Seeing is believing

January 31, 2013 § Leave a comment

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Martin Blom is loading up his car outside a supermarket one evening when an unknown assailant shoots him in the back of the head. The bullet damages the occipital lobe in his brain, rendering him cortically blind. At night-time, however, Blom is convinced he still has the ability to see.

Blom is introduced to a man called Loots who rides a bicycle and works at a circus. Every time a bicycle goes past when he is on his night-time excursions, it is Loots –  doing handstands or juggling as he cycles. The nurse in Blom’s clinic sometimes comes up to his bed late in the evening and silently removes all her clothes… So begins Rupert Thomson‘s extraordinary novel The Insult.

Blom has Anton-Babinsky – or Anton’s – syndrome. What he actually ‘sees’ are his mind’s imaginings, prompted by the evidence of his other senses.

Most people who suffer from sight impairment caused by damage to the eyes still have some partial remnants of vision. They can often, for instance, make out large objects or differentiate between darkness and light.

When the primary areas of the occipital lobe are severely damaged, however, the brain is unable to process any visual information. The eyes may be working perfectly, but the blindness experienced by the sufferer when the visual cortex is removed or destroyed is total.

Like people who still experience feeling in an amputated limb, Anton’s syndrome is a form of anosognosia – a condition in which the mind refuses to accept the existence of a disability.

In this case, the brain creates a substitute visual reality that is so elaborate, complex and lucid the blind person is totally convinced they can see. Their confabulation, which leads them to behave and talk as though they were sighted, may be so complete that even those around them can fall under the illusion. It can be some time before doctors realise their patient is sightless, attention only being aroused when they walk into doors or collide with furniture.

Of course, as in Thomson’s book, what the patient imagines they can see may well be radically different to what is there in reality. The condition is possibly similar to what happens when people experience hallucinations, which can sometimes be caused by simple visual deprivation. Similarly, one theory of apparitions is that they are not external phenomena but caused by stimulus to certain areas of the brain – perhaps by electro-magnetic currents – which creates the illusion of an external image. This would explain why one person in a room might see a ‘ghost’ when another does not.

A converse but related condition to Anton’s syndrome is blindsight. This is the ability of the cortically blind to respond to visual stimulus even though their minds are incapable of processing visual information. Images or movement sensed by the eyes enable the person to see without consciously being aware of it. Some people who suffer from cortical blindness are able to walk down a corridor avoiding objects that have been placed in their path with no awareness that the objects are actually there. The brain is able to see even when the conscious mind cannot.

There seems to be no research into the relationship between the two conditions. In The Insult, Blom largely successfully manages to navigate his blindness (not as though it does him much good…). It made me wonder if blindsight and Anton’s syndrome can occur concurrently – if a person’s denial of blindness and their creation of an alternate visual reality could be validated by the brain’s ability to still perceive the world without being able to consciously interpret it.

Blindsight: seeing without knowing it
The Dreamlife of Rupert Thomson

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