5 hours ago
The mystery of why there hasn't been a confirmed case of schizophrenia in people born blind
https://www.discovermagazine.com/the-mys...lind-49361
VIDEO EXCERPTS: In 1950, researchers Hector Chevigny and Sydell Braverman set out to, as they put it, “demolish old fables about the emotional life of the blind” and demonstrate that the mental health issues of the blind are no different from those experienced by the sighted.
But they did discover one big — and very surprising — difference: There have been no reported cases of schizophrenia in people blind from birth (or who became blind very shortly after birth). At the time, there was limited patient data available, so it wasn’t clear if this astonishing finding would hold up. But in the almost 80 years since, more national databases of mental illness have been maintained, and still no cases have been found, according to a study in Frontiers in Psychology.
Is it just a coincidence? Or does never having been able to see somehow offer protection from schizophrenia? And if it does, how would that even work?
[...] We tend to think of our brains as something like extremely sophisticated video recorders. But over the past few decades, neuroscience has shown that’s not quite how our brains work. What really happens is that the brain predicts what it expects reality to be, based on what it knows from prior experience.
Then, in a series of iterations, it tweaks that prediction as sensory data becomes available. Sussex University neuroscientist Anil Seth calls this process “controlled hallucinations.” For people with schizophrenia, however, the hallucinations are not always controlled.
What goes awry with the perceptions of people with schizophrenia? One theory, developed by Corlett and others, is that the illness results from prediction errors. People with schizophrenia are likely to give too much weight to sensory input that the rest of us might discount or even ignore.
n one experiment, Corlett and colleagues conditioned study participants to hallucinate, something that he points out is not difficult to do, according to a study from Cambridge University Press. The experiment was simple enough. A visual stimulus, such as a flashing light, was paired with a tone. After several rounds, people began to perceive the tone when they saw the flash of light, even if the tone wasn’t present.
However, people who were already prone to hearing voices in their heads were 10 times more likely than other participants to hallucinate a tone in the lab. The fact that people who hear voices in their heads report hearing the tone much more frequently suggests that they have a bias toward expecting auditory stimulation, Corlett explained.
[...] So what does this have to do with blindness? The visual system is the area of the brain most extensively connected with other parts of the brain. It’s important not just for seeing but also for attention, learning, and even processing emotions. This prominence of the visual system is why it plays an important role even in auditory hallucinations.
The visual system is extremely important when it comes to psychosis tendencies because it’s important for creating expectations, Corlett said.. [...] “If you don't have the visual system, which is a dominant way of making predictions, then maybe you don't have this over-expectation of auditory stimuli, or maybe your expectations about auditory stimuli are different,” Corlett told Discover. “And that might protect you against this subsequent development of psychotic symptoms.” (MORE - missing details)
https://www.discovermagazine.com/the-mys...lind-49361
VIDEO EXCERPTS: In 1950, researchers Hector Chevigny and Sydell Braverman set out to, as they put it, “demolish old fables about the emotional life of the blind” and demonstrate that the mental health issues of the blind are no different from those experienced by the sighted.
But they did discover one big — and very surprising — difference: There have been no reported cases of schizophrenia in people blind from birth (or who became blind very shortly after birth). At the time, there was limited patient data available, so it wasn’t clear if this astonishing finding would hold up. But in the almost 80 years since, more national databases of mental illness have been maintained, and still no cases have been found, according to a study in Frontiers in Psychology.
Is it just a coincidence? Or does never having been able to see somehow offer protection from schizophrenia? And if it does, how would that even work?
[...] We tend to think of our brains as something like extremely sophisticated video recorders. But over the past few decades, neuroscience has shown that’s not quite how our brains work. What really happens is that the brain predicts what it expects reality to be, based on what it knows from prior experience.
Then, in a series of iterations, it tweaks that prediction as sensory data becomes available. Sussex University neuroscientist Anil Seth calls this process “controlled hallucinations.” For people with schizophrenia, however, the hallucinations are not always controlled.
What goes awry with the perceptions of people with schizophrenia? One theory, developed by Corlett and others, is that the illness results from prediction errors. People with schizophrenia are likely to give too much weight to sensory input that the rest of us might discount or even ignore.
n one experiment, Corlett and colleagues conditioned study participants to hallucinate, something that he points out is not difficult to do, according to a study from Cambridge University Press. The experiment was simple enough. A visual stimulus, such as a flashing light, was paired with a tone. After several rounds, people began to perceive the tone when they saw the flash of light, even if the tone wasn’t present.
However, people who were already prone to hearing voices in their heads were 10 times more likely than other participants to hallucinate a tone in the lab. The fact that people who hear voices in their heads report hearing the tone much more frequently suggests that they have a bias toward expecting auditory stimulation, Corlett explained.
[...] So what does this have to do with blindness? The visual system is the area of the brain most extensively connected with other parts of the brain. It’s important not just for seeing but also for attention, learning, and even processing emotions. This prominence of the visual system is why it plays an important role even in auditory hallucinations.
The visual system is extremely important when it comes to psychosis tendencies because it’s important for creating expectations, Corlett said.. [...] “If you don't have the visual system, which is a dominant way of making predictions, then maybe you don't have this over-expectation of auditory stimuli, or maybe your expectations about auditory stimuli are different,” Corlett told Discover. “And that might protect you against this subsequent development of psychotic symptoms.” (MORE - missing details)