Virtual chaos: The internal dynamics of human brains leave them poised on the edges of a transition.
Credit: iStockphoto
SYDNEY: The human brain functions at a critical transition point between randomness and order, allowing the brain to quickly switch between mental states, say Cambridge researchers.
The study builds upon a model that suggests the human brain operates in a self-organised critical state, which means that brain networks can undergo rapid reconfigurations in anatomical shape in response to only small changes in external environments.
"Self-organised criticality is intuitively attractive as a model for brain functions such as perception and action, because it would allow us to switch quickly between mental states in order to respond to changing environmental conditions," said University of Cambridge neuroscientist Manfred Kitzbichler, whose work was published Friday in PLoS Computational Biology.
Criticality in systems
To reach a critical transition point in most systems, there needs to be parameter that changes. When a system changes from a liquid to a solid, for example, it is because of a temperature change.
In self-organised critical state, however, abrupt changes can occur "merely on the basis of a system's own internal lawful processes," explained Gerhard Werner, a biomedical engineer at the University of Texas at Austin who has studied criticality in the brain but was not part of the study.
Self-organised criticality can emerge from interactions in many different physical systems, including avalanches, earthquakes and heartbeat rhythms. In addition, computational networks showing these characteristics have optimal data storage and information-processing capacity. These qualities made self-organised criticality an attractive model for brain dynamics, though it has remained only a theoretical model until now.
Critical dynamics in the brain
For the study, the researchers used brain-imaging techniques to measure changes in the synchronisation of activity between regions of the brain. The pattern they saw is indicative of self-organised criticality. They then looked at the synchronisation of activity in computational models, finding that the brain's activity exactly reflected that of the models in a self-organised critical state.
Werner said this research provides important insight into the brain. "The article is of great interest and addresses novel approaches to conceptualise brain function," he said.
"These results are the first clear evidence that human brain networks exist in a self-organised critical state," said co-author and University of Cambridge psychiatrist Ed Bullmore.
Bullmore added that the researchers are now investigating how critical dynamics in brain networks relate to impairments in cognitive function.
Consciousness and Chaos
Wonder how consciousness needs criticality? Maybe it needs such a labile brain dynamics so it can 'tweak' it from one state to the next - and visa versa. Physicalist Interactionism.