The Origin of Visions

Not too long ago, I posted a poem called “Esse Est Percipi” in this blog (It’s on the “Poems” page and a piece of the post “Thanksgiving Thoughts”). It is a poem about how I am coping with my vision loss. It turns out that it is really about how my brain is coping with vision loss. Just yesterday, I learned that what I am experiencing happens to about one-third of patients losing their vision. It is called Charles Bonnet Syndrome. A precursor to Darwin, Bonnet was an 18th century philosopher/naturalist who diagnosed the condition in his own grandfather.  Below is what I discovered in an article by Alan Wells at damninteresting.com about CBS. It is a fascinating “phantom limb”-like response to vision loss:

“Consider that each human eye normally receives data at a rate of about 8.75 megabits per second, a bandwidth which is significantly greater than most high-speed Internet connections. The visual cortex is the most massive system in the human brain, and it is packed with pathways which manipulate the rush of visual data before handing it over to the conscious mind. When disease begins to kink this firehose of information, a legion of neurons are left standing idle.”

Which means the brain compensates for the lack of visual data by creating it—a visual hallucination that appears very real but that I consciously know is not there. As you can see from my poem, “I am trying to make friends with what I see.” I also just learned that the course of Charles Bonnet Syndrome is between twelve and eighteen months. What started out as nausea and disorientation began to be less alarming and (occasionally) be amusing. It feels like my brain has gone too far and is providing illusions that flow through me in a dream-like sequence, sometimes common, sometimes comforting, sometimes still a little alarming. It has become experiential and now it may, just as quickly, be gone.

How much, I wonder, does the brain normally supply that is not part of what is objectively perceived? I read, in my research, that the brain fills in the blind spot of the optic nerve. How much more does it create?

“Human perception is patently imperfect, so even a normal brain must fabricate a fair amount of data to provide a complete sense of our surroundings. We humans are lucky that we have these fancy brains to chew up the fibrous chunks of reality and regurgitate it into a nice, mushy paste which our conscious minds can digest. But whenever one of us notices something that doesn’t exist, or fails to notice something that does exist, our personal version of the world is nudged a little bit further from reality. It makes one wonder how much of reality we all have in common, and how much is all in our minds.”

Which raises a more interesting question about consciousness and bias and the story we tell ourselves about who we are.

bonnet_vision_04

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