The Occipital Lobe Flashcards
What is the dorsal stream?
- The where/how stream
- Visual guidance of movements
What is the ventral stream?
- The what stream
- Object perception (including colour)
What are the five categories of vision?
- Vision for action (parietal visual areas in dorsal stream; reaching, ducking, catching)
- Action for vision (visual scanning, eye movements and selective attention)
- Visual recognition (temporal lobes; object recognition)
- Visual space (parietal and temporal lobes; spatial location)
- Visual attention (selective attention)
What is monocular blindness?
- Loss of vision in one eye
- Results from destruction of retina or optic nerve
What is bitemporal hemianopia?
- Loss of vision from both temporal fields (lateral vision)
- Results from lesion to medial region of the optic chiasm
What is nasal hemianopia?
- Loss of vision of one nasal field
- Results from lesion of the lateral chiasm
What is homonymous hemianopia?
- Blindness of one entire visual field
- Results from a complete cut of the optic tract
- Damage to LGN or V1
What is macular sparing?
- Results from lesion to occipital lobe
- Sparing of central or macular region of visual field
- Differentiates lesions of optic tract or thalamus from cortical lesions
- Macular sparing occurs only after lesions to the visual cortex
What is quadrantanopia of hemianopia?
- Results from lesion to the occipital lobe
- Complete loss of vision of one-quarter or one-half of the fovea
What are field defects?
- Scotomas - small blind spots
- Results from small lesions to occipital lobe
- Visual system is good at overcoming these blind spots
What is blindsight?
-Perception of motion and location without perceiving content
What is visual form agnosia?
- Inability to recognize line drawings of objects
- Bilateral damage to LO region and tissue between parietal and occipital lobes
What is optic ataxia?
- Deficit in visually guided hand movements
- Bilateral hemorrhages in occipito-parietal regions
Prosopagnosia is caused by a lesion in which brain area?
-Right occipito-temporal lesion
Alexia is caused by a lesion in which brain area?
-Left occipito-temporal lesion
What is apperceptive agnosia?
- Deficit in ability to develop percept of an object of objects
- Can describe components of object but cannot say what the whole thing is
- Bilateral damage to lateral parts of occipital lobes
What is simultagnosia?
-Unable to perceive more than one object at a time
What is associative agnosia?
- Can perceive objects, but cannot identify them
- No memory of objects
- Lesions to anterior temporal lobes
Damage to what area causes alexia? What agnosias is alexia a form of?
- Damage to left fusiform and lingual areas
- Form of object agnosia (inability to construct perceptual wholes from parts) OR
- Form of associative agnosia (word memory is damaged or inaccessible)
