Consciousness may be the product of carefully balanced chaos | Science | AAAS
'Is my yellow the same as your yellow? Does your pain feel like my pain? The question of whether the human consciousness is subjective or objective is largely philosophical. But the line between consciousness and unconsciousness is a bit easier to measure. In a new study of how anesthetic drugs affect the brain, researchers suggest that our experience of reality is the product of a delicate balance of connectivity between neurons—too much or too little and consciousness slips away.
In order to look for the signature of consciousness in the brain, Tagliazucchi and his colleagues used a drug called propofol—an anesthetic drug used in surgery—to induce loss of consciousness in participants while they were inside an fMRI machine’s scanner. fMRI works by tracking blood flow in the brain, which can be used as a real-time proxy for electrical activity when neurons fire. The team recorded data from 12 participants in states of wakefulness, ongoing sedation, unconsciousness, and recovery.
The results, published online today in the Journal of the Royal Society Interface, show that brain activity varies widely between conscious and unconscious states. The difference may come down to how the brain “explores the space of its own possible configurations,” Tagliazucchi says.'http://www.sciencemag.org/news/2016/01/consciousness-may-be-product-carefully-balanced-chaosLarge-scale signatures of unconsciousness are consistent with a departure from critical dynamics | Journal of The Royal Society Interface
Loss of cortical integration and changes in the dynamics of electrophysiological brain signals characterize the transition from wakefulness towards unconsciousness. In this study, we arrive at a basic model explaining these observations based on the theory of phase transitions in complex systems. We studied the link between spatial and temporal correlations of large-scale brain activity recorded with functional magnetic resonance imaging during wakefulness, propofol-induced sedation and loss of consciousness and during the subsequent recovery. We observed that during unconsciousness activity in frontothalamic regions exhibited a reduction of long-range temporal correlations and a departure of functional connectivity from anatomical constraints. A model of a system exhibiting a phase transition reproduced our findings, as well as the diminished sensitivity of the cortex to external perturbations during unconsciousness. This framework unifies different observations about brain activity during unconsciousness and predicts that the principles we identified are universal and independent from its causes.