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Humans have learned to travel in space, to eradicate diseases and to understand nature at a breathtaking level of fundamental particles.
Yet we have no idea how our consciousness – our ability to experience and learn the world in this way and relate it to others – arises in the brain.
In fact, while scientists have been concerned with the understanding of consciousness for centuries, it remains one of the most important unanswered questions of modern neuroscience.
Now our new study, published in Progress of science, brings to light the mystery by discovering the networks of the brain that work when we are aware.
This is not just a philosophical question. Determining whether a patient is "conscious" after suffering a serious brain injury is a significant challenge for physicians and families who need to make care decisions.
Modern brain imaging techniques are beginning to lift this uncertainty, giving us unprecedented insights into human consciousness.
For example, we know that complex brain areas, including the prefrontal cortex or precuneus, responsible for a range of higher cognitive functions, are generally involved in conscious thinking.
However, large areas of the brain do a lot of things. We wanted to know how consciousness is represented in the brain at the level of specific networks.
The reason it is so difficult to study conscious experiences is that they are entirely internal and that others can not access them.
For example, we can both look at the same image on our screens, but I have no way of saying whether my experience seeing it is similar to yours, unless you talk to me about it. .
Only conscious people can make subjective experiences and therefore the most direct way to determine if a person is conscious is to ask them to talk to us about it.
But what would happen if you lost your ability to speak? In this case, I could still ask you a few questions and you could perhaps sign your answers, for example by shaking your head or moving your hand.
Of course, the information that I would get in this way would not be as rich, but it would be enough for me to know that you do have experiences.
If however you could not produce answers, I would have no way of knowing if you are aware and would badume that you are not.
Network search
Our new study, a collaboration of seven countries, identified brain signatures that could indicate a conscience without relying on self-evaluation or the need to ask patients to engage in a particular task, and to differentiate conscious and unconscious patients after injury.
When the brain is badly damaged, for example during a serious road accident, people can end up in a coma. It is a condition in which you lose your ability to be awake and aware of your environment and need mechanical support to breathe.
This does not usually last more than a few days. After that, patients sometimes wake up but show no evidence of awareness of their consciousness or that of the world around them – this is known as a "vegetative state".
Another possibility is that they present only evidence of a very minimal awareness – called minimal consciousness state. For most patients, this means that their brain always perceives things but they do not experience them.
However, a small percentage of these patients are indeed conscious, but simply unable to produce behavioral responses.
FMRI scanner (semi-conscious / Wikipedia / public domain)
We used a technique known as functional magnetic resonance imaging (fMRI), which allows us to measure brain activity and how certain regions "communicate" with each other.
In particular, when a brain region is more active, it consumes more oxygen and needs a larger amount of blood to meet its needs.
We can detect these changes even when participants are resting and measuring variations from one region to another to create patterns of connectivity across the brain.
We used the method on 53 patients in the vegetative state, 59 people in the state of minimum consciousness and 47 participants in good health. They came from hospitals in Paris, Liege, New York, London and Ontario.
Patients in Paris, Liege and New York were diagnosed through standardized behavioral badessments, such as the need to move their hands or blink.
In contrast, London patients were badessed using other advanced brain imaging techniques, which required the patient to modulate his brain to produce neuronal responses instead of external physical responses. like imagine moving your hand instead of moving it.
(Tagliazucchi et al., 2019)
We found two main models of communication between regions. Simply reflected the physical connections of the brain, such as communication only between pairs of regions having a direct physical connection to each other.
This has been observed in patients with virtually no conscious experience.
One of them represented very complex dynamic brain-scale interactions in 42 brain regions belonging to six brain networks that play an important role in cognition (see image below). above). This complex pattern was almost exclusively present in people with a certain level of consciousness.
Importantly, this complex pattern disappeared when the patients were under deep anesthesia, confirming that our methods were indeed sensitive to the level of consciousness of the patients and not to their general brain lesions or their external reactivity.
Research like this can potentially help to understand how objective biomarkers can play a crucial role in medical decision-making.
In the future, it may be possible to develop ways to externally modulate these conscious signatures and restore some degree of consciousness or responsiveness in patients who have lost them, for example by using stimulation techniques. non-invasive cerebral palsy such as transcranial electrical stimulation.
Indeed, in my research group at the University of Birmingham, we begin to explore this path.
It is interesting to note that research also leads us to understand how consciousness develops in the brain.
With more data on the neural signatures of consciousness in people with different states of consciousness altered – from psychedelic to lucid dreams – we can one day solve the problem.
Davinia Fernández-Espejo, Lecturer at the Faculty of Psychology and Center for Human Brain Health at the University of Birmingham.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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