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3 Retina and Visual System M1 CNS Sequence Peter Hitchcock, Ph.D. Winter, 2009

4 The topic of today s lecture is the central visual pathways. I. anatomy of the eye II. laminar and cellular anatomy of the retina III. regional specializations of the retina IV. central visual pathways V. visual association cortex VI. subcortical projections of ganglion cell axons circadian rhythms pupilary light reflex VI. visual information processing

5 Schematic diagram of the eye. Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed.

6 The human retina has 10 layers retinal pigmented epithelium photoreceptor layer outer limiting membrane ONL; photoreceptor nuclei outer plexiform layer INL; horizontal, bipolar and amacrine cell nuclei inner plexiform layer ganglion cell layer optic fiber layer inner limiting membrane light information Source Undetermined

7 The retina consists of a direct pathway, photoreceptors - bipolar cells - ganglion cells. Information in the direct pathway is modified by horizontal and amacrine cells. c - cones r-rods b-bipolar cells h-horizontal cells a-amacrine cells g-ganglion cells Gray s Anatomy

8 Photoreceptors and processes of the RPE interdigitate, but form no specialized junctions. Functions of RPE: phagocytose photoreceptors transport and store Vit. A recycle photopigments absorb stray light regulate fluid levels in the sub-retinal space Retinal detachment occurs when fluid accumulates in the space between the retina and RPE and separates the retina from the RPE. This space was part of the third ventricle in the embryonic brain. Image of photoreceptors removed

9 Müller cells are a specialized type of radial glia Müller cells help maintain ionic balances within the extracellular spaces in the retina. They also form the inner and outer limiting membranes Images of Muller cells removed

10 The two classes of photoreceptors divide visible light into two domains: intensity and wavelength Rods dim light, monochromatic Cones bright light, 3 wavelength sensitive subgroups R. Young, wikipedia There are several inherited diseases that result in death of photoreceptors, e.g, retinitis pigmentosa, age-related macular degeneration.

11 Absorption spectra for rod and The 3 classes of cone photoreceptors Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed.

12 Regional specializations in the retina. macula (lutea) fovea Fundus photograph of living, human retina illustrating the vasculature, fovea and optic nerve head (disc) Source Undetermined

13 The fovea is an pit (excavation) in the retina, wherein the inner layers are dis- placed laterally. sclera RPE photoreceptors ONL INL IPL GCL RPE, retinal pigmented epithelium; ONL, outer nuclear layer; INL, inner nuclear layer IPL, inner plexiform layer; GCL, ganglion cell layer Source Undetermined

14 The fovea contains cone photoreceptors only (no rods) at an extremely high density. % photorecptors? cones - 5% rods - 95% Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed.

15 Density distribution of photoreceptors in the retina along a line passing through the fovea and optic disc. Source Undetermined

16 Source Undetermined optic nerve head

17 lamina cribrosa optic fiber layer optic nerve head retina blood vessels Source Undetermined

18 Find your blind spot! Using the diagram below, fixate on the star, close your left eye and hold the figure about 1.5 feet from your face. When the filled circle disappears, its image is on your blind spot. Frisko, wikimedia commons

19 Connections from the retina into the hypothalamus diencephalon and midbrain (only 4 will be described) Image of visual system connections removed

20 optic nerve hypthalamus optic chiasm optic tract (Meyer s loop) lateral geniculate nuc. optic radiations midbrain (superior colliculus & pre-tectum) primary visual cortex (area 17; striate cortex) Source Undetermined

21 T N N T L-lower retina (superior visual fields) L -loop (Meyer s) L -lingual gyrus N T T N Meyer s loop Cross section through optic chiasm cuneate gyrus lingual gyrus Source Undetermined

22 parieto-occipetal fissure (cuneate gyrus) superior lip CC calcarine sulcus inferior lip (lingual gyrus) Most of primary visual cortex, area 17, lies on the medial wall of the occipital lobe Source Undetermined

23 vertical meridian lower vertical meridian periphery fovea fovea upper vertical meridian Gray s Anatomy Source Undetermined

24 L=left eye R=right eye area 17 flattened and viewed from the surface, illustrating the complete pattern of ocular dominance columns Source Undetermined

25 These two regions are sometimes referred as the ventral stream (what is it?) and a dorsal stream (where is it?). Source Undetermined

26 Cortical lesions in ventral or dorsal stream produce unique perceptual deficits Source Undetermined

27 Source Undetermined

28 Source Undetermined

29 Additional Source Information for more information see: Slide 5: Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed. Slide 6: Source Undetermined Slide 7: Gray s Anatomy Slide 10: R. Young, Wikipedia, PD-SELF Slide 11: Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed. Slide 12: Source Undetermined Slide 13: Source Undetermined Slide 14: Hanes. Fundamental Neuroscience. Churchill Livingstone, nd ed. Slide 15: Source Undetermined Slide 16: Source Undetermined Slide 17: Source Undetermined Slide 18: Frisko, Wikimedia Commons, PD-SELF Slide 20: Source Undetermined Slide 21: Source Undetermined Slide 22: Source Undetermined Slide 23: Gray s Anatomy; Source Undetermined Slide 24: Source Undetermined Slide 25: Source Undetermined Slide 26: Source Undetermined Slide 27: Source Undetermined Slide 28: Source Undetermined