VISUAL SYSTEM Key points Relations of neural retina to other structures in the eye
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VISUAL SYSTEM Key points Relations of neural retina to other structures in the eye Knowledge of types of photoreceptor and their distribution across the retina Foveal versus peripheral retina Knowledge of the different cell types that make up the retina There are different types of retinal ganglion cell – thus parallel outputs from the retina and beyond…. Central visual pathways – projections to LGB and other subcortical visual structures Organization of visual fields – partial decussation at optic chiasm, binocularity, topography Projection to primary visual cortex – optic radiations Effects of lesions on visual function Reading Nolte (4th Ed), pgs 397-431 Crossman and Neary, pgs 129-133
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VISUAL SYSTEM Key points Relations of neural retina to other structures in the eye Knowledge of types of photoreceptor and their distribution across the retina Foveal versus peripheral retina Knowledge of the different cell types that make up the retina - PowerPoint PPT Presentation
Transcript of VISUAL SYSTEM Key points Relations of neural retina to other structures in the eye
VISUAL SYSTEMKey pointsRelations of neural retina to other structures in the eyeKnowledge of types of photoreceptor and their distribution across the retinaFoveal versus peripheral retinaKnowledge of the different cell types that make up the retinaThere are different types of retinal ganglion cell – thus parallel outputs from the retina and beyond….Central visual pathways – projections to LGB and other subcortical visual structuresOrganization of visual fields – partial decussation at optic chiasm, binocularity, topographyProjection to primary visual cortex – optic radiationsEffects of lesions on visual function
ReadingNolte (4th Ed), pgs 397-431 Crossman and Neary, pgs 129-133Fitzgerald, pgs 189-196, 201-202Kiernan (7th Ed), pgs 364-381Pritchard and Alloway, pgs 283-315
The human eye
Mouse retinal wholemount
NB Retina and optic nerve are derived from the neural tube – are of CNS origin
Photoreceptors
rods cones
LIGHT
light
light
130 million rods – monochromatic – high sensitivity – convergence
7 million cones – colour – central retina – high acuity – photopic vision
1 million retinal ganglion cells per eye – efferent cell
Cone photopigments
Retinal circuitry
Photoreceptors
Horizontal cells
Bipolar cells
Amacrine cells
Ganglion cells
ONL
OPL
INL
IPL
GCLoutput signals
light
conerod
There are different classes of retinal ganglion cell:
On/off cells, large and small receptive fields, sustained versus transient responses, monochromatic versus colour……(etc!!)
Visual Pathways
• Retina (rods, cones, fovea)– bipolars– ganglion cells - optic nerve
• Chiasm (nasal fibres cross)• Optic tract
– suprachiasmatic nuclei (diurnal rhythms)– pretectum (for eye movements)– superior colliculus (new objects, co-ordination of eye and
head/neck movements)– lateral geniculate body of the thalamus (to cortex)
Visual fields and central visual pathways in the human
Lateral geniculate nucleushuman monkey
Visual topography – maps
Control of Eye Movements• Medial longitudinal fasciculus connects all the cranial
nerve nuclei (III, IV, VI) together• Descending cortical input• Input from superior colliculus• Input from ascending cervical proprioception
Optic ReflexesPupillary constriction (Edinger-Westphal)due to light (consensual…both eyes at once)On accommodation - convergence
Classes of RGC
• CAT– On/off cells– sustained X/transient Y– not much colour
• MONKEY– On/off– Parvo (P) colour
(red/green) and form– Magno (M) motion
Monkey area 17 (V1)
Ocular dominance stripes in layer IV
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