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An fMRI scan of the upper echelons of the human brain, reveals that there are apparently two commanders at the helm, according to US neuroscientists; it is as if Russell Crowe were joined by his twin brother to captain the ship. The work may suggest new insights into behavioural problems that occur following brain injury. Neuroscientist Steven Petersen and his team at Washington University School of Medicine in St. Louis also found that these two captains at a single helm do not consult each other in the control of voluntary, goal-oriented behaviour. Such behaviour encompasses a vast range of activities from reading and surfing the net to singing a song or even sailing a ship. In contrast, involuntary behaviour, such as pulse rate, breathing, and digestion are not controlled in this way. "This was a big surprise," says Petersen, "We knew several brain regions contribute to top-down control, but most of us thought we'd eventually show all those regions linking together in one system, one little guy up top telling everyone else what to do." This does not appear to be the case. Philosophical implications aside, the work may aid efforts to understand the effects of brain injury. Peculiar behaviour can arise following brain injury. "One man with a brain injury started undressing every time he saw a bed, regardless of whether it was in a furniture store or his own bedroom," explains team member Nico Dosenbach, "This research may help us understand what's happening to these patients." The work builds on earlier work by Dosenbach, Petersen and others, in which they identified brain regions that were consistently active as volunteers prepared for a mental task. They suggested that the regions were creating task sets, plans for using the specialized talents of various brain regions to achieve a goal. The team eventually identified 39 brain regions that become active before work on a task begins, using fMRI to monitor oxygenation levels. In the present study, Dosenbach, Petersen together with Damien Fair and Bradley Schlaggar used resting state functional connectivity MRI, in which volunteers relax while being scanned rather than working on a task. They then used graph theory to map the relationships between brain regions. "A similar approach is used in the party game Six Degrees of Kevin Bacon," Petersen explains, "You use paired connections - appearances in the same movie, marital relationships - to go from one actor or actress to another until you've identified a chain of connections linking Kevin Bacon and another performer that wasn't immediately obvious." This approach identified pairs of brain regions where blood oxygen levels rose and fell roughly in synchrony that were otherwise not obvious. "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." "It's amazing," says Dosenbach, "on the one hand, the brain can be very flexible and rapidly adapt to changing feedback, but it can also lock in on something and tune out distractions until the task is finished. And these two separate control systems that work toward the same goal without actually talking to each other likely help create this powerful flexibility." As to whether the work suggests that the human brain has a split personality, Dosenbach told us that, "Our research doesn't really speak to dual personalities and the unity of consciousness. It's specific to the implementation of top-down control in how intentions and control may be implemented in the brain." The results conflict with certain conventional models but may arise naturally from studies into the emergence of the structure of complex adaptive systems. Parallels with such systems in ecology and economics suggest that multiple controllers endow complex systems with resistance to perturbations by providing redundancy on different timescales. Related links:
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The brain may have dual controls
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