Vision in 1 Lecture

Prof. Jack PettigrewVision Touch and Hearing Research Centre, University of Queensland 4072 Australia.

Vision:

1. Parallel Visual Pathways:• Diversity of retinal ganglion cells and their destinations• E.g. Melanopsin and the circadian clock system: SCN , jet

lag etc• 2. “Ventral” (conscious) vs. “dorsal” (unconscious) visual

streamsBlindsight: Veridical vs. Non-veridical

(Blind spot)

Melanopsin-containinglight sensitive retinal ganglion cell

MM MM

M

PPDS PLS

Parallel Visual Paths: >9 Separate Destinations of Retinal Ganglion Cells

1. SCN of hypothalamus…melanopsin system.CIRCADIAN CLOCK

2. dLGN (4 P & 2M layers)..geniculostriate. CONSCIOUS VISION ………ventral (&dorsal) stream OBJECT

ID

3. Pulvinar-LP complex……MT…dorsal stream…..VISUOMOTOR

4. Pretectal complex…………….NEAR REFLEX TRIAD

5. Midbrain superior colliculus………VISUAL ORIENTATION

6. Accessory optic system…………….VISUAL STABILISATION

Dorsal TN, lateral TN, medial TN (pitch, roll & yaw)

7. Habenula, raphe etc ……………..

III

IV

III

IV

Forebrain

MidbrainHindbrain

AnterogradeTransportof ocular

label

1. SCN circadian clock• Input from melanopsin ganglion cells• 24 hr periodic expression of “Clock” genes• Interhemispheric oscillator

Characterised only in last decade

Labelling in Suprachiasmatic Nucleus (SCN): lac-Z-melanopsin construct

1. SCN circadian clock

2. dLGN geniculo-striate path• Huge in primates• Binocular vision emphasised: 3 layers for each eye• Conscious vision• Developmentally plastic

V1Striate cortex

1. SCN circadian clock

2. DLGN geniculostriate

3.Pulvinar-LP complexOld tectal system: primary system in most vertebratesDominated by striate input in primates

MT

1. SCN

2. dLGN

3.Pulvinar-LP complex 4. Pretectum

Near triad, focus, miosis, vergence

1. SCN circadian clock

2. DLGN geniculostriate

3.Pulvinar-LP complexOld tectal system

5. Midbrain-Sup.Colliculus:• orientation• “visual grasp reflex”• “hard wired:• lateral visual field

4. Pretectum

1. SCN

2. dLGN

3.Pulvinar-LP complex

6. Accessory Optic•DS ganglion cells•Stabilisation•Cerebellum•Vestibular interaction

4. Pretectum

5. Midbrain-Sup. colliculus

1. SCN

2. dLGN

3.Pulvinar-LP complex

6. Accessory Optic

4. Pretectum

5. Midbrain-Sup. colliculus

7. Habenula, Raphe?? Function•Colour spectrum mood•Visual input to “switch”

V1P

1. SCN

2. dLGN

3.Pulvinar-LP complex

6. Accessory Optic

4. Pretectum

5. Midbrain-Sup. colliculus

7. Habenula, Raphe

V1

MT

M

M

1. SCN

2. dLGN

3.Pulvinar-LP complex

6. Accessory Optic

4. Pretectum

5. Midbrain-Sup. colliculus

7. Habenula, RapheMM

M

V1

MT

DM

P

M

M

2. dLGN

3.Pulvinar-LP complex

5. Midbrain-Sup. colliculus

Dorsal Stream

M

M

M M

V1

MT

DM

P

M

M

2. dLGN

3.Pulvinar-LP complex

5. Midbrain-Sup. colliculus

Ventral Stream

M

M

M M

V1

MT

DM

P

M

M

2. dLGN

3.Pulvinar-LP complex

5. Midbrain-Sup. colliculus

Ventral Stream

M

M

M M

V1

MT

DM

P

M

M

2. dLGN

3.Pulvinar-LP complex

5. Midbrain-Sup. colliculus

Ventral Stream

M

M

M M

V1

MT

DM

P

M

M

Ventral Stream

IT

IT visual Cortex in temporal pole:•Complex object recognition, including faces (FF area)•Highly plastic (lesions here affect visual memory)•Major output projection to limbic system, hippocampus

Hierarchical; V1 V2 etc ITMultiply interconnected“Apex” of hierarchy is hippocampal cortexEach has complete representation of visual fieldFunctional specialisation (colour, motion,depth etc)

Dorsal Stream• V1, MT, DM, P• Precision place•“Where?”• M system• Unconscious• Veridical• No illusions

V1V2

MTV5

V3

FacesPlacesIT

IT

26

DM

S1S2 etcP

A1

Ventral Stream• V1,V2,V3,…..IT• Object identification •“What?”• P system• Conscious• Abstract• Illusions

Multiple visual cortical areas

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