Visual Perception Components

• Lens, cornea
• Retina
• Axon tracts to thalamus then occipital lobe
• Occipital lobe visual cortex

• Photoreceptors (cones and rods)
• Bipolar cells
• Ganglion cells
• Axons form optic nerve

1. Optic nerve: Retina to optic chiasm
2. Optic tract: optic chiasm to thalamus (LGB)
3. Optic radiation: thalamus to occipital lobe
1. geniculocalcarine fibers

• Focused representation of visual field
• Reverse of visual
• Left -> right
• top -> bottom

• Primary visual cortex
• midsagittal occipital lobe
• Point to point representation
• Retina through LGB to occipital lobe
• Bilateral projections
• Each eye => both hemispheres
• Allows for binocular vision

• Optic nerve (CN II)
• R/L converge at optic chiasm
• nasal retinal field fibers cross over
• temporal retinal field fibers remain ipsilateral
• Optic tract fibers
• Geniculocalcarine fibers
• optic radiation
• Occipital lobe

1. Where does the right visual field end up?
2. Where does the left visual field end up?
3. What happens at the optic chiasm?

1. Left hemisphere
2. Right hemisphere
3. partial crossover
1. nasal field cross over
2. temporal field stay ipsilateral
3. RVF -> LH
4. LVF -> RH

• Unilateral CN II cut between retina and chiasm
• Loss of vision in ipsilateral eye

• Loss of vision in temporal visual fields
• creates tunnel vision
• Damage to optic chiasm
• Lesion to fibers crossing at chiasm
• Pituitary gland tumor

• Loss of vision in nasal field unilaterally
• Lateral edge of optic chiasm
• Affects fibers from ipsilateral temporal retina (ipsilateral nasal visual field)

• Loss of same visual half (R/L) in each eye
• Interruption of optic tract, LGB or geniculocalcarine fibers

• Superior or inferior quandrant contralateral to lesion
• Interruption of portion of geniculocalcarine fibers

Primary visual cortex lesions

and

Cortical blindness

• Lesion to visual cortex unilaterally -> blindness in opposite field of vision in each eye
• Central vision usually spared
• Cortical blindness: bilateral cortical lesions
• can follow light only

• Broadman's areas 18 and 19
• Connections to temporal and parietal lobes; pulvinar
• Synthesize info; visual perception
• recognizing objects, forms, faces, color
• Link visual object to meaning, memories, significance
• Reading, writing

• Ventral pathway
• To inferior temporal lobe
• Damage -> agnosias: inability to recognize objects, words, faces

• Dorsal pathway
• To parietal lobe
• Damage -> inability to localize items
• can recognize/describe item
• cannot ID location (point to it)
• visual disorientation
• Topographic abilities
• Map reading, navigation

• Deficit in recognizing items
• Apperceptive
• Associative
• Prosopagnosia

• Difficulty recognizing or attaching meaning to an item with preserved perception
• Visual and tactile agnosia

1. Achromatopsia
2. Akinetopsia
3. Alexia without agraphia

• reading deficit without writing deficit
• Lesion to corpus callosum and occipital cortex

From top to bottom

1. Monocular blindness
2. Bi-temporal, heteronymous hemianopia
3. Homonymous hemianopia
4. Homonymous R/L quandrantanopsia
5. Primary visual cortex lesionsdamage at the Striate cortex

1. Visual field of left eye
2. Visual field of right eye
3. Temporal half of left retina
4. Nasal halves of retinas
5. Temporal half of right retina
6. Optic Nerve
7. Optic chiasm
8. Optic Tract
9. Geniculo-calcarine tract
10. Lateral geniculate body
11. Primary visual area or striate cortex
12. inverted
13. fields

1. Left visual field
2. right visual field
3. temporal
4. nasal
5. temporal
6. optic chiasm
7. pulvinar nucleus
8. lateral geniculate nucleus
9. superior colliculus
10. optic radiation
11. primary visual cortex