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Medical News Today: Are brain structure differences to blame for hallucinations?

Some people with schizophrenia have hallucinations, which means they see, hear, smell or feel things that nobody else experiences. Now, a new study sheds light on this condition and suggests that there are differences in a key region of the brain for people with schizophrenia who have hallucinations, compared with those who do not.
Hallucinating man
People with schizophrenia can have hallucinations in which they see, hear, smell or feel things that are not there. New research suggests this may be down to a structural difference in the brain.

The researchers – led by Dr. Jon Simons from the University of Cambridge in the UK – publish their study in the journal Nature Communications.

According to the National Institute of Mental Health (NIMH), scientists have long known that schizophrenia runs in families; it occurs in 1% of the general population but in 10% of people with a first-degree relative with the disorder.

For quite some time, researchers have believed that an imbalance in the chemical reactions of the brain could play a role in schizophrenia.

But in a previous study, Dr. Simons and colleagues found that variations in the length of a fold toward the front of the brain – known as the paracingulate sulcus (PCS) – in healthy individuals was associated with the ability to distinguish real from imagined information, which is a process known as “reality monitoring.”

“Schizophrenia is a complex spectrum of conditions that is associated with many differences throughout the brain,” explains Dr. Simons, “so it can be difficult to make specific links between brain areas and the symptoms that are often observed.”

The researchers note that the PCS is one of the last structural folds in the brain to develop before birth, and it varies in size among individuals.

For their new study, the team measured the length of the PCS in 153 structural MRI scans of people diagnosed with schizophrenia and matched them with those of control participants.

Shorter PCS fold increases hallucination risk by 20%

Dr. Simons and colleagues wanted to determine whether there was a link between PCS length and being predisposed to hallucinations.

Fast facts about schizophrenia

  • About 1% of Americans have schizophrenia
  • Symptoms such as hallucinations and delusions typically start between 16-30 years of age
  • Males tend to experience symptoms earlier than females.

Learn more about schizophrenia

After studying the MRI scans, the researchers found that a 1-cm reduction in the PCS fold’s length increased the likelihood of hallucinations by nearly 20% in those who were diagnosed with schizophrenia.

Furthermore, this effect was observed across all types of hallucinations, whether they were auditory or visual, which the team says is consistent with a reality monitoring issue.

The researchers say brain areas that process visual and auditory information may produce modified perceptions that appear real for people who experience hallucinations; these altered perceptions may be due to differences in reality monitoring processes that are supported by regions near the PCS.

A person may imagine a voice, for example, but perceive that it comes from the outside world.

First author of the study Dr. Jane Garrison says:

“We think that the PCS is involved in brain networks that help us recognize information that has been generated ourselves. 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.”

She adds that hallucinations are complex and there “is likely to be more than one explanation for why they arise, but this finding seems to help explain why some people experience things that are not actually real.”

In August of this year, Medical News Today reported on a study that found a link between throat microbes and schizophrenia.

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