Cortical Structure and
Function
OCCIPITAL LOBE
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
•
•
•
Dorsal Stream
– Visual Guidance of Movements
Ventral Stream
– Object Perception
STS
– Visuospatial functions (bio movement)
Disorders of Visual Pathways
•
•
•
•
•
•
2. Monocular Blindness
– Loss of sight in one eye
– Results from destruction of the retina or optic
nerve
3. Bitemporal Hemianopia
– Loss of vision from both temporal fields
– Results from a lesion to the optic chiasm
4. Nasal Hemianopia
– Loss of vision of one nasal field
– Results from a lesion of the lateral chiasm
5. Homonymous Hemianopia
– Blindness of one entire visual field
– Results from a complete cut of the optic tract,
LGN or V1
7. Macular sparing
– Sparing of the central or macular region of the
visual field
– Results from a lesion to the occipital lobe
6. 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
Disorders of Visual Pathways
•
Field Defects
– Scotomas - small blind spots
– Results from small lesions to the
occipital lobe
Visual Agnosia
• Object Agnosia
– Apperceptive Agnosia
• Deficit in the ability to develop a percept of the
structure of an object or objects (still see color,
motion, acuity)
• 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 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
Neuropsychological Tasks
seemingly linked to Occipital lobe
•
Benton task of Facial Recognition
– Fusiform gyrus (temporal lobe)
•
Hooper Visual Organization Test (VOT)
– Dorsal stream (parietal lobe)
•
Visual Motor Integration (VMI)
– Dorsal stream (parietal lobe)
•
Test of Visual-Perceptual Skills (TVPS)
– Not sure what region it tests and poor normative data
•
Visual Neglect (Bells Test)
– Simultagnosia (occipital) or contralateral neglect (parietal)?
•
Wide Range Assessment of Visual Motor Abilities (WRAVMA)
– No links to brain structures
•
Embedded Figures Task (EFT)
– No links to brain structures
Benton Face Recognition
• History: “facial agnosia”/ prosopagnosia
• Purpose: Measures visualoperceptual discrimination of unfamiliar
faces (not recognition/memory)
• Associated with right hemisphere: parietal, occipitoparietal and
occipitotemporal
• 3 parts:
– Match identical front view
– Match front view with ¾ view
– Match front view with various lighting conditions
Hooper
Visual Organization Test (VOT)
• Test of the ability to conceptually rearrange
disarranged pictures
• Posterior parietal lobe (dorsal visual stream)
• 30 items, total # correct
Answers at end of Occipital Lobe section
Visual Motor Integration (VMI)
• 3 parts: VMI, Visual Perception, Motor Coordination.
• VMI: Copy a developmental sequence of geometric
forms
• Visual Perception: ID the exact match for as many of the
27 stimuli as possible in 3 minutes.
• Motor: Trace the stimulus forms with a pencil without
going outside double-lined paths in 5 min.
Test of Visual-Perceptual
Skills (TVPS)
Visual-spatial
relationships
Using 7 subtests, in theory, assesses
visual processing of form, but limited data
Visual
discrimination
Visual closure
Visual form
constancy
Visual memory
(response
page)
Visual figure
ground
Visual
sequential
memory
(stimulus page)
Visual Neglect (Bells Test)
Visual Neglect (Bells Test)
Visual field defects and hemianopia impact performance minimally.
This is about right parietal lesions not the occipital lobe.
Wide Range Assessment of Visual
Motor Abilities (WRAVMA)
• Measure of visual motor, visual spatial and
fine motor skills
• 3 parts
– Drawing Test: Visual Motor Ability
– Matching Test: Visual Spatial ability
– Pegboard Test: Fine motor ability
Embedded Figures Task (EFT)
• Cognitive “style” measure
• Task= Find simple target shape within
complex design
•Scoring: Average time in seconds
•Higher score= greater difficulty
analyzing a parts separate from
whole/tendency to perceive complete
patterns instead of separate parts
Answers to Hooper
Visual Organization Test (VOT)
PARIETAL LOBE
The Parietal Lobes
• Postcentral Gyrus
– Brodmann’s areas 1,2, and 3
• Superior Parietal Lobule
– Brodmann’s areas 5 and 7
• Parietal Operculum
– Brodmann’s area 43
• Supramarginal Gyrus
– Brodmann’s area 40
• Angular Gyrus
– Brodmann’s area 39
Inferior Parietal Lobule
Use of Spatial Information
• Spatial information can be used :
– Object recognition
• Viewer centered object identification
– Determines the location, location orientation and motion of an
object
• Posterior parietal cortex
– Guidance of Movement
• Sensitive to eye movements
• Posterior parietal cortex
– Sensorimotor Transformation
• Neural calculations of the relative position of the body with
respect to sensory feedback from movements being made
and planned
Use of Spatial Information
• Spatial Navigation
– Cognitive spatial map
• Route knowledge, unconscious knowledge of how
to reach a destination
• Mental transformations are carried out by
the posterior parietal cortex
• Other functions of parietal lobes:
– Aspects of math
– Aspects of language
– Movement sequencing
Somatosensory Symptoms of
Parietal-Lobe Lesions
• Lesions to the postcentral gyrus produce:
– Abnormally high sensory thresholds
– Impaired position sense
– Deficits in stereognosis, or tactile perception
– Afferent paresis
• Clumsy finger movements due to lack of feedback
about finger position
Somatoperceptual Disorders
• Astereognosis
– Inability to recognize an object by touch
• Simultaneous Extinction
– Two stimuli are applied simultaneously to opposite
sides of the body
– A failure to report a stimulus on one side is referred to
as extinction
• Blind Touch
– Cannot feel stimuli, but can report their location
Somatoperceptual Disorders
• Agnosias
– Asomatognosia
• Loss of knowledge or sense of one’s own body
– Anosognosia
• Unawareness or denial of illness
– Anosodiaphoria
• Indifference to illness
– Asymbolia for pain
• Absence of normal reactions to pain
– Finger Agnosia
• Unable to point to the fingers or show them to the examiner
Symptoms of Posterior Parietal
Lobe Damage
• Contralateral Neglect
– Neglect for visual, auditory, and
somesthetic stimulation on one side
of the body or space
– Lesion most often in the right
inferior parietal lobe
• Right intraparietal sulcus and the
right angular gyrus
– Defective sensation or perception
– Defective attention or orientation
Left Parietal Symptoms
• Disturbed Language Function
• Apraxia
– Movement disorder in which the loss of movement is not caused
by weakness, inability to move, abnormal muscle tone,
intellectual deterioration, poor comprehension, or other disorders
of movement
• Dyscalculia
– Difficulties with arithmetic
• Poor recall
• Inability to discriminate left from right
• Right hemianopia
Apraxia and the Parietal Lobe
• Ideomotor Apraxia
– Cannot copy serial movements
– More likely to be associated with left parietal
lesions
• Constructional Apraxia
– Cannot copy pictures, build puzzles, or copy a
series of facial movements
– Associated with right and left parietal lesions
Symptoms of Posterior Parietal
Lobe Damage
• Deficits in drawing appear after damage to
the right parietal lobe
• Spatial Attention
– Function of the parietal lobe to selectively
attend to different stimuli
– Disengagement
• Shifting attention from one stimulus to the next
Disorders of Spatial Cognition
• Mental rotation requires:
– Mental imaging of the stimulus
– Manipulation of the image
• Left hemisphere deficit associated with the
inability to generate the image
• Right hemisphere deficit associated with
the inability to manipulate the image
• Inability to use topographic information is
associated with right hemisphere damage
Major Symptoms
Neuropsychological Tasks
linked to Parietal lobe
• Two Point Discrimination
• Seguin-Goddard Form Board/Tactual
Performance Test
• Line bisection
• Incomplete Figures
• Mooney Closure
• Right-left differentiation
Two point discrimination
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•
•
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Sharp, two point calipers
2.85 cm, 2.7, 2.54….
At each distance, touch either 1 or 2 points
2 1 1 2 1 1 1 2 2 2, 1 2 1 1 1 1 2 2 2 2, etc
Examinee indicates one or 2 touches.
Linked to contralateral postcentral gyrus
(BA1, 2, & 3).
Seguin-Goddard Form
Board/Tactual Performance
Test
• Formboard, pieces, blindfold
• Repeat for left, right, and both hands
• Total time to place pieces in formboard for
each trial.
• Remove formboard, provide paper
• Examinee draws formboard and places
the shape in the outline of the formboard.
• Contralateral parietal lesions (PE, PF) for
tactile and PG for drawing part
Line bisection
• Mark the middle of
each line.
• Contralateral neglect
• With right parietal
lesion, the lines to the
left side of the page
would be left blank.
Incomplete Figures/
Mooney Closure
• Label the object
• Right parietotemporal
junction (ventral
stream)
Right-left
differentiation
• Left parietal
lesions
Answers to
Incomplete Figures Test
Answers to
Incomplete Figures Test