People who hear voices — both with and without a diagnosed psychotic illness — are more sensitive than other subjects to a 125-year-old experiment designed to induce hallucinations. And the subjects’ ability to learn that these hallucinations were not real may help pinpoint those in need of psychiatric treatment, suggests a new Yale-led study published Aug. 11 in the journal Science. The research has been carried out by Philip Corlett and Al Powers, Yale University, and Chris Mathys, SISSA.
People with schizophrenia and other psychotic illnesses often report hearing voices, but so do other people with no diagnosed psychiatric disorder.The researchers wanted to identify factors that contribute to auditory hallucinations and to tease apart what makes some people’s experiences troubling and others’ benign.
Using a Pavlovian learning task, the scientists induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, they identified processes that differentiated voice-hearers from non–voice-hearers and treatment-seekers from non–treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations.
"These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without" wrote the researchers in the article.
The Brain & Behavior Research Foundation was primary funder of the research.