fMRI Scans Reveal Brain’s Processing of Low-Priority Ideas

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When individuals place an idea on the back burner, it goes into a processing area of the brain called the default-mode network. This network enables the brain to hold the low-priority idea in abeyance until a time when they are not busy with something else.

“The default-mode network appears to be the brain’s back burner for social decision making,” said Peter T. Fox, M.D., director of the Research Imaging Institute at The University of Texas Health Science Center at San Antonio (USA). “Usually these back-burner ideas relate to interpersonal interactions and decisions that can't readily be quantified and shouldn't be rushed.”

Dr. Fox compared this to putting a computer batch job into background processing to wait until the system is less busy. A recently released study from the Research Imaging Institute and other institutions offers evidence that genetics plays a role in this back-burner setup, which has been shown to be abnormal in a variety of psychiatric disorders.

The study was published in the January 18-22, 2010, online edition of the journal Proceedings of the [U.S.] National Academy of Sciences (PNAS). The default-mode network is one of several neural networks that operate whether the mind is at rest or is occupied doing a task. A separate PNAS study, published in 2009 by Dr. Fox and the same collaborators, presented a strong case that all human behaviors may be accurately viewed as cooperative interactions among these networks, according to Dr. Fox.

The newer research estimated the importance of genetic effects on the default-mode network by creating maps of eight anatomically distinct regions within the network. These maps were obtained by functional magnetic resonance imaging (fMRI) studies in 333 individuals from 29 randomly selected, extended-family pedigrees.

Network connectivity and gray-matter density were correlated to genetic factors. “We found that more than 40% of the between-subject variance in functional connectivity within the default-mode network was under genetic control,” Dr. Fox said. Based on this information, it is possible new diagnostic tools could be considered for various psychiatric or neurological illnesses, he noted.

The study also included collaborators from the Yale University School of Medicine (New Haven, CT, USA), the University of Oxford (Oxford, UK), and Imperial College (London, UK). “One long-term research goal is to test whether other intrinsically connected networks are also under genetic control, which we expect they will be,” Dr. Fox concluded. “We also want to identify the genes that are controlling the default-mode network and other networks, and identify disorders associated with their abnormalities. A final goal is to develop treatment strategies.”