Lec 4-1 Flashcards
Visual perception v.s. visual-motor control
vis perception - recognize and identify objects and relations.
vis-motor control - control actions/movements
Describe blindsight, whats gone and what is still there
eyes are intact but have damage to visual cortex (V1) causes inability to consciously see and recognize objects.
can still avoid obstacles, grab objects, and grab moving object
ONLY REFERS TO V1 DAMAGE, DOESN’T REFER TO OTHER DAMAGE LIKE INF TEMP CORTEX.
Explain patient D.B’s blindsight
had visual cortex (V1) removed in right brain hemisphere, now can’t experience visual stimuli in left visual field
Explain what parts of the brain the left and right visual field go to
Left field - light enters eye and goes to the right side of the retina. Then goes to right hemisphere
Right field - light enters eye and goes to left side of retina, then goes to left hemisphere
so info from a hemisphere concerns both eyes (if you close an eye you will still see both hemispheres)
what are the two visual systems
what part of brain
cortical system - what (qualities and features of objects)
- inferior temporal cortex
midbrain system - where location and relation (relative to objects) of objects
- posterior parietal cortex
IS THIS ACCURATE STILL?
What does inferior temporal cortex do? Posterior parietal cortex?
what “stream” do they use
inf temp - object discrimination (what things are)
- ventral stream
post parietal - landmark discrimination (where things are/how system)
- dorsal stream
distinguish between Ungerleider & Mishkin’s idea of the two visual systems, and Milner & Goodale’s idea
Unger & mish - what v.s. where. Emphasize analysis of visual input
Milner & good - what vs how. Emphasize purpose of visual input (conscious perception vs visually guided action.
Describe patient “DF’s” condition
Suffered CO poisoning. Caused visual form agnosia (vision without form), = impaired form, shape, and size discrimination.
could still see colour and texture.
E.g. could see materials, colour, but couldn’t tell what the object is or orientation
opposite of RV
what is the significance of research on DF describe two studies done
Although she couldn’t see orientation, when asked to do motor actions, she could then orient things like to grab pencil or put card in slot.
Card in slot experiment.
- Asked to rotate the card to match the slot. couldn’t.
- then asked to put the card in the slot and was able to do it meaning she could orient it when carrying out the action.
Grip aperture experiments
- asked to reach for something and was able to open up her grip the right amount to grab the thing.
Based on DF’s symptoms, where what part of her brain was affected? What area was preserved
Areas associated with ventral stream damage (ventrolateral occipital cortex)
Areas associated with dorsal stream - visuomotor control preserved
Describe patients RV’s case
Had two strokes, damage in areas associated with dorsal stream (post parietal cortex)
- interrupted visual motor processing needed for visually guided action
- ventral stream still intact (object recognition)
- could recognize objects but suffered from optic ataxia
Opposite of DF
Describe the path that the ventral and dorsal streams take from the lecture diagrams
Image starts at retina
Then splits to superior colliculus and Lateral geniculate nucleus (LGNd)
Sup colliculus - unconscious midbrain structure, control eye movement reflexes (saccades). Leads to pulvinar
- Pulvinar - another unconscious eye part. Leads to posterior parietal cortex
- Posterior parietal cortex - conscious perception of where/how system.
(LGNd) - relay info like motion and colour and other qualities and features of objects along with spatial relationships of objects from midbrain to primary visual cortex (v1). From there it splits to posterior parietal cortex and inferior temporal cortex
- post parietal - where/how system
- inf temp - what system
Describe Balint’s syndrome
posterior parietal cortex damage - cause:
Spatial neglect of things in one side e.g. only comb left side of hair
Simultanagnosia - only able to perceive one object at a time e.g. describe left side of room only
Optic ataxia - inability to reach for objects especially in peripheral vision.
contrast RV and DF performance in a tests (2)
Test where they had to identify which stones are same and different, then test where they had to pick them up through the centre line.
- RV did better at identification (because had intact inf temporal - ventral stream)
- DF did better at pickup up task (because had intact post parietal - dorsal stream)
Test where have to insert card to slot
- RV better at orienting card
- DF better at inserting card
Compare Visual agnosia with optic ataxia regarding how each affects perception of objects and actions.
Which site is affected with each
visual agnosia
- can’t recognize objects
- perception affected but action is okay
- ventral path damaged
optic ataxia
- inability to reach for objects
- action affected but perception is intact
- dorsal path damaged
