Zusammenfassung der Ressource
Occipital Lobes
- Subdivisions
- Area V1
- Laminar organization most
distinct of all cortical areas
- Striate cortex
- Also visual cortex - striate
= striped appearance
- Color vision
- Primary job of V4, but
distributed through the
occipital cortex
- Connections of the visual cortex
- 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
- Dorsal stream
- Visual guidance
of movements
- Ventral stream
- Object perception
- STS
- Visuospatial functions
(body oriented)
- A theory of occipital lobe function
- Vision begins in V1 that is
heterogenous, and then travels to
more specialized cortical zones
- Selective lesions up the
hierarchy produce specific
visual deficits
- Visual functions beyond
the occipital lobe
- Vision related areas in the brain
make up 55% of the total cortex
- Multiple visual regions in the
temporal, parietal and frontal lobes
- Vision
- Not unitary, composed of many
specific forms of processing
- Vision for action
- Parietal visual areas
in the dorsal stream
- Reaching, ducking and catching
- 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)
- 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
- Homohemianopia
- 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
- Quadrantoanopia/hemianopia
- Complete loss of vision in 1/4 of
the fovea or in 1/2 of the fovea.
- Results from a lesion to the occipital lobe
- Visual agnosia
- Object agnosia
- Apperceptive agnosia
- Deficit in the ability to
develop a percept of the
structure of an object
- 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
- Other agnosias
- Prosopagnosia
- Cannot recognize faces
- Can recognize facial features,
facial expressions and tell human
form from non human faces
- Alexia
- Inability to read
- Form of object agnosia
- Inability to construct
perceptual wholes from parts
- Form of associative agnosia
- Word memory is damaged or inaccessible
- Results from damage to
the left fusiform and
lingual areas
- Imaging studies of dorsal
and ventral streams
- Haxby and colleagues
- PET study
- Found activation for facial
stimuli in the temporal region
- Also activation during a
location task in the
posterior parietal regions
and frontal lobes
- Detection of motion activated V5
- Detection of shape activated STS
- Colour perception activated area V4
- Visual imagery
- RH superiority in mental rotation
- Left temporal-occipital region is
responsible for image generation