Max
08-21-2002, 11:32 AM
http://www.pnas.org/cgi/content/abstract/99/17/10948
Transitions between dynamical states of differing stability in the human brain
Andreas Meyer-Lindenberg*,, Ulf Ziemann,§, Göran Hajak*, Leonardo Cohen, and Karen Faith Berman*
* Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, and Human Cortical Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
Edited by Nancy J. Kopell, Boston University, Boston, MA, and approved June 20, 2002 (received for review February 26, 2002)
What mechanisms underlie the flexible formation, adaptation, synchronization, and dissolution of large-scale neural assemblies from the 1010 densely interconnected, continuously active neurons of the human brain? Nonlinear dynamics provides a unifying perspective on self-organization. It shows that the emergence of patterns in open, nonequilibrium systems is governed by their stability in response to small disturbances and predicts macroscopic transitions between patterns of differing stability. Here, we directly demonstrate that such transitions can be elicited in the human brain by interference at the neural level. As a probe, we used a classic motor coordination paradigm exhibiting well described movement states of differing stability. Functional neuroimaging identified premotor (PMA) and supplementary motor (SMA) cortices as having neural activity linked to the degree of behavioral instability. These regions then were transiently disturbed with graded transcranial magnetic stimulation, which caused sustained and macroscopic behavioral transitions from the less stable out-of-phase to the stable in-phase movement, whereas the stable pattern could not be affected. Moreover, the strength of the disturbance needed (a measure of neural stability) was linked to the degree of behavioral stability, demonstrating the applicability of nonlinear system theory as a powerful predictor of the dynamical repertoire of the human brain.
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To whom reprint requests should be addressed at: Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, 10-4C101, 9000 Rockville Pike, Bethesda, MD 20892-1365. E-mail: andreasml@nih.gov.
§ Present address: Clinic of Neurology, J. W. Goethe University of Frankfurt, 60590 Frankfurt am Main, Germany.
www.pnas.org/cgi/doi/10.1073/pnas.162114799 (http://www.pnas.org/cgi/doi/10.1073/pnas.162114799)
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"With every scientific advance, we grow closer to unlocking the mysteries of life and creation. But what have we gained if in the process, we lose our humanity. The most powerful thing we pass along to our children may not reside in the genes, but in the soul."
The Outer Limits(Criminal Nature)
[This message was edited by Wise Young on Aug 22, 2002 at 08:39 AM.]
[This message was edited by Wise Young on Aug 22, 2002 at 08:40 AM.]
Transitions between dynamical states of differing stability in the human brain
Andreas Meyer-Lindenberg*,, Ulf Ziemann,§, Göran Hajak*, Leonardo Cohen, and Karen Faith Berman*
* Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, and Human Cortical Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
Edited by Nancy J. Kopell, Boston University, Boston, MA, and approved June 20, 2002 (received for review February 26, 2002)
What mechanisms underlie the flexible formation, adaptation, synchronization, and dissolution of large-scale neural assemblies from the 1010 densely interconnected, continuously active neurons of the human brain? Nonlinear dynamics provides a unifying perspective on self-organization. It shows that the emergence of patterns in open, nonequilibrium systems is governed by their stability in response to small disturbances and predicts macroscopic transitions between patterns of differing stability. Here, we directly demonstrate that such transitions can be elicited in the human brain by interference at the neural level. As a probe, we used a classic motor coordination paradigm exhibiting well described movement states of differing stability. Functional neuroimaging identified premotor (PMA) and supplementary motor (SMA) cortices as having neural activity linked to the degree of behavioral instability. These regions then were transiently disturbed with graded transcranial magnetic stimulation, which caused sustained and macroscopic behavioral transitions from the less stable out-of-phase to the stable in-phase movement, whereas the stable pattern could not be affected. Moreover, the strength of the disturbance needed (a measure of neural stability) was linked to the degree of behavioral stability, demonstrating the applicability of nonlinear system theory as a powerful predictor of the dynamical repertoire of the human brain.
--------------------------------------------------------------------------------
To whom reprint requests should be addressed at: Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, 10-4C101, 9000 Rockville Pike, Bethesda, MD 20892-1365. E-mail: andreasml@nih.gov.
§ Present address: Clinic of Neurology, J. W. Goethe University of Frankfurt, 60590 Frankfurt am Main, Germany.
www.pnas.org/cgi/doi/10.1073/pnas.162114799 (http://www.pnas.org/cgi/doi/10.1073/pnas.162114799)
==============================
"With every scientific advance, we grow closer to unlocking the mysteries of life and creation. But what have we gained if in the process, we lose our humanity. The most powerful thing we pass along to our children may not reside in the genes, but in the soul."
The Outer Limits(Criminal Nature)
[This message was edited by Wise Young on Aug 22, 2002 at 08:39 AM.]
[This message was edited by Wise Young on Aug 22, 2002 at 08:40 AM.]