According to a survey published in the World Mental Health Study, about 1 in 20 people have experienced hallucinations at least once in their lives. While hallucination has been known as a symptom for psychosis, some neurologists believe that even normal people have tendencies to see or hear things that aren't actually there.
Yahoo Health reports a new study published in the journal PNAS suggests that hallucinations are brought about by normal brain functioning. "It's not a broken brain that generates hallucinations," said Christoph Teufel, a neuroscientist at University in Cardiff in Wales, "it's just part of how the brain works."
Teufel, who specializes in the neuroscience of vision, and his colleagues including University of Cambridge psychiatrist Paul Fletcher concluded that hallucinations are the brain's way to fill the gap in our visual system. Although it has been understood that the eyes record images to be processed by the brain, Teufel hypothesized that our visual system aren't actually that detailed --- prompting the brain to recall previous information to fill in.
To test this theory, the researchers conducted experiments using black-and-white images that "looked like meaningless black and white blobs," involving 16 healthy adults and 18 adults who had experienced few signs of psychosis but were not diagnosed with the mental disorder.
The participants were asked to identify the person or object found in the confusing images and were then shown coloured photographs where the black-and-white images were based. Shortly after, the participants were asked to identify the person and object in those black and white images all over again.
Results show that those who experienced symptoms of psychosis did better in the second test compared to normal adults. This indicates that their brains were better in using prior information to fill the gaps in their visual system.
While results of the study have proven that hallucinations happen to normal people, Teufel said "there's a continuum between mental illness and mental health," and they are planning to conduct further studies to learn more of that.
