Balint's syndrome

From Psy3241

Revision as of 21:37, 24 April 2008

What is Balint’s Syndrome?

Rezso (Rudolf) Balint identified Balint’s syndrome in 1909 as a disjointed and paralysis

of gazing ability with haphazard scanning skills. Balint’s syndrome is characterized by

optic ataxia (uncoordinated hand and eye movement) and optic apraxia (inability to

voluntarily guide eye movements and change locations of visual fixations). Due to the

combination of optic ataxia and optic apraxia, patients with Balint’s syndrome also

display simultanagnosia or the inability to perceive more then one object at a time even

when the objects are taking up the same area of the visual field. In some cases, the patient

may behave as if they are blind.

Simultanagnosia in Balint's Syndrome

What is really interesting about Balint’s syndrome is that the simultanagnosia involved

with Balint’s syndrome is not specific to one object or spatial location. For example, the

tester could hold up two objects that intersect each other on the patient’s visual field and

ask the patient what he sees. The patient is just as likely to pick one item over the other,

while being completely blind to the second object.

Jackson et al (2006) conducted perceptual priming tasks with a Balint's patient where 2

pictures were shown (either the same or different semantic categories), and the participant was

asked to either classify one of the pictures or name both pictures. The results indicate that

there was a significant decrease in classification performance when the 2 pictures were different

in semantic category. The surprising aspect of this result is that the patient rarely indicated

that he saw more than one object. Thus, Jackson et al (2006) found results pointing to a

theory that Balint’s patients do not have a difficulty in seeing more than one item at a

time, but they have a deficit in explicitly identifying one item at any given time.

They suggest that this could be from an inability to disengage attention from one object once

that object catches the patient's attention. When given more time, the patient with Balint’s

syndrome can sometimes identify more than one stimulus when asked.

A patient with Balint’s Syndrome, J.J., made significantly more classification errors when items

were presented sequentially in time instead of at the same time. This indicates that the priming

stimulus could have less of an influence when it is presented simultaneously with the probe item

than when it comes before the probe item. (Jackson et al, 2006)

It could be that there is a reduced amount of competition between items on a sequential

presentation in patients with Balint’s syndrome simply because when the stimuli are presented

simultaneously, the patient only consciously perceives one item instead of two, eliminating

competition between stimuli. (Jackson et al, 2006)

Brain Areas Involved

Balint’s syndrome has been associated with bilateral damage to the posterior parietal

cortex with a primary cause of the syndrome being multiple strokes, Alzheimer’s,

intracranial tumors or brain injury. Only recently has Balint’s syndrome been associated

with damage to the parietal-occipital vascular boarder zone and in children.

Refrences

Gillen, J.A. and Dutton, G.N. (2003). Balint's syndrome in a 10-year-old male. Developmental Medicine & Child Neurology, 45, (349-32).

From class discussions:

Jackson et al. (2006).dorsal simultanagnosia: An impairment of visual processing or visual awareness. Cortex. 42, 740-749.

Newport et al. (2006). The role of the posterior parietal lobe in prism adaptation: Failure to adapt to optical prisms in a patient with bilateral damage to posterior parietal cortex. Cortex. (2006) 42, 720-729.