/ex-nasa-scientists-share- concealed-information-about-the-face-pyramid-found-on-mars/ • https://www.buzzfeed.com/arielknutson/people-who-found-jesus-in-their- food Preface • Microscopy is a visualization technique – the danger: we tend to believe what we see but humans are fooled by their vision in many different ways • We see / don’t see what we – want / don’t want to see – learnt / didn’t learn to se – others expect / don’t expect us to see • Humans are not rational beings. Our perception and decisions are governed by our emotions and earlier experiences. We make decisions emotionally, only later we justify them with logical explanations. • Biggest effects and limitations are in the following levels: – Eyes – Brain – Environment – Culture, religion, belief systems • We cannot perceive the world objectively outside of our box • Is there any objective world outside us? Preface • Many times there are no consensus on how an actual optical illusion works. • Hard to explain optical illusions with one unified theory, numerous factors are involved • There are various theories and counter theories, and sometimes it's also not clear if the illusion or type of illusion acts on the physical visual system or on the brain level. -
Understanding Optical Illusions
Understanding Optical Illusions Mohit Gupta What are optical illusions? Perception: I see Light (Sensing) Truth: But this is an ! Oracle Optical Illusion in Nature Image Courtesy: http://apollo.lsc.vsc.edu/classes/met130/notes/chapter19/graphics/infer_mirage_road.jpg A Brightness Illusion Different kinds of illusions • Brightness and Contrast Illusions • Twisted Cord Illusions • Color Illusions • Perspective Illusions • Relative Motion Illusions • Illusions of Expressions Lightness Constancy Our Vision System tries to compensate for differences in illumination Why study optical illusions? • Studying how brain is fooled teaches us how it works “Illusions of the senses tell us the truth about perception” [Purkinje] • It makes us happy J : Al Seckel Simultaneous Contrast Illusions Low-level Vision Explanation Negative Positive Photo-receptors Photo-receptors Receptive Fields in the Retina - Inhibitory Light Excitatory - + - Light - Low-level Vision Explanation - - - + - - + - Positive - - Negative Gradient Gradient High-level Vision Explanation: Context Less Incident More Incident Illumination Illumination Higher Perceived Lower Perceived Reflectance Reflectance Brightness = Reflectance * Incident Illumination The Hermann grid illusion The Hermann grid: Low level Explanation - - + - - Lateral Inhibition The Hermann grid illusion Focus on one intersection Why does the illusion disappear? Receptive fields are smaller near the fovea (center) of the eye The Waved Grid: No illusion! Scintillating Grids: Straight and Curved Adelson’s checkerboard -
Mariann Füzesiné Hudák UNDERSTANDING BASIC VISUAL
Budapest University of Technology and Economics PhD School in Psychology – Cognitive Science Mariann Füzesiné Hudák UNDERSTANDING BASIC VISUAL MECHANISMS THROUGH VISUAL ILLUSIONS PhD Thesis Supervisor: Dr. Ilona Kovács Budapest, 2013 ‘There is no harm in doubt and skepticism, for it is through these that new discoveries are made.’ (Richard Feynman, Letter to Armando Garcia J, December 11, 1985) 1 Acknowledgements .......................................................................................................................... 3 2 Abstract ............................................................................................................................................ 4 3 Kivonat ............................................................................................................................................. 4 4 Summary .......................................................................................................................................... 4 5 Összefoglaló ..................................................................................................................................... 5 6 Introduction ...................................................................................................................................... 7 6.1 Looking into the ‘black box’ through illusions - An alternative to physiological studies ...... 7 6.2 Theories of lightness-brightness perception .......................................................................... 12 6.2.1 The roots ........................................................................................................................... -
Visual Illusions 1077 Square on Top of 4 Disks Is Assumed
Visual Illusions 1077 square on top of 4 disks is assumed. Note that just inside its edges should also be present in its the completion of the boundaries of the Kanizsa middle. This is a symbolic (logical) operation square is accompanied by a surface filling-in pro- that might be carried out in the high-level visual cess that leads to the square being perceived as cortex. Some studies have failed to find evidence brighter than the surrounding white background. for the spread of information thought to underlie In a related process, the black disks are surface perception in early retinotopic visual completed “behind” the reconstructed surface. areas, and this has been taken by some as sup- Filling-in and completion processes related to port for symbolic theories of surface perception. visible figures (the Kanizsa square) are referred Hence, further empirical work is required to test to as “modal,” while these processes are referred the traditional view as well as symbolic theories, to as amodal when related to invisible parts of and to resolve some inconsistencies in the find- figures (the parts of the disks occluded by the ings among some studies. Because the traditional Kanizsa square assumed in front by the visual view and symbolic theories are not mutually system). exclusive, elements from both theories might find Figures 1(c) and (d) illustrate the existence of support in the future. surface filling-in processes. Figure 1(c) shows that the physical gray levels in between the black bars P. De Weerd are the same. When the black bars are removed, See also Consciousness; Gestalt Approach; Object some regions in the stimulus are seen as much Perception; Object Perception: Physiology; Perceptual brighter and others as darker, an illusion referred Organization: Vision to as the Craik-O’Brien-Cornsweet illusion. -
Scientific and Large Data Visualization 25 October 2018 Visual Perception Massimiliano Corsini Visual Computing Lab, ISTI
Scientific and Large Data Visualization 25 October 2018 Visual Perception Massimiliano Corsini Visual Computing Lab, ISTI - CNR - Italy Overview • Intro • Our Eye • Receptive Field Model, CSF, Mach Bending, Cornsweet effect.. • What we really see • Preattentive Process • Gestalt Laws • Perception of lines and areas Human Visual System (HVS) • The Human Visual System (HVS) is subdivided into two parts: – Optical part our eye. – Visual Perception our brain (visual cortex). Our Eye The Retina • The retina is composed by a large number of photoreceptors (rods and cones). • 100 millions of rods, 6 millions of cones. • Cones are concentrated in the fovea (1.5-2 degrees). • Retinal ganglion cells send information, through the optic nerve, to the brain. Rods and Cones Distribution Visual Acuity • Points – 1 minute of arc. • Gratings – 1-2 minutes of arc. • Letter – 5 minutes of arc. • Vernier acuity (the ability to see if two segments are colinear) – 10 seconds of arc. Visual Acuity Snellen Chart Visual Acuity Figure by Vanessa Ezekowitz under CC-SA-BY 3.0. Contrast Sensitivity Function (CSF) • Our perception is sensitive to pattern contrast, frequency and orientation. • Also color influences the CSF. Figure by Martin Reddy. Contrast Sensitivity Function (CSF) Visual Cortex • LGN (Lateral Geniculate Nucleus) forwards pulses to V1. It is also connected with V2 and V3. • V1 is the primary visual cortex. It performs edge detection and global organization (inputs from V2, V3). Visual Cortex • V2 handles depth, foreground, illusory contours. • V3 supports global motion understanding. • V4 recognizes simple geometric shape. • V5/MT: motion perception integration and eye movements guidance. Receptive Field (in the retina) • The receptive field of a cell is the visual area over which a cell responds to light. -
CROWN 85: Visual Perception: a Window to Brain and Behavior Lecture 6
CROWN 85: Visual Perception: A Window to Brain and Behavior Lecture 6 lecture 6 outline Crown 85: Visual Perception: A Window to Brain and Behavior Crown 85 Winter 2016 Visual Perception: A Window to Brain and Behavior Lecture 6: The Central Visual: System (structure and processing) Reading: Joy of Perception Eye Brain and Vision Web Vision Looking: Information Processing in the Retina (Sinauer) Visual Pathways (Sinauer) Phototransduction (Sunauer) Several Werblin Videos on Visual Cortex OVERVIEW: Visual information leaves the retina via the optic nerve and is transmitted to structures in the brain. The aim of this lecture will be to see various cortical sites further of the original “photograph” into new codes which emphasize certain aspects of the image while discarding others. We will discuss how this code is refined as information is transmitted Lecture 6: Central Visual System (Structure and Processing along pathways to the brain. 1 2 two important questions about cortical processing from outline 2. Understand the following functional concepts: What types of patterns selectively activate a. receptive field f. orientationally tuned cells in the visual system? b. concentric on-center neuron [receptive fields] receptive field g. simple cell c. concentric off-center h. complex cell receptive field i. "grandmother" cell d. retinotopic map j. spatial frequency detector Are differing aspects of an image processed e. feature detector k. what vs where pathways by different parts of the brain? [concurrent pathways or streams] 4 receptive rield (RF) Receptive Field (Kalat figure 6.18) Map of how light presented to various positions in the visual field excites or inhibits the firing of a neuron (this map or pattern is the cell’s receptive field). -
Visual Illusions
VISUAL ILLUSIONS: PERCEPTION OF LUMINANCE, COLOR, AND MOTION IN HUMANS Inaugural-Dissertation zur Erlangung des akademischen Grades Doctor rerum naturalium (Dr. rer. nat.) an der Justus-Liebig-Universität Giessen Fachbereich 06: Psychologie und Sportwissenschaften Otto-Behaghel-Strasse 10F 35394 Giessen vorgelegt am 21. Dezember 2006 von Dipl. Psych. Kai Hamburger geboren am 5. Juni 1977 in Gedern 1. Berichterstatter und Betreuer Prof. Karl R. Gegenfurtner, Ph.D. (Psychologie, Giessen) 2. Berichterstatter Prof. Dr. Hans Irtel (Psychologie, Mannheim) To my grandfather Heinrich, my parents Elke and Rainer, my brother Sven, and to my fiancée Sandra. Acknowledgement First of all, I would like to express my gratitude to my godfather in the graduate program, Professor Karl R. Gegenfurtner (Giessen, Germany), and my two other supervisors, Professor Lothar Spillmann (Freiburg, Germany) and Professor Arthur G. Shapiro (Lewisburg, PA, U.S.A.). Karl, on very short notice you gave me the opportunity to join the graduate program ‘Neural Representation and Action Control – Neuroact’ and by doing so one of the best departments in the field of Vision Sciences. I became a member of an extraordinary lab, which still excites me. You allowed me to finish projects which were already in progress when I started in Giessen and you gave me plenty of rope to pursue my own interests. Thus, I was able to publish efficiently and furthermore gained deep insights into the field of Vision Sciences and even beyond. This was the best mentoring a natural scientist could think of. Thank you. Professor Spillmann, you paved my way into the Vision Sciences. At the beginning of my scientific career you gave me the opportunity to join your famous ‘Freiburg Psychophysics Laboratory’. -
Ganglion Cells Are the Output Neurons of the Retina: They Produce a Train of Spikes
NATURAL AND ARTIFICIAL VISION MODULE 387AA – ROBOTICS [WIF-LM] Marcello Calisti [email protected] The BioRobotics Institute Scuola Superiore Sant’Anna Content of the lectures • Natural part – theorectical (3h) • Artificial part – theorectical (3h) • Hands-on in Matlab (6h) The material on natural vision can be found on: Kandel et al., “Principle of Neuroscience”, McGraw Hill, 2013 Most of the material presented in these lessons can be found on the brilliant, seminal books on robotics and image analysis reported hereafter: 1. P.I. Corke, “Robotics, Vision & Control”, Springer 2011, ISBN 978-3-642-20143-1 2. R. Szeliski, “Computer Vision: Algorithms and Applications”, Springer-Verlag New York, 2010 3. R.C. Gonzalez & R.E. Woods, “Digital Image Processing (3rd edition)”, Prentice-Hall, 2006 Most of the images of these lessons are downloaded from RVC website http://www.petercorke.com/RVC/index.php and, despite they are free to use, they belong to the author of the book. Human vision is a creative process, far beyond simple trasduction Psychol Sci. 2006 Apr;17(4):287-91. The impact of emotion on perception: bias or enhanced processing? Zeelenberg R1, Wagenmakers EJ, Rotteveel M. Psychol Sci. 2003 Jan;14(1):7-13. Emotional facilitation of sensory processing in the visual cortex. Schupp HT1, Junghöfer M, Weike AI, Hamm AO. what we can What we learnt What we want Light is «different» depending on the animal we insect Ludimar Hermann Shiny Herman grid We saw contrast, not absolute value of illumination The Craik-Cornsweet illusion -
Free-Energy and Illusions: the Cornsweet Effect 058 002 059 003 060 004 Harriet Brown* and Karl J
ORIGINAL RESEARCH ARTICLE published: xx February 2012 doi: 10.3389/fpsyg.2012.00043 001 Free-energy and illusions: the Cornsweet effect 058 002 059 003 060 004 Harriet Brown* and Karl J. Friston 061 005 The Wellcome Trust Centre for Neuroimaging, University College London Queen Square, London, UK 062 006 063 007 064 Edited by: 008 In this paper, we review the nature of illusions using the free-energy formulation of Bayesian 065 Lars Muckli, University of Glasgow, perception. We reiterate the notion that illusory percepts are, in fact, Bayes-optimal and 009 UK 066 010 represent the most likely explanation for ambiguous sensory input. This point is illustrated 067 Reviewed by: 011 Gerrit W. Maus, University of using perhaps the simplest of visual illusions; namely, the Cornsweet effect. By using 068 012 California at Berkeley, USA plausible prior beliefs about the spatial gradients of illuminance and reflectance in visual 069 013 Peter De Weerd, Maastricht scenes, we show that the Cornsweet effect emerges as a natural consequence of Bayes- 070 University, Netherlands 014 optimal perception. Furthermore, we were able to simulate the appearance of secondary 071 015 *Correspondence: illusory percepts (Mach bands) as a function of stimulus contrast. The contrast-dependent 072 Harriet Brown, Wellcome Trust Centre 016 073 for Neuroimaging, Institute of emergence of the Cornsweet effect and subsequent appearance of Mach bands were 017 Neurology Queen Square, London simulated using a simple but plausible generative model. Because our generative model 074 018 WC1N 3BG, UK. was inverted using a neurobiologically plausible scheme, we could use the inversion as a 075 019 e-mail: [email protected] simulation of neuronal processing and implicit inference. -
Sensorimotor Processing of Vertical Disparity
SENSORIMOTOR PROCESSING OF VERTICAL DISPARITY ROBERT SCOTT ALLISON A thesis submitted to the Faculty of Graduate Studies in partial fulfilment of the requirements for the degree of Doctor of Philosophy Graduate Programme in Biology York University Toronto, Ontario March 1998 Natioral Library Bibliothèque nationale 191 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington OttawaON K1AON4 Ottawa ON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or seIl reproduire, prêter, distribuer ou copies of ths thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/^, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otheIUrise de celle-ci ne doivent être imprimés reproduced without the author' s ou autrement reproduits sans son permission. autorisation. SENSORIMOTOR PROCESSING OF VERTICAL DZSPARITY by Robert S. Allison a dissertation subrnitted to the Faculty of Graduate Studies of York University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Permission has been granted to the LIBRARY OF YORK UNIVERSITY to lend or sel1 copies of this dissertation. to the NATIONAL LIBRARY OF CANADA to microfilm this dissertation and to tend or seil copies of the film, and to UNIVERSITY MICROFILMS to publish an abstract of this dissertation. -
Van Ee (1999) an Analysis of Binocular Slant Contrast
Perception, 1999, volume 28, pages 1121 ^ 1145 DOI:10.1068/p2961 An analysis of binocular slant contrast Raymond van Eeô, Martin S Banks½Á, Benjamin T Backus# School of Optometry and Vision Science Program, 360 Minor Hall, University of California at Berkeley, Berkeley, CA 94720-2020, USA; ô also at Helmholtz Institute, University of Utrecht, Princetonplein 5, NL 3584 CC Utrecht, The Netherlands; ½ also at Department of Psychology, University of California at Berkeley; # also at Department of Psychology, Stanford University, Stanford, CA 94305-4115, USA; e-mail: [email protected] Received 12 March 1999, in revised form 15 June 1999 Abstract. When a small frontoparallel surface (a test strip) is surrounded by a larger slanted surface (an inducer), the test strip is perceived as slanted in the direction opposite to the inducer. This has been called the depth-contrast effect, but we call it the slant-contrast effect. In nearly all demonstrations of this effect, the inducer's slant is specified by stereoscopic signals; and other signals, such as the texture gradient, specify that it is frontoparallel. We present a theory of slant estimation that determines surface slant via linear combination of various slant estimators; the weight of each estimator is proportional to its reliability. The theory explains slant contrast because the absolute slant of the inducer and the relative slant between test strip and inducer are both estimated with greater reliability than the absolute slant of the test strip. The theory predicts that slant contrast will be eliminated if the signals specifying the inducer's slant are consistent with one another.