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Make Assurance Double Sure ? Dual Networks for Behavioral Control
9 Jul, 2007 02:01 pm
The ability to exercise voluntary control over one?s own actions forms a central aspect of what it means to be human. The number of possible responses we can produce to a given stimulus is essentially infinite. For example, dependent on someone?s internal goals, a stimulus such as ?word? could be read silently or aloud, spelled forwards or backwards, copied, translated into a foreign language or completely ignored, and so forth. How the human brain achieves this level of behavioral control has been of great interest to neuroscientists for some time. It is thought that parts of the brain function as controllers by influencing processing in other parts of the brain more closely related to sensation (input) and movement (output).
Previous models of ‘cognitive control’ ascribed such voluntary behavioral control functions to a limited unitary control system proposed to be located in the most frontal parts of the brain. However, recent research carried out at Washington University in St. Louis using a range of modern neuroimaging techniques paints a different picture. Studies by first author Nico Dosenbach, Damien Fair, Bradley Schlaggar, Marcus Raichle, senior author Steven Petersen, and collaborators, indicate that about two dozen different brain regions play important roles in the control of goal-oriented behavior. In addition, these control regions appear to organize into separate networks each with specific network architectures. According to the most recent data, humans seem to possess not one, but at least two large-scale brain networks dedicated to controlling other parts of the brain and, through them, behavior.
Surprisingly the brain’s two control networks (termed the fronto-parietal and cingulo-opercular networks) seem to operate fairly independently of each other. One of the networks (fronto-parietal) seems to initiate new tasks and adjust control settings in real-time (moment-to-moment) based on feedback signals, such as information about errors, for example. The second control network (cingulo-opercular) also receives feedback signals, yet it seems to implement a more stable, integrative form of control. Its hallmark feature appears to be the long-term maintenance of one’s internal goals even in the face of distracting sensory inputs.
This type of control network architecture is quite consistent with theories about the structure of “complex adaptive” large-scale systems. For example, ecological and economical systems are both resistant to perturbations, yet rapidly adaptive. These systems often have multiple controlling variables, or controllers, that act via different mechanisms and often over different time scales. A simple physiologic example for such control architecture would be balance, which is supported by the inner ear, joint position sensors and the visual system. Having multiple controllers increases a system’s resilience to damage.
As humans, we may be able to rapidly exploit new environmental opportunities, as well as stubbornly focus on a specific task despite distraction, precisely because our brain possesses separate rapid-acting and stable maintenance control networks.
Dosenbach, N. U., D. A. Fair, et al. (2007). "Distinct brain networks for adaptive and stable task control in humans." Proc Natl Acad Sci U S A 104(26): 11073-8.
Dosenbach, N. U., K. M. Visscher, et al. (2006). "A core system for the implementation of task sets." Neuron 50(5): 799-812.