- Psychosis, Delusions, and Personality Disorders http://samvak.tripod.com/personalitydisorders69.html Persecutory Anxiety http://samvak.tripod.com/case03.htmlMessage 1 of 1 , Apr 1, 2009View Source=============================
Schizophrenia reassessed as fixation on self
Jan. 23, 2009
Institute of Technology
and World Science staff
Schizophrenia may blur the boundary between internal and external realities by overactivating a brain system involved in self-reflection, causing an exaggerated focus on self, a study has found.
The traditional view of schizophrenia is that the disturbed thoughts, perceptions and emotions characterizing the mental illness result from disconnections among the brain regions that control these different functions.
But the new study found that schizophrenia also involves excess connectivity between brain regions involved in self-reflection which become active when we think of nothing in particular, or of ourselves.
“People normally suppress this ‘default’ system when they perform challenging tasks. But we found that patients with schizophrenia don’t,” said John D. Gabrieli of the Massachusetts Institute of Technology, one of 13 authors of the study, published Jan. 19 in the advance online issue of the research journal Proceedings of the National Academy of Sciences.
The findings “may reflect an inability of people with schizophrenia to direct mental resources away from internal thoughts and feelings and toward the external world,” said MIT’s Susan Whitfield-Gabrieli, also a co-author.
John Gabrieli added that he hopes the research might lead to ways of predicting or monitoring individual patients’ response to treatments for the illness, which occurs in about one percent of people.
Schizophrenia is largely genetic. First-degree relatives of patients (their parents, brothers, sisters, or children) are 10 times more likely to develop the disease than the general population. Which genes are responsible are largely unknown.
The researchers studied three matched groups of 13 subjects each: schizophrenia patients, nonpsychotic first-degree relatives of patients and healthy nonrelatives. They chose recently diagnosed patients, so that differences in prior treatment or psychotic episodes wouldn’t bias the results.
The participants were brain-scanned using a widely used technique known as functional magnetic resonance imaging, while resting and while performing easy or hard memory tasks.
The researchers focused on the “default” system, a network of brain regions whose activity drops when people perform hard mental tasks. This network includes areas of the outer brain known as the medial prefrontal cortex and the posterior cingulate cortex, associated with self-reflection and memories about the self. The network appears to become linked together and active when the mind wanders.
The scientists 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. In other words, the patients were less able than healthy subjects to suppress the network’s activity during the task. Interestingly, the less the suppression and the greater the connectivity, the worse they performed on the hard memory task, and the worse their symptoms.
The hyperactive default system could also help to explain hallucinations and paranoia by making neutral external stimuli seem inappropriately self-relevant, the investigators said. For instance, if brain regions whose activity normally signifies self-focus are active while listening to a voice on television, the person may perceive that the voice is speaking directly to them.
The default system was also overactive, though less so, in first-degree relatives of schizophrenia patients who didn’t themselves have the disease, the researchers said. This suggests overactivation of the default system may be linked to the genetic cause of the disease rather than to its consequences, they added. The default system is a hot topic in brain imaging, said John Gabrieli, partly because it’s easy to measure and is affected in different ways by different disorders.