Research shows brain hub activity different in coma patients

Credit: National Institute of Mental Health

(Medical Xpress)—A team of French and British researchers has found that brain region activity for coma patients is markedly different than for healthy people. In their paper published in the Proceedings of the National Academy of Sciences, the group describes the differences found when comparing fMRI scans of people in a coma with healthy volunteers.

To gain a better understanding of what goes on in the brain when a person is in a coma, and perhaps the nature of consciousness, the researchers performed fMRI brain scans on 17 people who had recently become comatose due to that led to blockage of oxygen to the brain. They then compared those scans to those taken of 20 healthy volunteers.

In analyzing the results the team found that global comparisons between the two groups revealed very few if any differences. Blood continued to flow to all of the . When focusing on the brain as a network however, they found very large differences.

To look at the brain as a network requires looking at its different parts as regions that communicate with one another, forming hubs. In healthy people, certain regions or hubs are busier than others as evidenced by more . But for the people in a coma, the team found, the normally busy hubs grew less busy, while other hubs grew busier, indicating a major change in the flow of information.

The researchers suggest that the brain scans reveal that the normally busy hubs in healthy people are centers of consciousness and their reduced role in communications in comatose patients suggests that they are most likely not conscious of their existence. They point to prior research that has suggested that being in a coma is more likely closer to the experience of being under anesthesia than being asleep. They add that the their research indicates that regions of the brain that are responsible for thought likely require more oxygen rich blood, and are thus likely to be more sensitive to oxygen deprivation than other areas of the brain, which might explain why people go into a coma when those regions are harmed.

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Imaging the network traffic in our brains

More information: Hubs of brain functional networks are radically reorganized in comatose patients, PNAS, Published online before print November 26, 2012, doi: 10.1073/pnas.1208933109

Human brain networks have topological properties in common with many other complex systems, prompting the following question: what aspects of brain network organization are critical for distinctive functional properties of the brain, such as consciousness? To address this question, we used graph theoretical methods to explore brain network topology in resting state functional MRI data acquired from 17 patients with severely impaired consciousness and 20 healthy volunteers. We found that many global network properties were conserved in comatose patients. Specifically, there was no significant abnormality of global efficiency, clustering, small-worldness, modularity, or degree distribution in the patient group. However, in every patient, we found evidence for a radical reorganization of high degree or highly efficient "hub" nodes. Cortical regions that were hubs of healthy brain networks had typically become nonhubs of comatose brain networks and vice versa. These results indicate that global topological properties of complex brain networks may be homeostatically conserved under extremely different clinical conditions and that consciousness likely depends on the anatomical location of hub nodes in human brain networks.

© 2012 Medical Xpress

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Nov 27, 2012
This seems to touch on a number of contentious issues, but what i find particularly interesting is the evidence for an 'executive network' as the seat of 'conscience' (sic), a prospect that had been thrown into doubt by recent works supporting the notion that consciousness was more a product of the degree of general connectivity rather than that of any localised faculty.

Equally fascinating is the suggestion consciousness is a particularly energy-hungry process, which throws up its own raft of questions: is the process fundamentally different from other modes of network activity - perhaps akin to a higher-level language 'wrapping around' the underlying language base? Or is it just a denser, more intensive form of the same type of global processing protocols? After all, it might reasonably be anticipated that a 'master network' would be doing less work than the net throng of disparate nuclei it corrals. Is it perhaps higher frequency activity, higher voltage, or what?

Nov 27, 2012
You're posing a lot of pertinent questions to a discipline that's by its very nature incapable of answering. Consciousness is too elusive for science because of the requirement of reproducibility. It's impossible to measure, photograph, or record with scientific instruments. All we have is our own awareness of it and its unique profile to each and every living entity. It is massless, not even the size of a pinpoint, and is unbridled at times like the neutrino. There are some subjects that science can get information from ancient knowledge, or what was then ancient science.

Nov 28, 2012
I appreciate that it appears ephemeral, ethereal, intangible, subjective - or in a word, dualistic - but this is what makes the cracks in that facade so interesting.

We can switch it on or off in a variety of ways, and increasingly, measure corresponding activity of the wetware in real-time. Likewise we can influence and modify its behaviour with drugs, electrical and magnetic simulation, and exploits like subconscious priming. Then there's all manner of optical illusions, cognitive sleight-of-hand phenomenon like change blindness, somatosensory ones like phantom appendages, and a whole smorgasbord of different aphasias. Even music, that can speak to our souls, cut us down or leave us ascendant, depends on rigorous mathematical relationships - how, and in what sense, are all factors of two of a fundamental frequency perceived as equivalent? It's a rigidly mechanical valuation, wholly objective, yet innate to the depths of our psyche...

Can it be digitised, created, transplanted?

Nov 28, 2012
Its evidently a critical information processing function, and seems increasingly to be dependent on thermodynamic criticalities - connective thresholds, charge thresholds, temporal thresholds; an edge-of-chaos dynamical system, processing information by means of exquisitely fine-tuned efficiencies... its emergent indeterminacy bounded by strongly determined physical variables.

This is the fire. Understanding, even mastering, the chemistry, won't make the dance of the flame any less mesmerising...

Nov 28, 2012
You ought to be published with writing like that. I've had the privilege of investigating the subject with first hand experience- not with drugs, but through meditation. A few sessions resulted in the "separation" of my "consciousness" from my physical body, also known as an "out-of-body experience." When it happens, there is little doubt that it's the most profound of all experiences. I suggest you read some first-hand accounts from people in all cultures and time periods. Then pursue the experience yourself if you're so inclined.

Nov 29, 2012
lol for 'out of body experiences' i look no further than some of the things i was mis-sold as E in my youth, but i've dabbled in meditation too - i wouldn't describe the results as disassociative though; the whole exercise was uninterrupted sensory focus. But i was always a determinist, never a dualist, so i guess that shaped my experiences...

Cheers for the nod, however the type of 'out of body experience' i've been considering lately is mind imaging - the fruits of endeavours like the Human Connectome Project and developments in autonomous networks - the possibility of rendering mind in software... for writing, with mind-software transplants as a starting point you quickly end up with a universe that makes The Matrix look tame - real and virtual worlds in parallel, both populated by organics, ex-organics & synthetics alike, inter-dependent, yet with vastly different & often conflicting restrictions and needs... recipe for a plot line from hell eh? If only i had the time..

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