Disorders of Vision Flashcards
What is Hemiahopias?
Loss of vision to left/right side of fixation. Due to damage to the visual cortex
How was cortical blindness tested using patient GY?
GY was presented with an object in upper/lower part of his “blind” visual field. Asked to point to the “opposite” location. The findings demonstrated there are different levels at which visual information is processed.
What is:
a) auditory agnosia
b) somatosensory agnosia
c) visual agnosia
a) inability to recognise sounds
b) difficulty perceiving objects through tactile stimulation
c) deficit in processing objects, faces, words
What are the 3 types of visual agnosia?
a) apperceptive
b) associative
c) integrative
apperceptive - failure in recognition due to failure in perception
associative - perception occurs but recognition doesn’t
integrative - symptoms of the other 2 types but primary visual activities are intact
Who is patient IES?
Visual agnosia patient - Had a stroke and damaged ventral occipital lobes. Had colour blindness but did no t lose semantic knowledge or production problems. Was tested on object processing with
a) picture namings, 32.8% correct
b) real objects, 60% correct
Drawing from memory showed amazing stored knowledge and seemed to be intact
What task did they do with patient DF?
Post-card experiment
Matching task- turn card to match orientation of the slot (POOR PERCEPTION)
Posting task- reach out and post the card in the slot (GOOD ACTION)
What are the 2 visual processing streams and what pathway do they use?
1- Dorsal stream, involved in object localisation. Follows Retinotectal pathway to Posterior Parietal Cortex
2- Ventral system- Involved in object identification. Follows Geniculate pathway to infero-temporal cortex
Who is patient VK?
Could perceive objects but can’t interact with them. Good at planning movement but struggled to finally adjust. (Damage to posterior parietal lobe)
What did Muner and Goodale say about the ventral stream and dorsal stream?
Ventral stream - abstract representations of the world. Can be stored for future reference. Enables us to plan future actions.
Dorsal stream - Acts in real time. Guides actions and enables smooth movement.
