1. Maps Plasticity of maps Retinotopic map Last Lecture

2. More: Retinotopic Map Parallel Visual Pathways Blindsight Today’s Outline

3. Visual world onto the retina LVF Left Nasal retina Right Temporal retina RVF Left Temporal retina Right Nasal retina Retinotopic Map

4. Left Eye’s View Retinotopic Map

5. Right Eye’s view Retinotopic Map

6. Perimetric testing to Diagnose field defects View from above Retinotopic Map

7. Each eye’s field of View (visual field) is mapped out Can light be detected throughout the visual field? Retinotopic Map

8. Left Right VF Left EyeVF Right Eye Combined Visual Field Retinotopic Map

9. Left Right VF Left EyeVF Right Eye Combined Visual Field Retinotopic Map

10. Function: Perimetric Map shows blindness in lower right quadrant of… Left EyeRight Eye Where is the damage? Retinotopic Map

11. On the retinae? Retinotopic Map

12. From Retina to Brain Geniculo-Striate Pathway Optic nerve carries signals from retina. Decussation at optic chiasm (optic tract) Synapse at Thalamus: Lateral Geniculate Nucleus (LGN) Optic radiations to AREA 17; Striate Cortex, Primary visual cortex Retinotopic Map

13. Visual World Mapped onto Cortex (via the retina) >> retinotopic map Retinotopic Map

14. Deficit in 1/2 VF (homonymous: both eyes) Retinotopic Map CALCARINE FISSURE Upper Bank Lower Bank

15. Function: Perimetric Map shows blindness in lower right quadrant of… Left EyeRight Eye Where is the damage? Retinotopic Map

16. defect affects 1/4 VF Retinotopic Map

17. An area of visual loss surrounded by relatively well-preserved vision. Size and shape vary. Retinotopic Map

18. Gordon Holmes (1919) Correlated Visual Field Defects with lesion locus to identify the Retinotopic map. Retinotopic Map

19. Sensitive areas are “magnified” Field of View Cortical Map of Visual Field Retinotopic Map

20. Equi-visibility chart Objects in the periphery must be Physically larger in order to be as visible as objects falling on fovea Fovea is more sensitive Cortical Magnification Anstis Retinotopic Map

21. Fovea is a small portion of retina Retinotopic Map

22. Cortical Magnification Area 17 neurons have receptive fields in the retina More neurons have foveal receptive fields Retinotopic Map

23. Retinotopic map: Summary Crossed organization Left 17 --> RVF Right 17 --> LVF Inverted organization Lower calcarine > Upper VF Upper calcarine > Lower VF Fovea: Disproportional representation cortical magnification NOTE: Each visual cortex represents a visual field NOT an eye. Retinotopic Map

24. VF Left EyeVF Right Eye Combined Visual Field Left Right Nasal Retinotopic Map

25. Left Right Nasal VF Left EyeVF Right Eye Combined Visual Field Retinotopic Map

26. Left Right Nasal VF Left EyeVF Right Eye Combined Visual Field Retinotopic Map

27. For your review: the connections Left Eye Nasal hemiretina- LVF- projects to right hemisphere Temporal hemiretina- RVF- projects to left hemisphere To cross at optic chiasm uncrossed Right Eye Nasal hemiretina- RVF- projects to left hemisphere Temporal hemiretina- LVF- projects to right hemisphere nasal LVF input to Rhem.RVF input to LHem LEFT EYE’s RETINA RIGHT EYE’s RETINA

28. The Retinotopic Map Parallel Visual Pathways Blindsight Outline

29. Parallel Pathways From Retina To primary visual cortex To superior colliculus Parallel Pathways Path to SC

30. LGNStriate extra Striate LORE of neurology until the early 70's... Vision requires Area 17…or maybe not? Reports of residual vision in Animals with striate lesions (hamsters; monkeys): Recovery after experimental field defects (cortical ablations) spared light/dark discrimination spared localization abilities Implication: Other pathways can compensate for some geniculo-striate function. Can this also be true in humans?? Parallel Pathways