1. Human Neuropsychology,
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
Primary Visual Cortex (V1)
Input from LGN
Output to all other levels
Secondary Visual Cortex (V2)
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 Ventral Stream STS
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 Visual Space 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 Associative 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 Alexia
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

51. Visual Imagery
Neural structures mediating perception and visualization are not completely independent
Right hemisphere superiority in mental rotation
Evidence that the left temporal-occipital region is responsible for image generation

52. Snapshot: Generating Mental Images
Mark D’Esposito and colleagues
What is the neural basis for visual imagery?
fMRI study
Found that visualization of concrete words increases activation in the left posterior temporal-occipital region
Findings consistent with other imaging studies and case studies