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How the brain generates delusions

January 15, 2009 |  1:44 pm

Brain1People with certain types of brain disorders can suffer from delusions, which are erroneous beliefs in objects or situations that remain fixed in the mind despite evidence they are incorrect. Delusions make it hard for people to function with any normalcy in the real world and confound the doctors and therapists who are trying to help them.

Research published this week in the journal Neurology makes an important observation about the brains of people with neurological disorders, such as those with brain damage from strokes and Alzheimer's disease who suffer delusions, and suggests a novel theory for why delusions occur and persist. Researchers at New York University Langone Medical Center studied neurological patients with delusions and found a consistent pattern of injury to the front lobe and right hemisphere of the brain. It's possible that injury on the right side leads to overcompensation by the left hemisphere, thus producing delusions.

"Problems caused by these brain injuries include impairment in monitoring of self, awareness of errors and incorrectly identifying what is familiar and what is a work of fiction," said the lead author of the study, Dr. Orrin Devinsky, in a news release. "However, delusions result from the loss of these functions as well as the over activation of the left hemisphere and its language structures that 'create a story,' a story which cannot be edited and modified to account for reality. Delusions result from right hemisphere lesions, but it is the left hemisphere that is deluded."

The fact that people believe delusions despite evidence that they are wrong may be due to the dysfunction in the frontal lobe of the brain.

The research could be helpful by clarifying what psychological, cognitive and neurological mechanisms contribute to delusional thinking, the researchers said. That may lead to better strategies to treat the illness.

-- Shari Roan