PERIPHERAL HUMAN COLOUR VISION; FROM CONE CONTRAST TO COLOUR PERCEPTION A THESIS SUBMITTED TO THE UNIVERSITY OF MANCHESTER FOR THE DEGREE OF DOCTOR OF PHILOSOPHY (PHD) IN THE FACULTY OF LIFE SCIENCES 2010 ATHANASIOS PANORGIAS CONTENTS Abstract 11 Declaration 13 Copyright statement 14 Acknowledgements 16 Alternative Format Thesis 19 Rationale and aims 21 1 General introduction 23 1.1 Overview of the visual process....................... 23 1.2 Physiology of the visual process...................... 24 1.2.1 First stage: Photoreceptors..................... 24 1.2.2 Post-receptoral neural organisation of the retina.......... 28 1.2.3 Second stage: Cone opponency.................. 30 1.2.4 Retino-thalamic pathways and cortex............... 33 1.3 Transformation from retina-LGN to cortex. Third stage: Colour opponency. 36 1.4 Individual variations in colour vision.................... 37 2 CONTENTS 1.5 Colour perception in peripheral retina................... 39 1.6 References.................................. 42 2 Materials and general methods 50 2.1 Colour space................................ 50 2.2 Cone fundamentals and L-, M-, S-cone activation units.......... 53 2.3 Cardinal directions, chromatic axes and purity............... 55 2.4 Cone opponent model............................ 58 2.5 Cone contrast................................ 59 2.6 Experimental equipment and calibration procedure............ 61 2.7 Experimental procedures and colour vision tests.............. 63 2.7.1 Colour vision tests......................... 63 2.7.2 Asymmetric matching paradigm.................. 65 2.7.3 Naming experiment......................... 69 2.8 Ethics.................................... 70 2.9 References.................................. 71 3 Nasal-temporal differences in cone opponency in the near peripheral retina 73 3.1 Abstract................................... 73 3.2 Introduction................................. 74 3.3 Methods................................... 76 3.4 Results.................................... 79 3.5 Discussion.................................. 83 3.6 References.................................. 87 4 Naming versus matching and the stability of unique hues 91 4.1 Abstract................................... 91 3 CONTENTS 4.2 Introduction................................. 92 4.3 Methods................................... 95 4.3.1 Stimuli............................... 95 4.3.2 Colour space............................ 95 4.3.3 Observers.............................. 96 4.3.4 Procedures............................. 97 4.4 Results.................................... 98 4.5 Discussion.................................. 102 4.6 References.................................. 106 5 Cone contrast in peripheral retina 109 5.1 Abstract................................... 109 5.2 Introduction................................. 110 5.2.1 Contrasted colours and colour constancy............. 111 5.2.2 Colour perception in the periphery................. 112 5.3 Methods................................... 114 5.3.1 Colour matching.......................... 115 5.3.2 Colour naming........................... 116 5.3.3 Cone contrast............................ 116 5.4 Results.................................... 117 5.5 Discussion.................................. 122 5.5.1 Peripheral L-, M- and S-cone contrast............... 123 5.5.2 Peripheral RMS cone contrast................... 124 5.5.3 The oddity of green......................... 126 5.5.4 Cone versus colour opponency................... 126 5.6 References.................................. 128 4 CONTENTS 6 Phases of daylight and the stability of colour perception in peripheral human retina 131 6.1 Abstract................................... 131 6.2 Introduction................................. 132 6.3 Methods................................... 137 6.3.1 Matching experiment........................ 138 6.3.2 Naming experiment......................... 139 6.4 Results.................................... 139 6.5 Discussion.................................. 145 6.5.1 Invariant blue and yellow...................... 146 6.5.2 Unique blue and yellow...................... 146 6.5.3 Inter-observer variability...................... 149 6.5.4 Conclusions............................. 151 6.6 References.................................. 153 7 Sex-related differences in peripheral human colour vision; a colour matching study 158 7.1 Abstract................................... 158 7.2 Introduction................................. 159 7.3 Methods................................... 164 7.4 Results.................................... 166 7.4.1 Hue rotation difference....................... 168 7.4.2 Saturation difference........................ 169 7.4.3 Chromatic channel difference................... 172 7.4.4 Female observers with wide anomaloscope matching range.... 173 7.5 Discussion.................................. 176 5 CONTENTS 7.6 References.................................. 181 8 Conclusions and future experiments 185 8.1 Conclusions................................. 185 8.2 Future experiments............................. 187 A CIE1976 Lu’v’ colour space 189 B Ellipses 192 B.1 References.................................. 195 C Non parametric statistical test for circular data 196 C.1 References.................................. 198 D Reprint: Nasal-temporal differences in cone opponency in the near periph- eral retina. 199 E Reprint: Naming versus matching and the stability of unique hues 200 Final word count: 36633 6 LIST OF FIGURES 1.1 Cone spectral sensitivities.......................... 26 1.2 Cone density................................ 27 1.3 The primate retinal neural circuitry..................... 29 1.4 Ganglion cell receptive fields........................ 32 1.5 Areas of the visual brain.......................... 35 1.6 Unique hues and cardinal cone opponent axes............... 37 2.1 Colour matching functions......................... 51 2.2 The CIE1931 xy colour space........................ 53 2.3 Smith and Pokorny (1975) cone fundamentals............... 54 2.4 CIE1931 xy colour space, cardinal axes and purity............ 56 2.5 Correspondence between chromatic axes and wavelengths........ 57 2.6 Visual channel activation.......................... 59 2.7 Cone contrast................................ 60 2.8 Monitor calibration - xy coordinates.................... 62 2.9 Monitor calibration - luminance...................... 62 2.10 Stimulus configuration........................... 66 2.11 Colour matching results in CIE1931xy.................. 67 2.12 Hue rotation and saturation match..................... 68 7 LIST OF FIGURES 2.13 Naming results............................... 69 3.1 Stimuli chromaticities in CIE1931 xy colour space............ 78 3.2 Nasal and temporal colour matches..................... 80 3.3 Cone opponency in the nasal and temporal visual field.......... 82 4.1 The CIE1931 xy colour space and the stimuli chromaticities....... 96 4.2 Unique hue settings at 1◦ and 10◦ eccentricity............... 99 4.3 Naming and colour matching results at 18◦ eccentricity.......... 100 5.1 Asymmetric peripheral colour matching; stimuli configuration...... 115 5.2 Colour matching and naming results.................... 118 5.3 Peripheral L-, M- and S-cone contrast................... 119 5.4 Probe versus test L-, M- and S-cone contrast for invariant and unique hues 121 5.5 Probe versus test RMS cone contrast.................... 122 6.1 The CIE1931 xy colour space, stimuli chromaticities and daylight locus. 138 6.2 Colour naming functions.......................... 140 6.3 Colour matching results on CIE1931 xy plot................ 141 6.4 Hue rotation and saturation match..................... 142 6.5 Variability ellipses............................. 144 6.6 Variability around the colour space..................... 145 6.7 Unique hues and daylight locus on cone space............... 148 7.1 Male and female colour matches on CIE1931xy colour space....... 167 7.2 Male and female hue rotation........................ 169 7.3 Male and female saturation match..................... 170 7.4 Male and female L-M channel activation.................. 172 7.5 Male and female S-(L+M) channel activation............... 174 8 LIST OF FIGURES 7.6 Male and female Nagel anomaloscope data................ 175 A.1 Colour matching results on CIE1976 u’v’ plot............... 190 9 LIST OF TABLES 4.1 Unique and invariant hues at 18◦ eccentricity for two observers...... 101 6.1 Unique hues at 18◦ eccentricity for three observers............ 140 7.1 CIE1931 xy probe chromaticity coordinates................ 166 10 ABSTRACT It is well known that the colour preferences of ganglion and LGN cells do not match the four perceptually simple colours red, green blue and yellow. It is also known that although colour perception is distorted in the peripheral visual field, there are four hues that appear stable with eccentricity. These are defined as peripherally invariant hues. Both of these observations must in some way reflect the physiological substrate of neurons at different stages of the primary visual pathway. The experiments described here are aimed at understanding the link between the physiology and the perception of colour by studying the characteristics of peripheral colour vision The following questions have been addressed: i) to what extent does colour matching rely on the retinal physiological substrate? ii) what is the reason for the discrepancy between invariant and unique green and how is cone contrast linked to this