Week 1: Chapter 13 - The Occipital Lobes Flashcards
What is the primary function of the occipital lobe?
It serves as the brain’s main center for vision, shaping perception, guiding movement, and influencing behavior.
Where is the occipital lobe located?
At the posterior pole of the cerebral hemispheres, beneath the occipital bone.
What structure separates the occipital lobe from the parietal lobe?
The parietal-occipital sulcus.
Why is the boundary of the occipital lobe uncertain?
There are no clear landmarks separating it from the temporal and parietal cortices.
What is the calcarine sulcus?
A prominent structure housing much of the primary visual cortex (V1) and dividing the upper and lower visual fields.
What does the lingual gyrus contain?
Parts of visual areas V2 and VP.
What is the role of the fusiform gyrus?
It houses area V4 and is crucial for processing color and complex shapes.
What are the three key anatomical features of the visual cortex?
Calcarine sulcus, lingual gyrus, and fusiform gyrus.
What was the old model of visual processing?
A strict hierarchical model moving linearly from V1 to V2 to V3.
What is the current model of visual processing?
A distributed hierarchical model with parallel and interconnected pathways.
What is the function of V1?
Receives input from the LGN and sends projections to all other occipital areas.
How is V2 connected in the visual cortex?
It connects to all other occipital regions.
What happens after processing in V2?
Three parallel pathways emerge to the parietal cortex, superior temporal sulcus (STS), and inferior temporal cortex.
What is the function of the dorsal stream?
It is involved in visually guided movement and projects to the parietal cortex.
What is the function of the ventral stream?
It handles object recognition and projects to the inferior temporal and STS pathways.
What does the ventral stream process?
Color, faces, and motion perception.
Why is the modern visual processing framework considered non-linear?
Because it involves multiple, interactive pathways for complex perception and movement coordination.
What visual functions are processed in V1 and V2?
Color, form, and motion.
Which area processes color and receives input from V1’s blob areas?
V4.
What does V5 (MT) specialize in?
Motion detection.
Which area processes dynamic form (shape of moving objects)?
V3.
What happens when V4 is damaged?
Complete color blindness, including loss of color imagination and memory.
What are the effects of V5 damage?
Inability to perceive motion; objects vanish when moving.
What results from V3 damage?
Form perception deficits, though total loss requires V3 and V4 damage.
What happens when V1 is damaged?
Cortical blindness, but some unconscious visual processing remains (blindsight).
Which area might allow limited visual awareness despite V1 damage?
V3.
Which brain lobes are involved in extended visual processing?
Parietal, temporal, and frontal lobes.
What is the FFA responsible for?
Face perception.
What is the PPA specialized for?
Scene layout and appearance.
What does the STSp process?
Moving bodies.
What did Andrews et al. (2002) demonstrate about the FFA?
FFA responds more strongly when faces are perceived in ambiguous images like Rubin’s vase.
What are LIP and AIP/PRR involved in?
Eye movements and object-directed grasping, respectively.
What is vision for action?
Visual guidance for specific movements, like reaching or catching.
What is action for vision?
Active visual scanning of relevant features, such as eyes and mouth on a face.
What is visual recognition?
Identification and categorization of objects, symbols, and faces.
What is visual space?
Organizing visual information into egocentric and allocentric maps.
What is visual attention?
Filtering and focusing on relevant stimuli, like text on a page.
What is egocentric space?
Object location relative to oneself, used for movement control.
What is allocentric space?
Object location relative to other objects, used in spatial memory.
What are the two primary visual streams identified by Milner and Goodale?
Dorsal stream for action and ventral stream for object recognition.
What did patient studies by Milner and Goodale reveal?
Dorsal damage impairs action, ventral damage impairs recognition.
What activates posterior parietal neurons?
Movement toward a visual object.
How many visual pathways connect V1 to the parietal cortex?
Three, each coding different movement-related visual aspects.
What are symptoms of parietal cortex lesions?
Visuomotor and visuospatial impairments.
What is the function of the STS stream?
Integrates visual, auditory, and somatosensory input and processes biological motion.
Where does the STS stream originate?
Both parietal and temporal pathways.
What did Haxby’s PET studies show?
Face matching activates the temporal lobe, spatial tasks activate the parietal cortex.
Which area is linked to motion detection?
V5.
Which areas are activated for shape recognition?
Superior temporal sulcus (STS) and ventral temporal lobe.
Which area processes color perception?
V4 in the lingual gyrus.
What role does the prefrontal cortex play in visual processing?
It generates top-down predictions to speed up perception.
What is an example of top-down visual prediction?
A baseball player anticipating a pitch using experience.
Where do top-down predictions originate?
Prefrontal cortex.
How do top-down and bottom-up processes interact?
Top-down memory-based predictions combine with real-time sensory input.
How does visual information from the retina project to the brain?
Left retina halves project to the right brain, and right retina halves to the left.
What indicates damage outside the brain in vision loss?
Visual disturbance in only one eye.
What happens with damage to a specific V1 region?
Loss of vision in a specific part of the visual world.
What is monocular blindness?
Loss of sight in one eye due to retina or optic nerve damage.
What is bitemporal hemianopia?
Loss of both temporal visual fields due to a lesion in the medial optic chiasm.
What is nasal hemianopia?
Loss of one nasal visual field from a lateral chiasm lesion.
What is homonymous hemianopia?
Blindness in one entire visual field from cuts in the optic tract, LGN, or V1.
What is quadrantanopia?
Loss of vision in one-quarter of the visual field.
What is macular sparing?
Preservation of central vision due to dual blood supply or bilateral foveal projection.
What is a scotoma?
A small blind spot caused by a small occipital lesion, often unnoticed.
What symptom did B.K. experience after V1 damage?
A left visual field scotoma with visual noise.
What does B.K.’s case suggest?
Visual processing functions like form, color, and motion are independent.
What is blindsight?
Unconscious visual processing despite cortical blindness.
What was special about G.Y.’s blindsight?
Some conscious awareness of motion with V5 and prefrontal activation.
What did J.I. lose after V4 damage?
Color perception, imagination, and memory.
What did P.B. retain despite visual impairment?
Conscious color perception, with intact V1 and V2 activation.
What condition did L.M. develop after V5 damage?
Akinetopsia — inability to perceive motion.
What did D.F.’s form agnosia reveal?
Ventral stream damage impaired recognition, but dorsal stream allowed action.
What condition did V.K. develop after parietal damage?
Optic ataxia — impaired visually guided grasping despite object recognition.
What does D.’s prosopagnosia suggest about hemispheric asymmetry?
Right occipito-temporal damage impairs face recognition.
What did T.’s alexia suggest?
Left occipito-temporal damage affects reading and color naming.
What conclusion comes from these case studies?
Visual functions are specialized, and perception is fragmented.
What is apperceptive agnosia?
Failure to form coherent percepts despite intact basic vision.
What is a typical symptom of apperceptive agnosia?
Simultagnosia — only one object perceived at a time.
What causes apperceptive agnosia?
Bilateral lateral occipital damage, often from carbon monoxide poisoning.
What is associative agnosia?
Inability to link visual percepts to stored knowledge.
Where is the lesion in associative agnosia?
Higher ventral stream, especially the anterior temporal lobe.
What is prosopagnosia?
Inability to recognize familiar faces.
Where is prosopagnosia typically localized?
Bilateral fusiform gyrus damage.
What is alexia?
Word blindness, or inability to read.
Which areas are affected in alexia?
Left fusiform and lingual gyri.
What is visuospatial agnosia?
Difficulty navigating environments and recognizing landmarks.
Where is visuospatial agnosia localized?
Right medial occipitotemporal region.
What do visual agnosias illustrate about perception?
That it’s made of distinct, specialized functions in the ventral stream.
