It’s thought that around half of all people experience some form of hallucination, be it auditory, visually, through smell or touch. But for those diagnosed with schizophrenia, the odds are much higher with an estimated three out four sufferers experiencing things that aren’t actually there. It now seems that schizophrenics who are prone to hallucinations have actual structural differences in their brains when compared to those who have the mental health condition but don’t experience hallucinations.
In a new paper published in Nature Communications, researchers compared the brains of sufferers of schizophrenia who experience hallucinations, and those who don’t. In particular, they looked at the structural differences in a key region of the brain involved with the distinction between real and imagined information, a fold called the paracingulate sulcus (PCS). Located at the front of the brain, they found that a reduction in the length of this particular region was linked to an increased chance that the patient will have hallucinations.
“Schizophrenia is a complex spectrum of conditions that is associated with many differences throughout the brain, so it can be difficult to make specific links between brain areas and the symptoms that are often observed,” explains Dr. Jon Simons of the University of Cambridge, who co-authored the paper. “By comparing brain structure in a large number of people diagnosed with schizophrenia, with and without the experience of hallucinations, we have been able to identify a particular brain region that seems to be associated with a key symptom of the disorder.”
The researchers looked at the MRI scans of 153 patients with schizophrenia and matched them to controls, taking into account brain volume, surface area, handedness, sex, and age, among many other criteria. They then measured the lengths of each person’s PCS, and found that a reduction in length of 1 centimeter (0.4 inch) translated to a 19.9 percent increase in the likelihood that they would experience hallucinations, regardless of whether the patient’s experiences were auditory or visual.
Other changes in the brain are also no doubt important in the forming of hallucinations, and are probably related to those parts which process either sight or sound information, depending on which types of hallucinations are experienced. The researchers suggest that as the brain produces this altered auditory or visual information which doesn't actually exist, it could be that when this is then passed into the PCS, which is responsible for the monitoring of reality, that the brain misinterprets the information as being real.
“We think that the PCS is involved in brain networks that help us recognise information that has been generated ourselves,” says Dr. Jane Garrison, another of the co-authors of the study. “People with a shorter PCS seem less able to distinguish the origin of such information, and appear more likely to experience it as having been generated externally.”
The researchers note that there probably are multiple causes behind the experiencing of hallucinations, and that this could just help explain one facet of the phenomena.