It's usually easy to spot when someone is aware. However, there are many tragic cases in which it is unclear whether a person who is unresponsive to a serious brain injury is really no longer conscious. This ambiguity can raise ethical questions about how to manage or end the life-sustaining care of such a person.
A new study on Wednesday does not provide clear answers to these questions, but their findings may someday objectively help us to objectively track the consciousness of unresponsive people through their patterns of brain activity. There may even be an indication of better treatments that can bring some of these people back to consciousness of unconsciousness.
The study published in Science Advances was a collaboration between researchers from France, Belgium, the United Kingdom, the United States and other countries. and Canada. Together they recorded the brain activity (via functional MRI) of 1
There were 47 healthy volunteers whose brain was sedated while awake and after transient general anesthesia. The remaining 112 people all had a severe brain injury and were further divided into two groups. It was assumed that some were in a minimally conscious state, which meant that they were able to show possible flicker of consciousness. Others have been diagnosed with an unresponsive wakefulness syndrome, a condition in which people can be awake without showing signs of voluntary movement (this is commonly referred to as the vegetative state).
Interestingly, some of these unresponsive individuals (in the UK) had tested positive for mental imaging, where their brain showed activity while being asked to just imagine something, such as moving the hand.
The researchers then compared the scans of each group. Based on the fMRI results, they found four different patterns of neuronal activity, which are believed to be related to the perception in the patient's brain. The patterns differed by their levels of complex, long-range connections between neurons in 42 different brain regions along a spectrum from the most to the least complex and connected.
The highly complex pattern 1 they found was most likely to be found in fully awakened healthy volunteers, while the least complex pattern, pattern 4, was the most common in patients without response (patterns 2 and 3 showed the same frequency in all groups). However, people in a minimally conscious state also showed pattern 1 more frequently than people in a vegetative state.
People who were vegetative but responded to the mental imaging test occasionally also displayed the complex pattern 1, indicating that they could have had fleeting moments of consciousness. In vegetative patients who did not respond to the mental imaging test and in healthy subjects who were sedated, there was virtually no sign of the pattern.
All these subtle differences, according to the authors, could mean that there are ways to distinguish the most unconscious from the totally unconscious.
"This complex pattern disappeared with deep anesthesia of the patients and confirmed that our methods actually respond to the patient's level of consciousness rather than their overall brain damage or external brain damage," said study author Davinia Fernández-Espejo. a neuroscientist at the University of Biringham in the UK, in an article for The Conversation in which he explained the work of the team.
Fernández-Espejo and her team's research should be considered as one of her team's researches Getting Started in Many Needed to Identify Cognitive Marks in the Brain. Such a discovery would obviously be great to help physicians and families of autonomic patients better understand their situation. However, this could have even greater effects.
"In the future, it may be possible to develop ways to externally modulate these deliberate signatures and restore some degree of awareness or responsiveness to patients who have lost them, such as through noninvasive brain stimulation techniques such as the transcranial Electrical stimulation, "said Fernández-Espejo. According to Fernández-Espejo, this research is something her team is already working on.
Apart from these unfortunate patients, she added, this type of research could be expanded to learn more about the brain states of people undergoing psychedelics and those who say they might have a lucid dream.
[Science Advances, The Conversation]