It had been more than a decade since “B.T.” had last seen anything. After suffering a traumatic accident as a young woman, doctors diagnosed her with cortical blindness, caused by damage to the visual processing centers in her brain. So she got a seeing eye dog to guide her and grew accustomed to the darkness.
Besides, B.T. had other health problems to cope with — more than 10 wildly different personalities that competed for control of her body. It was while seeking treatment for her dissociative identity disorder that the ability to see suddenly returned. Not to B.T., a 37-year-old German woman. But to a teenage boy she sometimes became.
With therapy, over the course of months, all but two of B.T.’s identities regained their sight. And as B.T. oscillated between identities, her vision flicked on and off like a light switch in her mind. The world would appear, then go dark.
Writing in PsyCh Journal, B.T.’s doctors say that her blindness wasn’t caused by brain damage, her original diagnosis. It was instead something more akin to a brain directive, a psychological problem rather than a physiological one.
B.T.’s strange case reveals a lot about the mind’s extraordinary power — how it can control what we see and who we are.
B.T. exhibited more than 10 personalities, each of them varying in age, gender, habits and temperament. They even spoke different languages: Some communicated only in English, others only in German, some in both (B.T. had spent time in an English-speaking country as a child but lived in Germany).
One explanation, that B.T. was “malingering”, or lying about her disability, was disproved by an EEG test.
When B.T. was in her two blind states, her brain showed none of the electrical responses to visual stimuli that sighted people would display — even though B.T.’s eyes were open and she was looking right at them.
Doctors believe that B.T.’s blindness is psychogenic (psychologically caused, rather than physical). Something happened — perhaps related to her accident — that caused her body to react by cutting out her ability to see. Even now, two of her identities retain that coping mechanism.
It’s not actually all that uncommon for people’s brains to stop them from seeing, even when their eyes work fine, the researchers say. When your two eyes see slightly different images — when squinting, for example — the brain will cut out one image to keep you from getting confused by the contradiction. Your brain also intervenes in visual processing when you focus on particular objects in your field of vision.
Source: www.washingtonpost.com
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