Studying patients with certain delusions and brain disorders, NYU Langone Medical Center researchers have revealed a consistent pattern of injury to the frontal lobe and right hemisphere of the brain.
Research leader Dr. Orrin Devinsky says that his team's study provides a novel theory for how delusions arise and why they persist.
Writing about the findings in the journal of Neurology, he says that the cognitive deficits caused by these injuries to the right hemisphere lead to the over compensation by the left hemisphere of the brain for the injury, resulting in 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 Dr. Devinsky, professor of Neurology, Psychiatry and Neurosurgery and Director of the NYU Epilepsy Center at NYU Langone Medical Center.
"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," he added.
Delusions are generally described as bizarre pathologic beliefs that remain fixed despite clear evidence that they are incorrect.
"Delusions are common problems in a variety of psychiatric and neurological disorders. Psychiatric disorders with delusions, for example- schizophrenia, have been proven to have functional and structural brain pathology. But now improved diagnostic techniques are allowing us to have increased identification of neurologic disorders among other patient populations with delusions," said Dr. Devinsky.
During the study, the research team observed that the most neurologic patients with delusions usually had lesions in the right hemisphere and/or bifrontal areas.
According to Dr. Devinsky, the right hemisphere of the brain dominates self recognition, emotional familiarity and ego boundaries.
The researcher said that when the right hemisphere of the brain gets injured, the left hemisphere tends to have a creative narrator leading to excessive, false explanations.
He further said that the resistance of delusions to change despite clear evidence that they are wrong likely reflects frontal dysfunction of the brain, which impairs the ability to monitor self and to recognize and correct inaccurate memories and familiarity assessments.
Based on their observations, the study's authors concluded that right hemisphere lesions might cause delusions by disrupting the relation between and the monitoring of psychic, emotional and physical self to people, places, and even body parts.
This, according to them, explains why content specific delusions involve people places or things of personal significance and distort ones relation to oneself.
"Our knowledge of delusions is limited by our ability to comprehend the patients irrational thought process. The pathogenesis of delusions likely includes many mechanisms that span overlapping psychological, cognitive and neurological disorders.
Future research should explore the psychological, cognitive, and pyschologic-anatomic systems that change during the emergence and resolution of delusions as well as strategies to treat delusions," said Dr. Devinsky.