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52 Cards in this Set
- Front
- Back
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What does the Magnocellular pathway project to that the Parvocellular structure doesnt?
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Superior Colliculus
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What are some differences between the M cells and P Cells?
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The M cells are larger, faster conducting, used to track movement in the visual field, project to the parietal lobe/dorsal pathway, and make up the bottom two layers in the LGN..
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How does the Ungerleider & Mishkin study represent a double dissociation?
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The monkeys with bilateral parietal lesions did fine on the object discrimination, but they did poorly on the landmark task. The monkeys with bilateral temporal lesions did poorly on the object task, but just fine on the landmark task. This is a double dissociation.
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What was the landmark task? What was the object discrimination task?
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The landmark task was just picking the well closest to the tower. The object discrimination task was just to identify which object they'd seen before.
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Why are there separate pathways for what and where?
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They each perform different functions in visual processing. They require different kinds of information, have different computational demands, and therefore have specialized machinery.
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What does acuity mean, and which cells have high acuity?
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It refers to the ability to resolve details; parvocells have good acuity.
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Which cells process color?
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Parv cells
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What are V4 and MT?
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They are extrastriate cortices. MT is the "where" part, V4 is the "what" part.
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Why were PET scans relevant to discovering these two pathways?
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Zeki and his colleagues found regions of the brain that were active only under color and only under motion.
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What is the other kind of evidence for the segregation of the two pathways?
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Lesion specific evidence for attribute specific deficits.
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What is akinetopsia?
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It is motion blindness. It was discovered by Zihl and his colleauges. The lesion locus is bilaterally along the dorsal pathway.
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What are visual agnosias NOT?
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They are not naming impairments. They are not memory impairments. They are not a deficit in elementary sensation. It goes beyond the notion of attributes, and builds up the notion of percepts.
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What are the three kinds of visual agnosias?
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Apperceptive, Integrative (intermediate) and Associative.
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What do apperceptive agnosics suffer from?
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Impaired shape identification, impaired copying, impaired matching, difficulty judging orientation explicitly. They can trace an image and they can accurately negotiate a path (see optical ataxia).
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What do associative agnosics suffer from?
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Impaired recognition of complicateed forms and objects. Theyre early visual processing is okay though. They're also helped a lot by context.
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What's the problem with integrative agnosics?
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They have a ton of difficulty forming a structural representation. They can't deal with integration and grouping, and they can't handle overlapping figures. They can copy, but it's very labored, and often incorrect.
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What does object constancy/object-centered view refer to?
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We can recognize objects despite shadows, obscuration, and varied angles.
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What is the stage model of visual recognition?
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Image --> Shape Coding --> Figure/ground Feature integration grouping --> mapping to structural description
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What are the gestalt grouping principles?
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Good continuation, closure, similarity, and proximity.
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Where is the recognition deficit for apperceptive agnosia?
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Early in the stage model -- shape coding site.
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Where is the recognition deficit for associative agnosia?
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Later deficit, probably inbetween mapping to structural description and semantic knowledge.
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Where is the recognition deficit for integrative agnosia?
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Probably inbetween grouping and mapping to structural description.
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What did Behrmann and his colleagues look at?
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They set up the task that required people to study objects and their parts in relation to each other, then distinguish between targets and foils.
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Who was case SM and what did he show?
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He failed on the behrmann study, indicated an inability to form a structural description.
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Why is case CK relevant?
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He (integrative agnosic) created a double dissociation with prosopagnosics because he could recognize faces made of fruit, but not objects.
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What did Yin do?
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He (she?) created the yin inversion task which showed that faces are processed as configural wholes -- implied a specialized configuration processor.
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What is the FFA?
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A bilateral region in the fusiform gyrus is activated when we look at faces
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What's the relevance of greebles?
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The greeble study showed that the fusiform face area can be "modified" to process things that are very familiar. Greeble experts showed activation in the FFA.
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What does the Lateral Occipital complex do?
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It's really involved in recognizing objects
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What does the Parahippocampal place area do?
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It's specialized for perceiving environmental scenes, buildings, and landmarks. Damage to this area affects the ability to learn/recognize new places and landmarks.
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What does domain-specificity refer to?
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It refers to things like places, faces, objects, and words. Recognition processors can operate independently and therefore become selectively impaired by damage.
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What did D.F. have?
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Apperceptive agnosia... damage to V2, V3, V4, and the ventral stream.
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What's up with the slits in wood?
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Apperceptive agnosics cannot identify orientation of the objects, but they can direct their hands through the slit.
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Dissociate orientation tasks for apperceptive agnosics:
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Their explicit orientation tasks are impaired, but their implicit orientation tasks are spared.
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What are the elements of Balint's syndrome? (4)
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Gaze apraxia, optic ataxia, spatial disorientation, and simultanagnosia.
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What causes balint's syndrome?
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Bilateral posterior parietal damage.
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Define ataxia:
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loss of coordinated movement.
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Define apraxia:
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disorder of skilled, voluntary movements
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What's spatial disorientation:
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it's the inability to appreicate spatial relations. depth perception impairement.
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What's simulatanagnosia?
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the inability to see more than one object at a time.
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Unilateral right parietal damage =
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Unilateral left neglect.
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What are some symptoms of right parietal damage?
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Left hemiparetic arm
Anosognosia: unawareness of limb/denial of illness Constructional apraxia Visual and tactile extinction to double simultaneous stimulation Could be in visual or tactile modality… Allesthesia: mislocalization of stimulation Rightward gaze deviation Left neglect |
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What is the difference between attributes and modalities?
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Modalities relate to a specific sense, but attributes are part of that sense. The two are not mutually exclusive either.
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What are some examples of neglect behaviors?
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They only react to speech and sounds from one side of space. They fail to recognize one's arm or leg as one's own. They act as though one side of space does not exist. ETc etc.
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What are the two classes of reference frames?
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Egocentric and allocentric space.
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What are two egocentric reference frames?
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The retinotopic and hemispatial reference frames.
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What are some allocentric reference frames?
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Environmental frames -- relative to gravity and cardinal directions;
Stimulus-Centered -- relative to the midline of the object. |
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What are three implications for the presence of two classes of reference frames?
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It implies that spatial relations are represented in a variety of reference frames, parietal cortex is the location of these frames, and different frames are used for different spatial processes.
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What did Bisiach do?
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Piazza square -- neglect is due to problem forming visual representations by the damaged hemisphere
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What is covert attention?
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When you attend to something that you aren't directly looking at.
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What did Posner do?
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He showed that neglect patients have a really hard time dealing with invalid cues -- can't dissociate from their overt attention.
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What did Kinsbourne think?
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He said that each hemisphere competes for attention, and when one hemisphere is damaged the other one dominates -- it over-attends in its preferred direction.
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