Fundamentals of Human Neuropsychology, Sixth Edition Chapter 13 Lecture PPT

1. Bryan Kolb & Ian Q. Whishaw’s Fundamentals of Human Neuropsychology, Sixth Edition Chapter 13 Lecture PPT Prepared by Gina Mollet, Adams State College

2. The Occipital Lobes

3. Portrait: An Injured Soldier’s Visual World • P.M. • Struck by a bullet in the back of his brain • Lost sight in the right visual field • Could accurately guess about the presence or absence of light • Difficulty reading and recognizing faces

4. Anatomy of the Occipital Lobes • No clear division on lateral surface of brain • Medial Surface • Parieto-occipital surface • Calcarine Sulcus • Contains much of primary visual cortex • Separates upper and lower visual fields • Ventral Surface • Lingual gyrus • V2 and VP • Fusiform gyrus • V4

6. Subdivisions of the Occipital Cortex • Map based on monkey occipital cortex

7. Subdivisions of the Occipital Cortex • Roger Tootell • Map of human cortex

9. Subdivisions of the Occipital Cortex • Area V1 • Laminar organization most distinct of all cortical areas • Heterogenous • Has more than one distinct function • Preserved in V2 • Striate cortex • Another name for visual cortex due to its striped appearance

12. Subdivisions of the Occipital Cortex • Color Vision • Primary job of V4, but distributed throughout occipital cortex • Plays a role in detection of movement, depth, and position

13. Connections of the Visual Cortex • Connections • Primary Visual Cortex (V1) • Input from LGN • Output to all other levels • Secondary Visual Cortex (V2) • Output to all other levels • After V2 • Output to the parietal lobe - Dorsal Stream • Output to the inferior temporal lobe - Ventral Stream • Output to the superior temporal sulcus (STS) - STS Stream

15. Visual Pathways • Dorsal Stream • Visual Guidance of Movements • Ventral Stream • Object Perception • STS • Visuospatial functions

16. A Theory of Occipital Lobe Function • Vision begins in V1 (primary visual cortex), that is heterogeneous, and then travels to more specialized cortical zones • Selective lesions up the hierarchy produce specific visual deficits • Lesions to V1 are not aware of seeing

17. Visual Functions Beyond the Occipital Lobe • Vision-related areas in the brain make up about 55% of the total cortex • Multiple visual regions in the temporal, parietal, and frontal lobes • Vision • Not unitary, composed of many quite specific forms of processing • Five categories for vision

19. Five Categories of Vision • Vision for Action • Parietal Visual Areas in the Dorsal Stream • Reaching • Ducking • Catching • Action for Vision • Visual Scanning • Eye Movements and Selective Attention

22. Categories of Vision • Visual Recognition • Temporal Lobes • Object Recognition • Visual Space • Parietal and Temporal Lobes • Spatial location • Location of an object relative to person (egocentric space) • Location of an object relative to another (allocentric space)

24. Categories of Vision • Visual Attention • Selective attention for specific visual input • Parietal lobes guide movements and temporal lobes help in object recognition

25. Visual Pathways Beyond the Occipital Lobe • Milner and Goodale • The dorsal stream is a set of systems for on-line visual control of action • Evidence: • Visual neurons in the parietal cortex are active only when the brain acts on visual information • 3 pathways run from V1 to the parietal cortex, must be functionally dissociable • Visual impairments after parietal lesions can be characterized as visuomotor or orientational

27. Visual Pathways Beyond the Occipital Lobe • STS stream • Characterized by polysensory neurons • Neurons are responsive to both auditory and visual input or both visual and somatosensory input • Originates from structures in the parietal and temporal cortex

28. Imaging Studies of Dorsal and Ventral Streams • Haxby and colleagues • PET study • Found activation for facial stimuli in the temporal region and activation during a location task in the posterior parietal region and frontal lobes • Detection of motion activated V5, while detection of shape activated the STS • Color perception activated area V4

30. Disorders of Visual Pathways • Monocular Blindness • Loss of sight in one eye • Results from destruction of the retina or optic nerve • Bitemporal Hemianopia • Loss of vision from both temporal fields • Results from a lesion to the optic chiasm • Nasal Hemianopia • Loss of vision of one nasal field • Results from a lesion of the lateral chiasm

31. Disorders of Visual Pathways • Homonymous Hemianopia • Blindness of one entire visual field • Results from a complete cut of the optic tract, LGN or V1 • Macular sparing • Sparing of the central or macular region of the visual field • Results from a lesion to the occipital lobe

32. Disorders of Visual Pathways • Quadrantoanopia or Hemianopia • Complete loss of vision in one-quarter of the fovea or in one-half of the fovea • Results from a lesion to the occipital lobe • Field Defects • Scotomas - small blind spots • Results from small lesions to the occipital lobe

35. Disorders of Cortical Function • B.K.: V1 Damage and a Scotoma • Right infarct (dead tissue) in the occipital lobe • Experienced blindsight - could perceive location without perceiving content • Lost one-quarter of the fovea, poor vision in the upper left quadrant • Slow facial recognition

37. Disorders of Cortical Function • Case D.B.: V1 Damage and Blindsight • Had an angioma in the right calcarine fissure • Has a hemianopia • Cortical Blindness - blindsight in which he reports no conscious awareness of seeing but can report movement and location of objects

39. Disorders of Cortical Function • Case J.I.: V4 Damage and Loss of Color Vision • Sustained a concussion and suddenly lost color vision • Specific damage in the occipital cortex • Improved acuity at twilight or at night • Years later, no longer remembered color

40. Disorders of Cortical Function • Case P.B.: Conscious Color Perception in a Blind Patient • Suffered an ischemia that destroyed large area of the posterior cortex • Can only detect presence or absence of light and has intact color vision

41. Disorders of Cortical Function • Case L.M.: V5 (MT) Damage and the Perception of Movement • Vascular abnormality that produced bilateral posterior damage • Loss of movement vision • Unable to intercept moving objects by using her hand

42. Disorders of Cortical Function • Case D.F.: Occipital Damage and Visual Agnosia • Bilateral damage to the LO region and tissue between the parietal and occipital lobes • Visual form agnosia - inability to recognize line drawings of objects • Can use visual information to guide movements, but not to recognize objects

45. Disorders of Cortical Function • Case V.K.: Parietal Damage and Visuomotor Guidance • Bilateral hemorrhages in the occipitoparietal regions • Optic Ataxia - Deficit in visually guided hand movements

47. Disorders of Cortical Function • Cases D. and T.: Higher-Level Visual Processes • D • Right occipitotemporal lesion • Prosopagnosia - Facial recognition deficit • Could read lips • T • Left occipitotemporal lesion • Alexia - Inability to read • Impaired lip reading

48. Conclusions from Case Studies • Distinct syndromes of visual disturbance • Some provide evidence for a fundamental dissociation between the dorsal and ventral streams • Visual experience is not unified • Asymmetry in functions of occipital lobes

49. Visual Agnosia • Object Agnosia • Apperceptive Agnosia • Deficit in the ability to develop a percept of the structure of an object or objects • Simultagnosia • Unable to perceive more than one object at a time • Results from bilateral damage to the lateral parts of the occipital lobes • Associative Agnosia • Can perceive objects, but cannot identify them • Results from lesions to the anterior temporal lobes

50. Visual Agnosia • Other Agnosias • Prosopagnosia • Cannot recognize faces • Can recognize facial features, facial expressions, and tell human from nonhuman faces • Alexia • Inability to read • Form of object agnosia - inability to construct perceptual wholes from parts or • Form of associative agnosia - word memory is damaged or inaccessible • Results from damage to the left fusiform and lingual areas