Default mode network impaired in young adults at risk for psychosis

Young adults at genetic risk for psychosis show reduced activity in the default mode network (DMN) area of the brain compared with those without such a family history, researchers report.

The findings follow previous research showing reduced DMN activity in patients with psychosis, and suggest that DMN dysfunction may be heritable.

Tuomas Jukuri (Institute of Clinical Medicine, Oulu, Finland) and team explain that the DMN is an important resting state network that is localized in the ventromedial prefrontal cortex extending to the ventral anterior cingulate cortex, the posterior cingulate cortex (PCC), and the precuneus and lateral parietal cortex. It activates while resting and deactivates during the performance of demanding cognitive tasks.

The DMN is associated with the processing of episodic memory, attention to internal emotional states, self-referential processing, and task-independent thought. It is also believed to play a role in generating spontaneous thoughts during mind-wandering or daydreaming, and may be an essential component of creativity.

The researchers studied 72 unaffected young adults, aged an average of 22 years, with a history of psychosis in one or both parents and 72 age-matched mentally healthy individuals without a parental history of psychosis (controls) who participated in the Oulu Brain and Mind study.

Participants with parental history of psychosis had lower educational levels than controls, but there were no significant between-group differences regarding mean IQ.

All of the participants underwent resting state functional magnetic resonance imaging and activity in the DMN was assessed.

The researchers found that participants with a parental history of psychosis had significantly lower levels of activity in the PCC (Brodmann's areas 23 and 31) compared with controls. This area is the central node of the DMN, they note in Schizophrenia Research.

There were no areas of the DMN in which the at-risk group showed greater levels of activity than the control group.

The results suggest that "familial risk for psychotic disorders may be mediated through genetic effects on connectivity in the PCC," comment Jukuri et al.

However, they add: "While this study suggests an important finding, several questions remain unanswered, including the mechanism leading to hypoactivity in the PCC and the potential for the DMN to ultimately be useful in early detection of psychosis risk.

"Follow-up studies of the DMN functions may reveal the relevance of the R-fMRI [resting state functional magnetic resonance imaging] method in helping to find those individuals at most risk of developing psychosis."

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