Spare me, Mr Rubbish Bin! Menaced by Imaginary Street Furniture

Night time with moon alone foot traveller walks down a wet and lonely road with leafless trees and stome walls on either side. in the middle distance a large old-fashioned house with tall chimneys has one set of windows lit.

November by J A Grimshaw (1836-1893)

In his book Hallucinations Oliver Sacks writes of a man Gordon H. who had a stroke and lost left peripheral vision in both eyes – left hemianopia. But he had

“…little awareness of his vision loss, as his brain appears to fill in the missing part. Interestingly, though, his visual hallucinations always seem to be context-sensitive, or consistent. In other words, if he is walking in a rural setting, he can be aware of bushes and trees and distant buildings in his left visual field, which when [he looks at them with his right side] are not really there.”

Sack’s correspondent, Gordon H.’s son, goes on to describe how in the kitchen his father would see the whole of a work surface and even illusory objects on it, which of course vanished when he tried to inspect them more carefully with his good side.

My first reaction on reading this is that my experience is quite different. True, when walking along a lane I see, or imagine I do, vegetation, houses, walls etc. in what is actual my blind region. My brain is filling in these features. But they correspond to real objects, ones I noticed earlier from further off, when they were still in my visual field. So what I am imagining is not the existence of the objects but the fact that I can see them at that moment. My brain is evidently using recent memory to help with the completion process.

I certainly don’t see imaginary objects on a table top, even when I’ve seen their real-life counterparts just a moment ago. I frequently spend minutes trying to locate an object I have put down somewhere. I don’t know if there is a special term for this condition (other than “visual search problems”) but it is recognized problem for those with visual field loss and there is at least one online therapy, Eye-Search, which can help some people.

But wait a minute! My experience is not so different the man Sacks writes about after all. Thinking more carefully I realize that I do sometimes see objects that aren’t there, in both an outdoor and domestic setting, and especially at night. But they are always things that might be a danger. For example in the street I imagine street lights that I might collide with, or branches that might scratch me. Indoors I imagine that my anglepoise lamp is in my way and about to jab into me. These momentary visions are always on my right, in the area where I have vision loss, and they cause me to start and flinch away, until I have checked they are not really there.

So it looks as though my brain is somehow selective about what it fills in and only works hard to invent objects that might be a threat. Perhaps this arises from some kind of instinctive over-caution, a sort defense mechanism in case something dangerous is really there. But I don’t imagine bloodthirsty robbers or snarling wolves, only inanimate objects like rubbish bins. So I don’t know. It’s intriguing.

Credit
Grimshaw painting http://commons.wikimedia.org/wiki/File:Grimshaw_-_November,_1879.jpg

Advertisements

About partialinsight

One evening I had a stroke. Half my sight vanished overnight. Adapting made me grasp how amazing the visual system and brain are. It also taught me to understand disability completely differently and I'm grateful for the lesson.
This entry was posted in Uncategorized and tagged , , , , , , , , , , , , , , , . Bookmark the permalink.

2 Responses to Spare me, Mr Rubbish Bin! Menaced by Imaginary Street Furniture

  1. The other day I was reading on Kinle. When I we t to peel potatoes their skins were covered in very legible words. Was this an hallucination or optic memory.

  2. Oh that’s very interesting indeed and set me thinking. If what we see corresponds to something real how can it be classed as an hallucination?

    Here’s something I just found out. It takes about a tenth of a second for anything we see to me transmitted to the brain and processed. So you could say we are always looking into the past. But if an object is moving, what we perceive is not what our eyes tell us. The brain fills in again, by showing us the object moved on a bit. I fibd that amazing.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s