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Psyc 351: Psychology of Perception

Week 4Eye, Brain and the Visual Pathways

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Adult human eye, axial cross-section, right eye seen from above

Cornea (“hornlike”)IrisScleraPupil

LensHumorsRetinaChoroid / Tapetum

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Adult human eye, axial cross-section, right eye seen from above

Pupil diameter 

Depth of field

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Pupil SizeA= πr 2 , thus a16-fold increase in light transmission

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Pupil Diameter & Depth of Field

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Horizontal pupils, dilated verticals

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Insects’

compoundeyes

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Accommodation and refraction by cornea and lens

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Adult human eye, axial cross-section, right eye seen from above

Refractive errors:

spherical and cylindrical

MyopiaHyperopia

Astigmatism

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Refractive errors

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Floaters

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Blood

vessels

in the

eye

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The

Retina

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Retina

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The

Retina

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Rods (120 million/eye)

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Cones (8 million/eye)

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Retina, continued

• Duplex structure: Photopic and Scotopic

• Collector cells (Horizontal and Amacrine)

• Sensitivity - acuity tradeoff 

• Bleaching of photopigments

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Pathways to the Brain

Optic nerve, myelin sheath

Optic chiasmLateral geniculate

Visual cortex

Retinotopic mapsPrimate cortex

Wiring diagram

Dorsal vs. Ventral Routes

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Pathways to the BrainOptic nerve, myelin sheathOptic chiasm

Lateral geniculate

Visual cortex

Retinotopic maps

Primate cortex

Wiring diagram

Dorsal vs. Ventral pathways

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Pathways to the BrainOptic nerve, myelin sheath

Optic chiasmLateral geniculateVisual cortexRetinotopic maps

Primate cortex

Wiring diagram

Dorsal vs. Ventral Routes

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Pathways to the BrainOptic nerve, myelin sheath

Optic chiasm

Lateral geniculateVisual cortex

Retinotopic maps

Primate cortex

Wiring diagram

Dorsal vs. Ventral

pathways

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PathwaysOptic nerve, myelin sheath

Optic chiasm

Lateral geniculate

Visual cortexRetinotopic maps

Primate cortex

Wiring diagram

Dorsal vs. Ventral paths

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Pathways to the BrainOptic nerve, myelin sheath

Optic chiasm

Lateral geniculate

Visual cortex

Retinotopic mapsPrimate cortex

Wiring diagram

Dorsal vs. Ventral paths

P th

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PathwaysOptic nerve, myelin sheath

Optic chiasm

Lateral geniculate

Visual cortex

Retinotopic mapsPrimate cortexWiring diagram

Dorsal vs. Ventral paths

P th

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PathwaysOptic nerve, myelin sheath

Optic chiasm

Lateral geniculate

Visual cortex

Retinotopic mapsPrimate cortexWiring diagram

Dorsal vs. Ventral paths

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Coding Processes in Vision

Steady state vs. change

Conceptual model of retinaLateral inhibition: Limulus, eye

Receptive fields

LGN receptive fieldsSimple cells

Motion cells in Area MTHypercolumns

V1 – V5 Summary

Grandmother cells

C di

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cells

Motion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

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C di

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fieldsSimple cells

Motion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

C di

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cellsMotion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

C di

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cells

Motion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

Coding

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cells

Motion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

Coding

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cells

Motion cells in Area MT

HypercolumnsV1 – V5 Summary

Grandmother cells

Coding

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CodingSteady state vs. change

Conceptual model of retina

Lateral inhibition: Limulus, eyeReceptive fields

LGN receptive fields

Simple cells

Motion cells in Area MT

HypercolumnsV1 – V5 SummaryGrandmother cells

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“The Movies in our Eyes”Frank Werblin & Botond Roska

Scientific American, April 2007

Key idea: the retina not only provides

Image sharpening through lateral

Inhibition and color separation.

It provides up to 12 real-time “movies”

coding for abstract properties

in the image.

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Human Behavioral Evidence

• Hermann Grid

• Mach Bands, model• Aftereffects: McCollough, tilt, waterfall

• Fortification images

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Human EvidenceHermann GridMach Bands, model

Aftereffects:

McCollough

TiltWaterfall

Fortification images

Human

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Human

EvidenceHermann Grid

Mach Bands, model

Aftereffects:McCollough

Tilt

Waterfall

Fortification images

Human

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Human

EvidenceHermann Grid

Mach Bands, model

Aftereffects:McCollough

Tilt

Waterfall

Fortification images

Human

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Human

EvidenceHermann Grid

Mach Bands, model

Aftereffects:McCollough

Tilt

Waterfall

Fortification images

[Excel implementation of model]