The neural systems that control self-reflection may be over active in schizophrenic patients, causing these individuals to confuse reality and delusion, according to a recent study by Alan Green, chair of the psychiatry department at Dartmouth Medical School, and 12 other researchers.
Schizophrenia is a mental disorder that affects a patient's perception of reality, often causing hallucinations or paranoid delusions.
The study found that schizophrenia patients are less able to suppress activity in the "default system" of the brain, which is the neural network that is activated when a person is engaged in self-reflection or not focusing on a specific task.
"Normally this network of the brain calms down when people focus on things," Green said. "In people with schizophrenia, it doesn't decrease as much."
A hyperactive default system may also cause schizophrenic patients to experience hallucinations and paranoia because they cannot fully suppress their internal thoughts, which may then appear to manifest in reality.
Schizophrenia patients often focus more on their inner thoughts than on the events around them, Green said, adding that the results of the study could help to explain this behavior.
The study's findings may help researchers to refine current treatment methods, Green said.
"It could conceivably help [researchers] to understand how to track the effectiveness of treatment and how to use treatment in the earlier phases of the disorder," he said.
The researchers studied 13 subjects with schizophrenia who had recently been diagnosed with the disease, in an effort to avoid the possibility that differences in previous treatment would skew the results, according to the study.
Researchers obtained MRIs of patients while they were resting or performing memory tasks that involved focusing on letters. Schizophrenia patients displayed significantly greater default system activity than control subjects, and recorded worse results in the difficult memory task, according to the study.
The researchers tested whether the over-activation was a cause, rather than a symptom, of schizophrenia by evaluating immediate relatives of schizophrenia patients who do not themselves have the disorder, Green said. The relatives also displayed a comparatively high activity in the default system, though to a lesser degree than patients with the disease, Green said.
The research team, which primarily focuses on the genetic causes of schizophrenia, chose to study the brain default system both because it is affected by many different disorders and because it is easy to measure activity in the network, according to a DMS press release.
This is the first study to find a link between schizophrenia and the default system, Green said, adding that he expected that other teams would soon attempt to duplicate the results.
The results of the study were published in the Jan. 27 edition of the Proceedings of the National Academy of Sciences.
Behavioral testing for the study was conducted at Harvard Medical School, and imaging data were analyzed at the MIT Martinos Imaging Center at the McGovern Institute for Brain Research.
Of the 13 authors on the study, most are affiliated with Harvard or MIT. Green joined DMS in 2002.
