Reading Our Minds by Daniel Barron

Author:Daniel Barron [Daniel Barron]
Language: eng
Format: epub
Published: 0101-01-01T00:00:00+00:00

Schizophrenia

Schizophrenia is a severely disabling illness that warps the fabric of someone’s reality, often tearing it apart. Schizophrenia is sometimes characterized by visual and auditory hallucinations as well as sometimes by quite elaborate ideas or beliefs that a patient will doggedly adhere to even in the absence of evidence.

If we view the brain as an inference machine, we might say that in schizophrenia, the brain struggles to balance what it senses with what it expects to sense, so much so that its expectations override what is actually seen, heard, and felt. Using our forest analogy, in schizophrenia, the brain so strongly expects to see a tree that, even in the absence of a stack of brown pixels, it perceives a tree. This is the quintessential false positive that psychiatrists call a hallucination.

A study recently published in Science described a type of stress test that might help us measure these doggedly stubborn models that—if we view the brain as an inference machine—underlie hallucinations. The project was led by Yale psychiatrist Dr. Al Powers in collaboration with Drs. Phil Corlett and Chris Mathys. The goal of the stress test was to try to train someone to hallucinate and then to measure what happened when they did.

In their stress test, they repeatedly showed people a checkerboard paired with a tone. Every time someone heard a tone, they’d press a button; so checkerboard, tone, button; checkerboard, tone, button. After training people on this “checkerboard then tone” model, Powers stopped playing the tone after the checkerboard. They wanted to see how different individuals would respond: checkerboard, tone, button; checkerboard, [silence], button?

As expected, healthy participants made a few mistakes; even a healthy mind is imperfect. But Powers discovered that people who, even before the stress test, experienced auditory hallucinations (as part of a psychosis or as self-described “clairaudient psychics”) were five times more likely to “hear” nonexistent tones than healthy participants. They were also more certain they heard nonexistent tones.

Powers had found a way to flex the brain so he could measure how someone interacts with the environment. The test further allowed him to find where in the brain a problem might be: As a participant’s certainty that they heard a nonexistent tone increased, so, too, did the activity in brain regions associated with auditory perception. By devising a stress test to create a percept in the absence of sensation, Powers had found a brain region responsible for auditory hallucinations. Since publishing their work, Powers and colleagues have developed an online version of their stress test and are testing whether it proves helpful in treating patients with schizophrenia.

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