In a nutshell: A new approach based on statistical modelling suggests that brain activity alone could be used to determine levels of consciousness.

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Brain activity is closely linked to consciousness. A person in a deep coma, for example, has less brain activity than someone who is fully awake.

But matching the amount of brain activity to the level of consciousness is difficult. Several techniques, including electroencephalography (EEG) and functional magnetic resonance imaging (MRI), can measure brain activity. But additional information, such as signs of how a person reacts to certain stimuli, is needed to determine the level of consciousness. That’s not always possible, for example for people in an unconscious vegetative state.

To develop a more accurate method of determining the level of consciousness, a research team involving Brain Function CoE researcher Naotsugu Tsuchiya at Monash University combined computational and statistical modelling methods.

The team, led by PhD student Roberto Muñoz from Kavan Modi’s group at Monash University, recorded brain activity in fruit flies over time. Activity was recorded for 18 seconds while the flies were awake and then for another 18 seconds after they had been anaesthetised. The researchers then analysed these recordings – known as time series – to see how they reflected the different states of consciousness.

They found that brain activity was more complex when a fly was awake than when it was under general anaesthesia.

The researchers also analysed the time series in reverse, to see if that changed the outcome. They found that the difference in complexity between the forward and reverse analyses was less under anaesthesia. This suggests that the activity of anaesthetised brains becomes less structured and more random.

Based on these findings, the researchers determined that brain activity can be described in terms of past and future relationships. In other words, how a group of brain cells will react at any given moment depends on its activity in the past.

This work suggests that these past and future relationships alone could be used to accurately measure levels of consciousness. This has important implications for neuroscience research involving animals – and perhaps eventually for human health and medical treatment.

Next steps:
The researchers are planning to investigate whether they can apply the same approach to other animals, humans and brain states.

Muñoz, R. N., Leung, A., Zecevik, A., Pollock, F. A., Cohen, D., van Swinderen, B., Tsuchiya, N., & Modi, K. (2020). General anesthesia reduces complexity and temporal asymmetry of the informational structures derived from neural recordings in Drosophila. Physical Review Research 2, 023219. doi: 10.1103/PhysRevResearch.2.023219

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