Schizophrenia causes exaggerated focus on self

January 22nd, 2009 - 3:56 pm ICT by IANS  

Washington, Jan 22 (IANS) Schizophrenia blurs the line between inner and outer reality, by overstimulating a brain region involved in self-reflection and causing exaggerated focus on self. The traditional view of schizophrenia is that the disturbed thoughts, perceptions and emotions that characterise the condition are caused by disconnections among the brain regions that control these different functions.

But a new study found that schizophrenia also involves an excess of connectivity between the so-called default brain regions, which are involved in self-reflection and become active when we are thinking about nothing in particular, or thinking about ourselves.

“People normally suppress this default system when they perform challenging tasks, but we found that patients with schizophrenia don’t do this,” said John D. Gabrieli, a professor in the McGovern Institute for Brain Research at Massachusetts Institute of Technology (MIT) and one of the study’s 13 authors.

“We think this could help to explain the cognitive and psychological symptoms of schizophrenia.”

Gabrieli added that he hopes the research might lead to ways of predicting or monitoring individual patients’ response to treatments for this mental illness, which occurs in about one percent of the population.

Schizophrenia has a strong genetic component, and first-degree relatives of patients (who share half their genes) are 10 times more likely to develop the disease than the general population. The identities of these genes and how they affect the brain are largely unknown.

The researchers studied three carefully matched groups of 13 subjects each: schizophrenia patients, nonpsychotic first-degree relatives of patients and healthy controls. They selected patients who were recently diagnosed, so that differences in prior treatment or psychotic episodes would not bias the results.

The subjects were scanned by functional magnetic resonance imaging (fMRI) while resting and while performing easy or hard memory tasks.

The behavioural and clinical testing were performed by Larry J. Seidman and colleagues at Harvard Medical School, and the imaging data were analysed by first author Susan Whitfield-Gabrieli, a research scientist at the MIT Martinos Imaging Centre at the McGovern Institute.

The researchers were especially interested in the default system, a network of brain regions whose activity is suppressed when people perform demanding mental tasks.

This network includes the medial prefrontal cortex and the posterior cingulate cortex, regions that are associated with self-reflection and autobiographical memories and which become connected into a synchronously active network when the mind is allowed to wander.

Whitfield-Gabrieli found that in the schizophrenia patients, the default system was both hyperactive and hyperconnected during rest, and it remained so as they performed the memory tasks, said a MIT release.

In other words, the patients were less able than healthy control subjects to suppress the activity of this network during the task.

Interestingly, the less the suppression and the greater the connectivity, the worse they performed on the hard memory task, and the more severe their clinical symptoms.

These findings appeared in the January advance online issue of the Proceedings of the National Academy of Sciences.

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