In a nutshell: Tests in fruit flies show that “informational structures” of the brain could be used to measure levels of consciousness.

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How consciousness is generated by the brain is a longstanding question in neuroscience. One theory – known as integrated information theory (IIT) – proposes that conscious experience corresponds to organised patterns of interactions between cells in the brain. The brain cells must be involved in both feedforward and feedback mechanisms – affecting, and being affected by, other cells in the brain, respectively.

Based on these patterns, IIT describes informational structures in the brain. These structures capture the information that the brain itself can access. More sophisticated structures would be linked to higher levels of consciousness.

Although IIT offers a compelling explanation of consciousness, it has not been tested in many experiments.

To test whether IIT can indeed capture and quantify levels of consciousness, Brain Function CoEresearchers conducted experiments on the fruit fly (Drosophila melanogaster). The international research team was led by PhD student Angus Leung and his supervisor, Naotsugu Tsuchiya, from Monash University.

Fruit flies have relatively simple brains compared with those of humans. Like humans, these flies can experience various states of arousal, ranging from active wakefulness to sleep. Unlike humans, however, fruit flies may react to sensory inputs and generate movement through feedforward, reflex-like mechanisms in the brain. If this were the case, fly brains should produce no integrated information, and thus have minimal informational structures.

The researchers analysed detailed recordings of brain activity in the fruit fly that had been collected when the flies were awake or anaesthetised. They used computational methods to determine the informational structures of the fly brain during these two states.

Unexpectedly, the team found rich informational structures across the fly brain that could not arise from purely feedforward mechanisms. Furthermore, these structures were present during wakefulness, but absent under anaesthesia.

This study does not prove whether flies are truly conscious or not. However, it does challenge the feedforward view of the fly brain. It also shows that informational structures could potentially be used to measure consciousness.

Next steps:
The researchers plan to apply IIT in more complex brains, such as the rat brain and the human brain. They are also interested in using IIT to study the timescales involved in generating conscious experience in the brain.

Leung, A., Cohen, D., van Swinderen, B., & Tsuchiya, N. (2021). Integrated information structure collapses with anesthetic loss of conscious arousal in Drosophila melanogaster. PLOS Computational Biology, e1008722. doi: 10.1371/journal.pcbi.1008722

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