June 19, 2007 -- A probe of the upper echelons of the human brain's chain-of-command has found strong evidence that there are not one but two complementary commanders in charge of the brain, according to neuroscientists at Washington University School of Medicine in St. Louis.
It's as if Captains James T. Kirk and Jean-Luc Picard were both on the bridge and in command of the same starship Enterprise.
In reality, these two captains are networks of brain regions that do not consult each other but still work toward a common purpose — control of voluntary, goal-oriented behavior. This includes a vast range of activities from reading a word to searching for a star to singing a song, but likely does not include involuntary behaviors such as control of the pulse rate or digestion.
Brain scans show two separate networks of nodes making decisions.
Using an analytic technique originally developed by Raichle's group, scientists employed resting state functional connectivity MRI to identify pairs of brain regions where blood oxygen levels rose and fell roughly in synch with each other, implying the regions likely work together. They graphed the results, representing each brain region with a shape. They drew a line between paired brain regions if their blood oxygenation patterns correlated tightly enough. "You might expect that everything is connected to everything, and you would get sort of a big mess and not much information," Dosenbach says. "But that's not at all what we found. Even at low levels of correlation, there were two sides to these graphs. Brain regions on either side had multiple connections to other regions on their side, but they never connected to regions on the opposite side."
The two networks seem to have different purposes. The frontoparietal network sounds like it is more reactive.
Having established that two control networks existed, researchers turned back to their functional brain scans for insight into the networks' roles. One network, dubbed the cinguloopercular network, was linked to a "sustain" signal.
"When you start doing a task, this signal turns on," Petersen explains. "It stays constant while you're doing the task, and then when you're done it turns off."
In contrast, the frontoparietal network was consistently active at the start of mental tasks and during the correction of errors.
The balance between the two networks could vary from individual to individual. For example, some people might be better at maintaining a constant activity and others might be better at reacting to events.
|Share |||Randall Parker, 2007 June 19 10:58 PM Brain Intelligence|