wk3: ND - Agnosia, Neglect, Dyslexia Flashcards
When are the 3 parallel pathways no longer segregated?
at the striate cortex
What does damage to the dorsal visual pathway lead to? (symptom)
impaired goal-directed “action” (dorsal is “where” pathway)
What does damage to the ventral visual pathway lead to? (symptom)
Agnosia (inability to perceive)
Can patients with visual agnosia see objects? Explain
yes, however even though they see the object, they don’t understand what it is
Can patients with visual agnosia copy drawings?
No, however they can draw from memory
Define optic ataxia
a high order deficit in reaching (i.e. reaching with their arms) visual goals that occurs with posterior parietal cortex (PPC) lesions. Is a problem with dorsal pathway
What is a classic test you can use to test for problems with dorsal stream (optic ataxia)?
Hold out an oval with a rectangular slit in it at arms length from the subject and ask them to extend their arm and match the orientation of the slit with their hand and spatially have their arm in the same spatial plane as the slit
How do patients with optic ataxia fair with orientation matching?
Generally not too much worse than normal. Not too many errors
How do patients with optic ataxia fare with spatial matching or “posting”?
Much worse. People with optic ataxia make more spatial errors
What is “posting”? in the context of the dorsal test in this lecture
posting = putting the card in the rectangular slit
How are parallel channels integrated into visual processing?
carry visual signals from retina into thalamus and thence into cortex (Magno-, parvo- and konio- cellular pathways)
Describe top-down feedback
modulation of afferent signals by processes such as attention
What is Functional Localisation?
Different attributes of each object being processed in different cortical areas; different modalities (e.g. sensory, cognitive) processed independently
What are the 3 parallel pathways from retina to primary visual cortex
Magnocellular
Parvocellular
Koniocellular
Name 4 other functions of the posterior parietal cortex
Central role in directing attention to spatial locations
Helps bind different attributes of an object together
Gating inputs into ventral stream
Important for reading? (dyslexia)
How can visual neglect occur?
via primary cortex damage. If this occurs, visual neglect will affect the contralateral visual field
True/False: Visual neglect leads to the same type of constructional disability
False