Agnosia and Prosopagnosia

Question 1

what is agnosia

Answer 1

agnosia is when object recognition fails and typically occurs after damage to the occipital or inferior temporal cortex

Question 2

Apperceptive Agnosia: Mr S

Answer 2

• Able to move about and negotiate obstacles without difficulty
• Their grasp reveals knowledge of size and shape (Goodale & Milner,2004)
• Low-level binding of feature appears to be absent
• Unable to perform basic copying and matching tasks

Question 3

what is Apperceptive Agnosia

Answer 3

where a person has difficulty recognizing objects due to problems with perception. Even though their eyesight may be fine, they struggle to piece together visual information to understand what they’re looking at.

Question 4

where in the visual system model would damage resulting in apperceptive agnosia occur?

Answer 4

stage 2 : shape representation; can’t integrate local features

Question 5

Associative Agnosia: LH

Answer 5

• Copying and matching skills are unimpaired
• Patient unable to name the object despite intact knowledge
• Involves a failure in accessing knowledge about the objects
• But… apperceptive vs. associative is an oversimplification– there are many other “types” of agnosia

Question 6

where in the visual system model would damage resulting in associative agnosia occur

Answer 6

stage 3 = object representation

Question 7

what is prosopagnosia

Answer 7

Profound loss in ability to recognize faces usually due to a right inferotemporal lesion.

• Though unable to recognize previously familiar faces via visual input, recognition by other modalities remains intact. Thus, individuals can be identified by their voices.
• Note that the ability to recognize faces is tested through overt behavioral measures [essentially just asking ‘do you know who this is?’] .

Question 8

covert recognition

Answer 8

Peak skin conductance responses (SCRs) occur 1-5 seconds after a face has been presented (red arrows).

• Peak amplitudes are larger for a familiar relative to an unfamiliar face (Tranel et al., 1985).
• Similar patterns have been observed for prosopagnosic patients (Ellis et al., 1993)

Question 9

what is peak skin conductance

Answer 9

an objective, transient indication of autonomic nervous system arousal in response to a stimulus - [simply how sweaty you are…]

Question 10

Recognition without feeling: Capgras delusion

Answer 10

Patients with Capgras delusion both recognize a face and yet deny the identity of the individual. — a person believes that someone they know, has been replaced by an identical impostor. The person feels strongly convinced of this, even though there’s no evidence to support it.

covert= the person feels familiar to them

Question 11

difference between prosopagnosia and capgras delusion

Answer 11

so in prosopagnosia, the person subconsciously knows them but can’t recall them

but in capgras delusion, the person can recognise the person but they don’t feel familiar to them leading to the delusion of an imposter

covert= the person feels familiar to them

Question 12

normal route for face processing

Answer 12

**dorsal route **
1. visual cortex
2. STS
3. IPL
4. Cingulate gyrus
5. Hypothalamus
**Ventral route **
1. visual cortex
2. amygdala
3. hypothalamus

Question 13

what happens to the normal route for face processing in prosopagnosia

Answer 13

loss in the ventral stream

Question 14

what happens to the normal route for face processing in capgras delusion

Answer 14

loss in the dorsal stream