Balint's syndrome and hemispatial neglect

Question 1

Lesions on Temporal / Ventral Pathway - ‘what’ stream

Answer 1

Causes specific impairments in object recognition

Question 2

Lesions in Parietal / Dorsal Pathway - ‘where’ stream

Answer 2

Causes deficits in spatial attention

Question 3

Balint’s Syndrome - Treisman (1999) - Patient RM

Answer 3

• Two strokes damaging large areas of bilateral occipito-parietal cortex
• Was unable to focus attention on more than one object at a time (simultanagnosia)
  Particular problems combining features of a stimulus: made conjunction errors when seeing objects for 10 sec
  The parietal lobe (the “where” pathway) is important for feature binding

Question 4

Parietal Cortex + Feature Binding - Corbetta et al (1995)

Answer 4

During conjunction search,
posterior temporal cortex and
parietal cortex shows increased
activation over baseline control
conditions

Question 5

Parietal Cortex + Feature Binding - Walsh et al (1995)

Answer 5

TMS to parietal lobe disrupts conjunction search but not feature search

Question 6

Parietal Cortex + Feature Binding - Esterman et al. (2007)

Answer 6

Stimulation of intraparietal sulcus
reduces illusory conjunction

Question 6

What is Hemispatial Neglect

Answer 6

A lack of awareness of stimuli presented to the side of space
on the opposite side to the brain damage (contralesional)

Question 7

Symptoms of hemispatial neglect - Bisiach & Luzzatti, 1978

Answer 7

2 patients were asked to imagine + describe Piazza del duoma in Milan
- Both reported objects mainly on the spared side of space - representational neglect

Question 8

Extinction - Duncan et al, 1997

Answer 8

Patients detect a single stimulus presented to one visual field (typically left), but fail to detect the same stimulus when another stimulus is presented to the other field
– Suggests that visual attention isn’t unitary, but is a result of local competition between representations

Question 8

More symptoms of Hemispatial Neglect - Robertson, 2004

Answer 8

• Deficit to attend to information in contralesional space (for sensory information, info in mind’s eye + bodily space)
• Unilateral neglect is often object-based irrespective of object’s position in space - R-2004