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A new study will contribute to the problem of defining human consciousness. In most cases, a conscious or unconscious person is easy to diagnose. However, there are some cases that, usually after a serious brain injury, where it is difficult to tell if an unresponsive person is no longer truly conscious.
The diagnosis of someone's consciousness can be a matter of life or death when the answer has implications for the type of ongoing care they receive. A new collaborative study gathered brain activity data via functional MRI from the 150 different people at four different locations.
Subtle responses make a massive difference
Each of the subjects was technically unconscious but not all in the same way. 47 of the healthy subjects had their brains scanned when both awake and after being placed under general anesthesia.
The remaining 112 volunteers had all suffered a serious brain injury. This larger group was then further divided into a group considered to be in a minimally conscious state and a group diagnosed with unresponsive wakefulness syndrome.
The minimally conscious group were capable of showing small signs of awareness while the unresponsive syndrome group had subjects that were awake but showed no sign of voluntary movement. The results of all of the brain scan data were then compared.
Clear patterns emerge from data comparison
Based on the fMRI results four clear patterns of brain activity emerged that is thought to be related to cognition. The patterns are noted by the levels of complex connections between neurons in 42 different brain regions; they are formed along a spectrum of most to least complex.
The scientist noted that the most highly complex pattern 1, was more likely to show up in the healthy awake patients. The least complex pattern 4, was common in completely unresponsive patients.
The middle patterns 2 and 3 showed up with the same frequency across all groups. However, the minimally conscious group exhibited pattern 1 more than in completely unresponsive patients.
Consciousness definition requires attention to the subtle
The researchers were interested to note that the people in the minimally responsive or vegetative state who did respond to mental imaging also occasionally showed pattern 1. Patients in a vegetative state that did not respond to mental imaging did not display signs of pattern 1.
Nor was this pattern found in the healthy volunteers who were sedated.
“Importantly, this complex pattern disappeared when patients were under deep anesthesia, confirming that our methods were indeed sensitive to the patients’ level of consciousness and not their general brain damage or external responsiveness,” study author Davinia Fernández-Espejo, a neuroscientist at the University of Birmingham in the UK, said in an article for The Conversation explaining the team’s work.
Research offers further opportunity for study
The authors say, while there is still no definitive answer, careful understandings of the subtle distinctions between the patterns and groups definitely provides new opportunities to study the definition of consciousness.
“In the future, it might be possible to develop ways to externally modulate these conscious signatures and restore some degree of awareness or responsiveness in patients who have lost them, for example by using non-invasive brain stimulation techniques such as transcranial electrical stimulation,” said Fernández-Espejo.