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Bryan Kolb & Ian Q. Whishaw’s. Fundamentals of Human Neuropsychology, Sixth Edition Chapter 13 Lecture PPT. Prepared by Gina Mollet, Adams State College . The Occipital Lobes. Portrait: An Injured Soldier’s Visual World. P.M. Struck by a bullet in the back of his brain

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slide1

Bryan Kolb & Ian Q. Whishaw’s

Fundamentals of

Human Neuropsychology,

Sixth Edition

Chapter 13

Lecture PPT

Prepared by Gina Mollet, Adams State College

portrait an injured soldier s visual world
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
anatomy of the occipital lobes
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
subdivisions of the occipital cortex
Subdivisions of the Occipital Cortex
  • Map based on monkey occipital cortex
subdivisions of the occipital cortex1
Subdivisions of the Occipital Cortex
  • Roger Tootell
    • Map of human cortex
subdivisions of the occipital cortex2
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
subdivisions of the occipital cortex3
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
connections of the visual cortex
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
visual pathways
Visual Pathways
  • Dorsal Stream
    • Visual Guidance of Movements
  • Ventral Stream
    • Object Perception
  • STS
    • Visuospatial functions
a theory of occipital lobe function
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
visual functions beyond the occipital lobe
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
five categories of vision
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
categories of vision
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)
categories of vision1
Categories of Vision
  • Visual Attention
    • Selective attention for specific visual input
    • Parietal lobes guide movements and temporal lobes help in object recognition
visual pathways beyond the occipital lobe
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
visual pathways beyond the occipital lobe1
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
imaging studies of dorsal and ventral streams
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
disorders of visual pathways
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
disorders of visual pathways1
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
disorders of visual pathways2
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
disorders of cortical function
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
disorders of cortical function1
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
disorders of cortical function2
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
disorders of cortical function3
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
disorders of cortical function4
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
disorders of cortical function5
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
disorders of cortical function6
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
disorders of cortical function7
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
conclusions from case studies
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
visual agnosia
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
visual agnosia1
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
visual imagery
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
snapshot generating mental images
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