How Do Delusions Form in the Brain?
September 23, 2013. Seeing may be believing, but believing can also sway what we see. That’s the message of a study published August 21 in the Journal of Neuroscience which outlines a way for small abnormalities in perception to give rise to the strange, fixed beliefs of people with schizophrenia. The study, led by Philipp Sterzer of Charité Universitätsmedizin Berlin, Germany, highlights the basic processes through which we perceive the world around us. We manage to experience the world as a stable place, despite receiving noisy inputs to the contrary. That’s because the brain constantly interprets sensory signals based on previous experience: For example, hearing only a single note of our cell phone’s ring tone is enough for us to recognize that our cell phone is indeed ringing.
The study suggests that problems with this process of interpreting could create and maintain these bizarre beliefs, called delusions. First author Katharina Schmack and colleagues studied healthy volunteers who had also been scored on their tendency to hold mild, delusion-like beliefs. They found that those who were more delusion prone also reported seeing more changes in the direction of a rotating sphere on a screen: The sphere alternated between leftward and rightward rotation more quickly for them compared to those with lower delusion scores. Also, sphere rotation could be shaped by a false belief: When the participants wore glasses which they were falsely told would make them see rotation in mainly one direction (they were, in fact, just clear glass), the participants reported a similar shift in their perception, and this shift was more pronounced in those with higher delusion scores.
This study suggests that a self-fulfilling interaction may underlie delusions: Perceptual instabilities drive people to form an odd belief to explain the strange events taking place around them. This belief, in turn, molds perception to fit with it. (For more details, see the related news story.)—Michele Solis.