1. Functional and Dysfunctional Anatomy of Visual Cortex Emily A Ulmer A, Stephanie M. Franczak B, Edgar DeYoe PhD C, Andrew P Klein MD C, Leighton P Mark MD C University Lake School, Hartland, WI A Divine Savior Holy Angels, Milwaukee, WI B Medical College of Wisconsin, Milwaukee, WI C

2. Purpose: The purpose of this exhibit is to demonstrate functional brain anatomy and deficit localization of vision cortex. Overview: Visual field topography is preserved on the retina, through visual pathways, and in the visual cortex. Functional brain mapping reveals the retinotopic organization of the visual cortex and can be used to understand and predict the location of scotoma. Divergent hierarchical and parallel processing of visual stimuli attributes generates the perception of color, form, motion and position. A ventral processing stream provides information to the temporo- occipital visual area, or the “What Area,” for visual object and color recognition processing. A dorsal processing stream provides information to the parietal visual area, or the “Where Area,” for higher visuospatial and attention processing. Each processing stream has multiple functional sub-streams and numerous interconnections. This tutorial reviews the functional organization of the visual system and associated deficits. For a more thorough review on the topic, see: 1.DeYoe, EA, Raut RV. Neuroimaging Clinics 24.4, Clinical Applications of Functional MRI, Elsevier, November 2014. Visual Mapping Using Blood Oxygen Level Dependent FMRI pg 573-584. 2. Jonathan D. Trobe, The Neurology of Vision Oxford University Press March 2001.V.

3. Overview

4. Image  Intensity  Wavelength  Time  Position  Eyes (R,L) Primary  Luminance  Spectral Feature-based  Contrast  Disparity  2-D velocity  2-D orientation 3D form  Shape  Size  Rigidity Surface properties  Color (brightness, hue, saturation)  Visual texture  Specular reflectance  Transparency (shadows & highlights) 3-D spacial relationships  Relative positions (X,Y,Z)  3-D orientation in space 3-D movement  Trajectory  Rotation Retinal imagesSensory Cues (V1)Inferred Attributes (extrastriate cortex) What is it? Where is it? The visual system engages in significant computational processing to transform simple retinal images and sensory cues, to infer attributes about the physical world V1 = 1 o visual cortex Extrastriate = association visual cortex Temporal visual cortex Parietal visual cortex

5. Take a minute to review the major visual pathways and functions Nasal half of left retina Temporal half of right retina Retina Lateral geniculate body (nucleus) Pulvinar Optic radiations (in retrolenticular limb of internal capsule) Superior colliculus Striate cortex Extrastriate cortex Meyer's loop Medial geniculate body Right lateral geniculate nucleus Brachium of sup. colliculus Visual cortex of right hemisphere Geniculostriate and Retinotectal Visual Systems  Geniculostriate system  Conscious visual perception  Pathway: Retina lateral geniculate nucleus (LGN) striate cortex extrastriate cortex  Retinotectal system (see Agarwal et al., EdE- 41, Neural Control of Ocular Movements)  Directing eye movements and visual attention  Pathway: Retina superior colliculus pulvinar extrastriate cortex  Visual reflex pathways (see Agarwal et al., EdE-41, Neural Control of Ocular Movements)  Accommodation (focusing the eye): Controls muscles of the ciliary body via a pathway through the cortex, pretectum, and ciliary ganglion. Contraction of the ciliary muscle causes thickening of the lens.  Pupillary control of light intensity: Constriction: Retinal signals control pupillary constrictor muscles via pathways through the pretectum, Edinger-Westphal nucleus, and ciliary ganglion Dilation: Retinal signals control dilator muscles via pathways through the spinal cord and superior cervical ganglion

6. Optic tract Chiasm LGN Meyers loop tract Radiations Visual cortex Fibers emanating from the LGN forming the optic radiation  Optic radiation:  Projects from the LGN to the primary visual cortex (V1)  Passes through the posterior (retro- lenticular) aspect of the posterior limb IC  Superior fibers course backward toward the occipital lobe  Inferior fibers course antero-inferiorly around the temporal horn before turning backwards (Meyer`s loop)  Optic radiation maintains retinotopic organization

7. RIGHT EYE VISUAL FIELDS Total blindness - Right eye Left superior quadrantanopia Bitemporal hemianopia Left homonymous hemianopia Left homonymous superior quadrantanopia Left homonymous hemianopia (macula spared) Optic nerve LEFT EYE Optic chiasm Optic tract Chiasm LGN Meyers loop tract Radiations Visual cortex Optic tract Lat. geniculate body Geniculo- calcarine tract or optic radiations Primary visual cortex (area 17) Meyer’s Loop has fibers from both eyes LEFT RIGHT Now that you have reviewed the geniculostriate pathway, try your luck at predicting visual field deficits. Click once for the lesion and a second time for the deficit.

8. Topography of the Visual System

9. Topography of the Visual System & Cortical Magnification A B LGN Visual field Retina Uncrossed fibers Crossed fibers  Preserved topography  Visual field topography is preserved on the retina  The topography of the receptor array (retina) is preserved in the LGN  The retinotopic organization of the LGN is maintained in the visual cortex  Foveal magnification  Foveal vision is magnified in the LGN and primary visual cortex  Magnification changes from 4 mm/degree to 0.5 mm/degree as the visual representation moves from 1 o to 25 o away from the center of gaze  One central degree of visual field is represented by 64 times the area of cortex than that devoted to the peripheral visual field  Foveal vision is represented in the cortex of the occipital pole Overlapping visual fields Left retina Projection on right retina Projection on left lateral geniculate body Optic nerve Optic tract Optic chiasm Lat. geniculate body Projection on right LGN Geniculocalcarine (optic) radiation Occipital Lobe Calc. fissure Projection on left occipital lobe Topography of the visual system

10.  There is hierarchical (more complex) processing of visual stimuli attributes from retina to higher-order visual areas  There is a relative divergence of processing of attributes (i.e. color, form, motion and position)  Ventral processing stream  Temporal visual area  Object /word/face/place recognition  “What area”  Dorsal processing stream  Parietal visual area  Visuospatial processing and visual attention  “Where area”  Each processing stream has multiple functional sub-streams with numerous interconnections Divergence of Hierarchical Visual Processing

11. Spatial relations Visual attention Identification Visual memory Motion The primary visual cortex (V1) is centered around the calcarine sulcus. Hierarchical processing occurs in association cortex along dorsal (parietal) and ventral (temporal) processing streams, becoming ever more complex

12. The type of visual deficit present depends on the location of the cortical lesion  Deficits:  V1, V2 – complete blindness of visual information  Occipital pole – central visual field deficit  Closer to parieto-occipital sulcus (POS) – peripheral visual field deficit  Higher visual areas – loss of different types of visual information processing such as shape, color, motion, and/or position  Specific deficits affected by involvement of dorsal or ventral processing streams

13. Ventral Stream Visual Deficits  Deficits of the ventral stream (ventral temporal area - VTA)  Visual object agnosia  Bilateral but left >right TVA  Prosopagnosia (faces)  Bilateral or right >>left TVA  Pure word alexia  Left TVA  Contralesional achromatopsia (lack of color recognition)  V4/VO  Color anomia (naming colors)  Left TVA  Visual amnesia  Bilateral or right >>left

14. Dorsal Stream Visual Deficits  Deficits of the dorsal stream (Parietal visual area - PVA)  Hemispatial neglect Right >>>Left PVA/angular gyrus, or frontal lobe, or pulvinar  Bilateral inattention Bilateral PVA  Acquired ocular motor apraxia Bilateral PVA  Optic ataxia Usually bilateral >> unilateral PVA  Impaired spatial relations Right >>>left parieto-occipital  Akinetopsia Bilat. hMT (Occ-temp-pariet jxn)

15. Retinotopic Mapping of Visual Cortex

16. Mapping eccentricity in 3 subjects The retinotopic organization of the visual cortex can be mapped with fMRI: Eccentricity 3D Flat Map

17. Polar angle mapping in 3 subjects The retinotopic organization of the visual cortex can be mapped with fMRI: Polar Angle 3D Flat Map

18. Functional field maps can be constructed from eccentricity and polar angle coordinates, relating activation to visual field locations

19. Composite eccentricity and polar angle maps can localize functional visual cortical areas

20. Cases: Apply Your Knowledge

21. Where is the infarct? (choose one) A.Right thalamus (MGN) B.Left thalamus (MGN) C.Right medial occipital lobe D.Left medial occipital lobe 48 yo with right visual field cut

22. D. Left medial occipital lobe 48 yo with right visual field cut Sulcal effacement

23. D. Left medial occipital lobe 48 yo with right visual field cut A visual field deficit may occur at several locations along the visual pathway. Tracing the pathways on CT in this case revealed subtle left occipital sulcal effacement, suggesting an infarct accounting for the contralateral visual deficit.

24. Where is the acute infarct? (choose one) A. Right corona radiata B. Right putamen C. Left posterior limb IC D. Left thalamus 68 yo with right visual field deficit

25. C. Left posterior limb internal capsule 68 yo with right visual field deficit

26. C. Left posterior limb internal capsule (PLIC) The infarct is located in the retro- lenticular portion of the internal capsule (bordering the posterior putamen), corresponding to anterio- posterior orientation of fiber bundles (green) at DTI. This area contains portions of non-motor fiber tracts such the optic radiation, the acoustic radiation, and is adjacent to somatosensory fibers. Thus, an infarct here may cause deficits in vision and audition, and somatosensory perception. Retro- lenticular portion of the PLIC

27. 59 yo RH patient with a ventral temporo-occipital infarct What is the most likely deficit? (choose one) A. Right hemi-spatial neglect B. Visuomotor dysfunction C. Optic ataxia D. Visual agnosia

28. 59 yo RH patient with a ventral temporo-occipital infarct D. Visual agnosia Visual spatial, visual motor, visual attention Object, word, place, face recognition Higher visual processing occurs along hierarchical dorsal and ventral processing streams. The temporal visual area (ventral processing stream) compares what one sees to visual memories, to provide recognition of objects, faces, places, and words (dominant hemisphere). Infarcts of the ventral visual areas may cause a class of deficits known as agnosias. Agnosia is the inability to recognize objects, places, faces, as well as words in the dominant hemisphere.

29. 53 yo with an occipital infarct What is the most likely deficit? (choose one) A. Left hemianopia B. Left upper quadrantanopia C. Left lower quadrantanopia D. Agnosia

30. 53 yo with an occipital infarct C. Left lower quadrantanopia Calcarine sulcus C Cuneus infarct The infarct is located in the supra- calcarine visual cortex (cuneus), which processes visual information from the lower visual field. Thus, a unilateral supra-calcarine occipital cortex infarct will result in a contralateral lower quadrantanopia. fMRI

31. 59 yo right handed patient with a right parietal infarct What is the most likely deficit? (choose one) A. Left hemianopia B. Left hemispatial neglect C. Aphasia D. Agnosia

32. 59 yo right handed patient with a right parietal infarct B. Left hemispatial neglect Hierarchical visual processing occurs along dorsal and ventral processing streams. Parietal visual areas (dorsal processing stream) process visual spatial and visual motor information, as well as support attention to visual stimuli. Cortex of the inferior parietal lobule is responsible for visual attention. The left parietal visual area (PVA) supports attention to the right visual hemi-field while the right PVA supports attention to both visual hemi-fields. Consequently, left PVA infarcts rarely cause hemi-spatial neglect, because the right PVA supports both hemi-fields. Right PVA infarcts on the other hand may cause left hemi-spatial neglect. It should be noted, however, that recent studies have questioned this classic model and suggest the organization may be more complex. Stay tuned… Visual spatial, visual motor, visual attention Object, word, place, face recognition

33. 8 yo female with refractory right hemispheric seizures and visuospatial dysfunction. Where is the abnormal cortex likely to be? Click once for answer

34. 8 yo female with visuospatial dysfunction, Answer: Right parietal visual area PET

35. Based on cortical retinotopy, what visual field deficits are at risk?

36. What visual field deficits are at risk? Click once for answer Answer: Peripheral vision is at risk along the posterior tumor border Eccentricity

37. What visual field deficits are at risk? What about white matter? Answer: Central and peripheral vision is at risk along the lateral border Eccentricity DTI Optic radiation

38. Conclusions  Understanding visual system functional and dysfunctional anatomy improves the accuracy of Neuroradiologic interpretations at standard MRI  Understanding visual system functional anatomy improves utilization of fMRI and DTI for presurgical planning  Understanding the effects of lesions on vision function provides a framework by which to guide surgical decision-making