Lecture 6 - Agnosia Flashcards
What are the two categories Of agnosia?
Associative and apperceptive
Define associative agnosia
Impaired object recognition
Inability to relate the percept as a whole to related stored semantic memories .
Normally related to a specific category like familiar faces
Where is the damage for associative agnosia ?
Damage to the grey and white matter in the occipitotemporal cortex
What is a case study example of someone with associative agnosia ? Who studied them?
Moscovitch (1997)
Define apperceptive agnosia
Impaired shape perception, can perceive local or basic features of a bigger picture
Struggle to group local features into global precepts e.g. Lines and colours onto shapes
Can’t produce a complete percept
What is the damage required for apperceptive agnosia?
Results from diffuse damage
What’s an example case study of someone with apperceptive agnosia? Who studied them?
Case DF
Milner (1991)
Which stream is involved in the processing of objects?
Ventral stream or the what pathway
What kind of features are processed early in the ventral stream as compared to later on?
Early on you have small receptive fields and neurons code for simple lines, followed by edges and corners and gradually the fields increase in size and you code for basic objects and faces.
What could CK do? And what was impaired?
Severely impaired object and letter recognition
Intact form perfection so they can see parts of the objects and recognise faces
If you showed a face made of fruit he would see the face but not the fruit
But if you showed just a fruit he would struggle to recognise it.
Also if you inverted the face or displaced the top and bottom half at all his recognition is impaired.
What was impaired and spared in the case of DF?
Severe impairment of the perception of simple geometric forms, letters, words, objects and faces
Could recognise people through voice or hairstyle.
What is the double dissociation in this topic?
Between CK and DF. So between associative and apperceptive agnosia?
Between the two systems responsible for processing holistic faces which CK has and then the second one that uses the little bits of a face to build up a face. This is something CK doesn’t have
Who is mr s?
Mr s is a severe visual form agnosic who had object recognition difficulties , he couldn’t copy which would put him in apperceptive rather than associative agnosia.
Unable to distinguish between simple geometric shapes.
What is agnosia?
Impairment of recognition even when you have a relatively intact visual perception, memory and general function
