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St. Louis, MO, USA. A brain network linked to introspective tasks — forming the self-image or understanding the motivations of others — is less intricate and well-connected in children, scientists have learned. They also showed that the network establishes firmer connections between various brain regions as an individual matures. Children have more direct access to their self-identification and introspection, with external capabilities developing as they mature into adults.
In papers published in recent years, researchers at Washington University in St. Louis have identified two networks that they think control much of the brain activity behind behaviors directed toward "external" goals, including observing and interacting with the environment.
The maturing architecture of the brain's default network. Damien A. Fair, Alexander L. Cohen, Nico U. F. Dosenbach, Jessica A. Church, Francis M. Miezin, Deanna M. Barch, Marcus E. Raichle, Steven E. Petersen, and Bradley L. Schlaggar. PNAS, vol. 105, no. 10, 4028–4032. doi: 10.1073 / pnas.0800376105.
The scientists, at the WU School of Medicine, are working to establish a picture of how these connections and other brain networks normally develop and interact. They want to use that picture to conduct more detailed assessments of the effects of aging, brain injuries and conditions such as autism on brain function.
Neuroscientists including co-author Marcus E. Raichle, M.D., professor of radiology, of anatomy and neurobiology and of neurology first identified the network, which is called the default network, in 1996.
Since then, scientists have linked it to a number of inward-looking activities, including the creation of the "autobiographical self," a person's internal narrative of their life story; and "mentalizing," the ability to analyze the mental states of others and use those insights to adjust the self's behavior appropriately.
Senior author Bradley L. Schlaggar, M.D., Ph.D, says "Having this information will not only help us understand what's going wrong in these patients, it will also allow us to better assess whether and how future interventions are providing those patients with effective treatment."
Bradley Schlaggar is an associate professor of pediatrics, radiology, neurology and anatomy and neurobiology. Working with Raichle and colleagues that include Steve Petersen, Ph.D., the research team has been using a new technique called resting-state functional connectivity MRI to identify brain networks and analyze their functions and development.
Instead of analyzing mental activity when a volunteer works on a cognitive task, resting-state connectivity scans their brains after they have been asked to rest and not engage in any specific tasks. Steve Petersen is the James McDonnell Professor of Cognitive Neuroscience and professor of neurology and psychology.
The scans reveal changes in the oxygen levels in blood flowing to different areas of the brain. Researchers interpret correlations in the rise and fall of blood oxygen to differetogether. In neuroscientist's terms, this means the regions have functional connectivity.
Damien A. Fair, a graduate student in Schlaggar's lab, led the study, comparing functional connectivity in 13 brain regions linked to the default network in children ages seven to nine and adults ages 21 to 31. "The difference between children and adults is profound," Fair says.
"In a graph depicting the strength of connections between the brain regions we studied, children's minds have just a few connections between some regions, while the adult brains have a web-like mesh of many different interconnecting links involving all the regions."
Schlaggar and colleagues plan further study of how the brain networks interact during development and in the mature brain. They also are looking at how network functions differ in patients with brain injuries and conditions such as autism.
"Autism spectrum disorder first manifests earlier than the time period we were studying," Schlaggar notes. "But many of the functions it affects have been associated with the default network, so we're eager to see if analysis of this network and its development can give us new insights into autism."
The maturing architecture of the brain's default network. Damien A. Fair, Alexander L. Cohen, Nico U. F. Dosenbach, Jessica A. Church, Francis M. Miezin, Deanna M. Barch, Marcus E. Raichle, Steven E. Petersen, and Bradley L. Schlaggar. PNAS, vol. 105, no. 10, 4028–4032. doi: 10.1073 / pnas.0800376105.
Abstract. In recent years, the brain's "default network," a set of regions characterized by decreased neural activity during goal-oriented tasks, has generated a significant amount of interest, as well as controversy. Much of the discussion has focused on the relationship of these regions to a "default mode" of brain function. In early studies, investigators suggested that, the brain's default mode supports "self-referential" or "introspective" mental activity. Subsequently, regions of the default network have been more specifically related to the "internal narrative," the "autobiographical self," "stimulus independent thought," "mentalizing," and most recently "self-projection." However, the extant literature on the function of the default network is limited to adults, i.e., after the system has reached maturity. We hypothesized that further insight into the network's functioning could be achieved by characterizing its development. In the current study, we used resting-state functional connectivity MRI (rs-fcMRI) to characterize the development of the brain's default network. We found that the default regions are only sparsely functionally connected at early school age (7–9 years old); over development, these regions integrate into a cohesive, interconnected network.
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Richard Smith, Editor-in-Chief, introduces Cases Journal. Dr. Smith urges all physicians to submit their case reports to the new open access Cases Journal, which publishes case reports from any area of healthcare.
Cases Journal will publish any case report that is understandable, ethical, authentic, and includes all essential information. A more selective companion, the Journal of Medical Case Reports, publishes original and interesting case reports that contribute significantly to medical knowledge. Article submissions are subject to potential publication by either journal. All reports will be entered in a common and open access database.
Neuroscientists including co-author Marcus E. Raichle, M.D., professor of radiology, of anatomy and neurobiology and of neurology first identified the network, which is called the default network, in 1996. 
Senior author Bradley L. Schlaggar, M.D., Ph.D, says "Having this information will not only help us understand what's going wrong in these patients, it will also allow us to better assess whether and how future interventions are providing those patients with effective treatment." 
Damien A. Fair, a graduate student in Schlaggar's lab, led the study, comparing functional connectivity in 13 brain regions linked to the default network in children ages seven to nine and adults ages 21 to 31. "The difference between children and adults is profound," Fair says. 
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