Altered brain activity in schizophrenia may cause exaggerated focus on self

January 20, 2009 by Cathryn M. Delude
Altered brain connectivity of default brain network in persons with schizophrenia and first-degree relatives. Colored areas represent an interconnected network of brain regions that show synchronized activity (overlapping black and blue traces) when subjects rest and allow their minds to wander. The amount of synchrony, which reflects the strength of functional connections between the different areas, is increased in patients with schizophrenia. First-degree relatives of persons with the illness also show some increase, although less than patients; this may reflect genetic effects on the brain that increase the risk of developing the disease. Black circle: medial prefrontal cortex. Blue circle: posterior cingulate/precuneus. Graphic courtesy: Susan Whitfield-Gabrieli

(PhysOrg.com) -- Schizophrenia may blur the boundary between internal and external realities by over-activating a brain system that is involved in self-reflection, and thus causing an exaggerated focus on self, a new MIT and Harvard brain imaging study has found.

The traditional view of schizophrenia is that the disturbed thoughts, perceptions and emotions that characterize the disease are caused by disconnections among the brain regions that control these different functions.

But this study, appearing Jan. 19 in the advance online issue of the Proceedings of the National Academy of Sciences, 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 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 1 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 thus 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 behavioral and clinical testing were performed by Larry J. Seidman and colleagues at Harvard Medical School, and the imaging data were analyzed by first author Susan Whitfield-Gabrieli, a research scientist at the MIT Martinos Imaging Center 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. 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.

"We think this may reflect an inability of people with schizophrenia to direct mental resources away from internal thoughts and feelings and toward the external world in order to perform difficult tasks," Whitfield-Gabrieli explained.

The hyperactive default system could also help to explain hallucinations and paranoia by making neutral external stimuli seem inappropriately self-relevant. 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 is also overactive, though to a lesser extent, in first-degree relatives of schizophrenia patients who did not themselves have the disease. This suggests that overactivation of the default system may be linked to the genetic cause of the disease rather than its consequences.

The default system is a hot topic in brain imaging, according to John Gabrieli, partly because it is easy to measure and because it is affected in different ways by different disorders.

Provided by MIT

Explore further: Faulty serotonin 1A receptor 'prevents' calm mental states

Related Stories

Faulty serotonin 1A receptor 'prevents' calm mental states

March 1, 2012
Researchers at the MedUni Vienna have, for the first time, investigated the influence of the serotonin system on the default mode network (DMN) in the human brain and discovered that, in people with depression, the inhibitory ...

The key to effectively treating mental illness—eliminate the stigma

August 10, 2016
In the 1940s, it was cancer. In the '80s, it was HIV. Today, the condition that's battling pervasive social stigma is mental illness.

Researchers using MRI to quantify human intelligence

July 18, 2016
Human intelligence is being defined and measured for the first time ever by researchers at the University of Warwick.

Recommended for you

Want to win at sports? Take a cue from these mighty mice

July 20, 2017
As student athletes hit training fields this summer to gain the competitive edge, a new study shows how the experiences of a tiny mouse can put them on the path to winning.

'Smart' robot technology could give stroke rehab a boost

July 19, 2017
Scientists say they have developed a "smart" robotic harness that might make it easier for people to learn to walk again after a stroke or spinal cord injury.

Engineered liver tissue expands after transplant

July 19, 2017
Many diseases, including cirrhosis and hepatitis, can lead to liver failure. More than 17,000 Americans suffering from these diseases are now waiting for liver transplants, but significantly fewer livers are available.

Lunatic Fringe gene plays key role in the renewable brain

July 19, 2017
The discovery that the brain can generate new cells - about 700 new neurons each day - has triggered investigations to uncover how this process is regulated. Researchers at Baylor College of Medicine and Jan and Dan Duncan ...

New animal models for hepatitis C could pave the way for a vaccine

July 19, 2017
They say that an ounce of prevention is worth a pound of cure. In the case of hepatitis C—a disease that affects nearly 71 million people worldwide, causing cirrhosis and liver cancer if left untreated—it might be worth ...

Omega-3 fatty acids fight inflammation via cannabinoids

July 18, 2017
Chemical compounds called cannabinoids are found in marijuana and also are produced naturally in the body from omega-3 fatty acids. A well-known cannabinoid in marijuana, tetrahydrocannabinol, is responsible for some of its ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.