Flashcards in Ventral and Dorsal Stream (M2) Deck (40)
What is the spatial location system that is where things are relative to the head? 1. What area of the brain is this? 2
1. head-centered coordinate system
2. dorsal stream
What is the location of the lesion in a pure alexia? 1. What does it disconnect? 2
1. left hemisphere lesion, often left occipital and/or adjacent splenium
2. disconnect occipital cortex from posterior language areas (esp. left angular gyrus)
For a person with appreceptive agnosia, what are the things that she could NOT recognize or do?
1. identify grating orientation
2. recognize letters and numerals visually
3. recognize line drawings of common objects, including ones she had drawn herself
What stream is responsible for mental rotation of letters?
What is spared in pure alexia?
1. ability to write
2. ability to understand spoken language
3. ability to read letter-by-letter
4. ability to recognize and interpret pictures
Are object agnosia patients able to draw an object from memory? 1. Copy an object? 2
What is the inability to recognize faces called?
What stream is responsible for passive letter viewing?
What is the roles of V4 in visual perception?
1. some color perception
2. object perception (non-sophisticated)
3. gateway to higher ventral stream locations
What type of functions does the ventral stream contain?
1. pattern recognition
2. scrutiny of fine detail
What is the condition that is due to deafferentation of the ventral system? 1. What are they unable to do? 2. What is usually the cause of this? 3
1. appreceptive agnosia
2. to form a coherent percept of a stimulus
3. anoxia from carbon monoxide poisoning
What is the spatial location system that is where the world is relative to the eye? 1. What area of the brain is this? 2
1. oculocentric coordinate system
2. superior colliculus
What are the major ways that motion is important to aspects of visual perception?
1. figure/ground segregation (camo)
2. perception of 3D space
3. perception of 3D scene (induced motion)
4. perception of self-motion (train)
5. perception of change (time-lapse photo)
What are the areas of the brain that respond better when viewing "nonsense object" than "noise"?
1. lateral occipital cortex
3. inferotemporal cortex
What is the inability to read words in the presence of intact letter recognition and intact writing?
What is the spatial location system that is where things are relative to each other? 1. What area of the brain is this? 2
1. allocentric coordinate system
2. ventral stream
What is the pathway of the ventral stream? 1. What type of cells are these mostly? 2
1. V1 to V4 to infero-temporal cortex
What is spared in prosopagnosia?
1. recognition of common objects
2. recognition of one's own handwriting
3. able to copy pictures
What are the major locations that the retina projects to?
1. dorsal LGN of the thalamus
2. pulvinar of the thalamus
3. superior colliculus of the optic tectum
What are the areas of the brain that respond better when naming "tools" than when viewing "nonsense"?
1. inferotemporal cortex
2. left pre-motor area
What do the cells in the MT of the brain respond to?
perceived direction of stimulus motion
For a person with appreceptive agnosia, what are their results from the "posting" experiment?
1. could not identify or match orientation of slot
2. could place card into slot smoothly and normally
What major higher ventral stream locations does V4 project to?
1. inferotemporal cortex pattern recognition area
2. fusiform face area
3. parahippocampal place area
4. wordform area
What is the pathway of the dorsal stream? 1. What type of cells are these mostly? 2
1. V1 to MT/V5 to posterior parietal cortex
Which stream has the ability to attract your attention away from what is happening with the other stream?
dorsal takes attention from ventral
How are the cells of the MT organized?
in motion opponent fashion
What is the spatial location system that is where things are relative to the body? 1. What area of the brain is this? 2
1. egocentric coordinate system
2. dorsal stream
For parvo cells, what is their temporal ability? 1. Spatial ability? 2. Color ability? 3. Visual field area? 4
1. sluggish and sustained
2. all visible spatial frequencies (including high)
3. color opponent and luminance channels
4. mostly central
What is the primary circuit for extracting motion information from the stimulus?
Where is the lesion located in object agnosia?
shape area of brain
Is the ability to recognize faces hereditary or developmental?
What is often the cause of a pure alexia?
infarct to the left posterior cerebral artery
What type of functions does the dorsal stream contain?
1. perception of motion
2. guidance of motor behavior
3. attracting attention for closer scrutiny
If a patient has object agnosia, what other associative agnosias will they have (and which brain hemisphere is this located in)?
1. pure alexia (left hemisphere) and/or
2. prosopagnosia (right hemisphere)
For magno cells, what is their temporal ability? 1. Spatial ability? 2. Color ability? 3. Visual field area? 4
1. brisk and transient
2. mostly low frequency
3. only luminance
4. mostly peripheral
For a person with appreceptive agnosia, what are the things that she could do involving there visuomotor capabilities?
1. reach and grasp common objects easily and well (egocentric)
2. catch a ball thrown towards her (egocentric)
3. walk around obstacles in the environment (egocentric)
4. follow a light with her eyes (oculocentric)
For a person with appreceptive agnosia, what are the things that she could recognize or do?
1. recognize letters and numeral by touch
2. recognize common objects by touch
3. write letters and numerals from dictation
4. draw objects from memory
What is the inability to recognize objects in the presence of intact ability to detect them and their features?
What does damage to the ventral system disturb?
1. object recognition
2. visual memory
3. relationship between objects (allocentric coordinate system)