week 5 - neglect/extinction

Question 1

Balints syndrome
patient RM - what damage

Answer 1

two strokes damaging large areas of bilateral occipito-parietal cortex

Question 2

Balints syndrome
patient RM - impairments

Answer 2

unable to focus attention on more than one thing at a time (simultagmosia)
particular problems combining features of a simulus
- made conjunction errors
- parietal lobe (where pathway) is important for this

Question 3

parietal cortex and feature binding

Answer 3

during conjunction search
posterior temporal cortex and parietal cortex show increased activation over baseline control conditions

1995: TMS to parietal lobe distrupts conjunction search but not feature search

2007: stimulation of intraparietal sulcus reduces illusory conjunctions

Question 4

hemispatial neglect
what?

Answer 4

a lack of awareness of stimuli presented to the side of space on the opposite side to the brain damage

(typically damage to the right parietial cortex therefore left vision distrupted)

Question 5

hemispatial neglect
symptoms - evidence

Answer 5

cancellation task
patients given a bunch of lines of a piece of paper
cross though lines they see

line bisection
have to draw a line in the middle of a line

copying
neglects left hand side when copying drawings

imagining
1978: report objects on the spared side of space

Question 6

hemispatial neglect
symptoms

Answer 6

deficit to attend to information in contralesional space
- external sensory info, representaional and bodily space

unilateral; neglect is often object based irrespective of the objects position in space
- They can see the objects on the left side BUT only the right half of them

Question 7

extinction

Answer 7

often found in. patients suffering from neglect but can occur independently

patients detect a single stimulus presented to one visual field but fail to detect the same stimulus when another stimulus is simultaneously presented to the other field

suggests that visual attention inst unitary but is a result of local competition between representations

Question 8

hemispatial neglect
how much is neglected?

Answer 8

2008: ERPs
early processing similar to healthy (V1, V2 ect)
large differences generated in dorsal perital lobe (where stream)

Question 9

hemispatial neglect
how much is processed?

Answer 9

1993: cannot accurately identify objects presented to the neglected field
50% chance of performance
therefore no conscious access of what they have seen

1993: priming stimuli
if word presented related to image participants faster at saying whether it is a real word or not
so meaning of neglected object must have been processed

Question 10

hemispatial neglect
lesions underlying neglect

Answer 10

right infrior parietal lobe

TMS on the same region produces neglect and extinction like symptoms in control participants (2000)

Question 11

what is neglect/extinction a defict of?

Answer 11

attention

2002: neglect mainly impairment of the stimulus driven system

Question 12

what exactly is impaired in neglect

Answer 12

posner cueing paradigm
1998: neglect patients benefit from valid endogenous cues in both visual fields

2001: experiment in which cue on the right (intact) field predicted stimulus on the left
patients benefict as much as healthy controls from valid cue

both suggest that endogenous orientating system is relatively intact in neglect patients

Question 13

disengagement of attention

Answer 13

2001

neglect patients most impaired when trying to disenagage attention from intact side

attented hemisphere exterts a hold signal

the invalid target should enage the exogenous system but it doesnt

Question 14

neglect/extinction: a summary

Answer 14

prevalence following right brain damage
- is attention lateralised in the brain

partucularly related to disengagement of the attentional spotlght from the ipsilesonal side of space

evidence suggests problems with exogenious attention disproportionately more than with endogenous attention