Scientists define brain network behind attention, daydreaming

by Geoffrey Mohan

Stanford neuroscientists have for the first time traced how three brain networks mediate the mind's internal focus and its processing of stimuli from the outside world.

By stimulating neurons with electromagnets, the researchers demonstrated how the brain's executive and salience networks - crucial for cognition and decision-making - inhibit the default mode network, which centers on self-directed processes such as introspection, recall and rumination.

"As you engage in any task that's attention demanding, you activate these outside world networks - the executive and salience network - and you deactivate or turn down the default mode network," said Stanford neuroscientist and psychiatrist Dr. Amit Etkin, lead author of the study published online Monday in Proceedings of the National Academy of Sciences.

Dysfunction among those networks has been implicated in a broad array of , including depression, , autism and schizophrenia.

Imaging studies had long ago established strong correlations among these networks, but the causal path of their interplay had been indecipherable from the data produced through functional magnetic resonance imaging, or fMRI, according to the authors.

"You don't actually know which events were responsible for which other events," said Etkin, who also works with the Veterans Administration Palo Alto Health Care System. "That is, you don't really have a sense of causality."

The researchers used trans-cranial , a technique that applies a magnetic field to alter the electrochemical signaling in neurons. It has been used for decades to test brain function, and has been approved for treatment of depression.

When applied to discreet areas in the cortex, the magnetic fields provoked responses, evident on fMRI scans, that resembled voluntary brain activity. Researchers then measured the effect of stimulating the executive and salience networks, and recorded a drop in activity in the . When they used a low-frequency magnetic field to inhibit the executive and salience network, the default mode showed heightened activity.

The study also turned up intriguing clues toward new therapies. One of the executive network nodes they stimulated was closely associated with inhibiting a specific area of the default mode that scientists believe is crucial to the antidepressant effects of magnetic stimulation and drug therapies. That could offer neurological clues to why magnetic stimulation appears to work - an effect that has remained somewhat mysterious.

"We're already starting to think about how to use this for novel treatments," Etkin said. "If the default mode were abnormal in patients - which we know to be true for a range of psychiatric disorders - and you knew how to modulate it in the right way, which is what this study provides, then you would have a very important insight into how to potentially remediate these circuits for treatment of these disorders."

add to favorites email to friend print save as pdf

Related Stories

Imaging the magnetically stimulated brain

Nov 19, 2013

(Medical Xpress)—MRI scanners have steadily increased in power, giving researchers ever finer-grained snapshots of the brain in action. However just as modern day fighters can pull high G turns that would ...

Researchers show brain's battle for attention

Apr 11, 2013

(Medical Xpress)—We've all been there: You're at work deeply immersed in a project when suddenly you start thinking about your weekend plans. It happens because behind the scenes, parts of your brain are ...

Brain network decay detected in early Alzheimer's

Aug 19, 2013

In patients with early Alzheimer's disease, disruptions in brain networks emerge about the same time as chemical markers of the disease appear in the spinal fluid, researchers at Washington University School of Medicine in ...

Recommended for you

New ALS associated gene identified using innovative strategy

17 hours ago

Using an innovative exome sequencing strategy, a team of international scientists led by John Landers, PhD, at the University of Massachusetts Medical School has shown that TUBA4A, the gene encoding the Tubulin Alpha 4A protein, ...

Can bariatric surgery lead to severe headache?

17 hours ago

Bariatric surgery may be a risk factor for a condition that causes severe headaches, according to a study published in the October 22, 2014, online issue of Neurology, the medical journal of the American Academy of Neurol ...

Bipolar disorder discovery at the nano level

17 hours ago

A nano-sized discovery by Northwestern Medicine scientists helps explain how bipolar disorder affects the brain and could one day lead to new drug therapies to treat the mental illness.

Brain simulation raises questions

21 hours ago

What does it mean to simulate the human brain? Why is it important to do so? And is it even possible to simulate the brain separately from the body it exists in? These questions are discussed in a new paper ...

User comments