Week 3: From normality to pathology: the pitfalls of neuropsychological assessment [2]

Question 1

(Piazza del Duomo experiment - Bisach & Luzzati, 1978) What were patients asked to do in this experiment? what did this experiment demonstrate?

Answer 1

Double dissociation between representational and perceptual neglect
- patients asked to imagine being in a well-known square in milan and draw the buildings on either side.

Question 2

(Piazza del Duomo experiment - Bisach & Luzzati, 1978) - experimental findings?

Answer 2

• Patients could only copy the LHS of the picture (and neglect the other side)
• When patients asked to stand on other side of the square they then drew the other half of the buildings on the other side of the square!
• Patients HAD KNOWLEDGE in their memory of the square but couldn’t access this by imagery–> demonstrates DBL diss between representational and perceptual neglect.

Question 3

The brain + vectors for attention?

Answer 3

The brain has vectors for attention
One vector points attention to the LHS
One vector point attention to the RHS

Question 4

Attention & perception - relationship?

Answer 4

Attention is not controlled within the same module as Perception (explains dbl diss between perception and visual imagery)
The SPATIAL FRAMES OF REFERENCE we have are different for imagined and external space of the mind

Question 5

Tasks used to assess visuo-motor neglect

Answer 5

• copy / completion tasks
• line / letter cancellation
• horizontal line bisection task

Question 6

What unusual case demonstrated DBL DISS between perception and visual imagery?

Answer 6

Patient could DRAW ENTIRE IMAGE FROM MEMORY

But then when asked to copy image, ONLY COPIED HALF

Question 7

Importance of the parietal lobes - case study outline?

Answer 7

Patient had 2 strokes, 1 either side effecting each Parietal lobe.
Demonstrated PERCEPTIVE NEGLECT and VISUOSPATIAL at the same time

Question 8

How do the parietal lobes contribute to visual perception?

Answer 8

Mediate the visual field in a graded fashion –> lesion to the RHS will cause more severe neglect in the far left of the visual field, moderate in the middle left, and little to no effect in the near left visual field.

Question 9

Neglect is more severe in RHS lesion of pareital lobe - what does this suggest?

Answer 9

Suggests that direction of spatial attention is ASYMMETRIC and RH parietal lobe is more specialised for spatial attention

Question 10

(Beschin, Basso, Della Sala 2010) - Perceiving left and imagining right - outline case study

Answer 10

• left parieto-occipital haemorrhage AND
• right thalamic stroke
• showed severe right personal neglect (e.g. touching own body parts)
• right perceptual neglect in tasks with (e.g. cancelling tasks) or without (e.g. description of a complex picture) motor response.
• He had also right-sided neglect dyslexia (including single words), without language impairments.
• the patient also presented with a clear left-sided deficit in the representational domain (e.g. imagery tasks).
• –> suggests dissociation between imagery and perception within the neglect syndrome.

Question 11

(Beschin, Basso, Della Sala 2010) - Perceiving left and imagining right —> What did the findings imply?

Answer 11

DBL DISS between imagery and perception within the neglect syndrome
Asymmetry in the neural networks utilised for imagery and perception

Question 12

(Beschin, Basso, Della Sala 2010) - Perceiving left and imagining right —> problem with study?

Answer 12

The patient had 2 lesions but couldn’t observe the impacts on the neural systems after the first lesion and then the second. Difficult to make very robust conclusions about what is causing neglect on each side:
“We saw the patient after he had had both the right
and the left stroke thus making it hard to draw final conclusions on the anatomical counterpart of the extraordinary dissociation he showed. Considering
also his clinical history (e.g., perceptual neglect observed by his wife soon after his left stroke), the attribution of the right perceptual and personal neglect to his left lesion and of the representational neglect to his right is a more conservative hypothesis”

Question 13

What can we conclude heterogeneous nature of neglect?

Answer 13

Different frames of attention may be operating for different types of perception –> reflective of the different ways objects are represented

Question 14

What can we conclude as a result of studies into neglect?

Answer 14

Due to ATTENTION not PERCEPTION
Not to be confused with low-level visual perception
Right inferior lobe is responsible