Our brains produce more entropy when we are awake than when we are asleep. The finding could lead to better ways to measure the consciousness of people who appear to be in a coma.
Entropy is a measure of disorder and in our universe, everything tends to move from less disorder to more over time. For instance, breaking a coffee cup increases entropy. While this breaking can happen in many ways, you never see a broken cup spontaneously re-assemble itself and therefore decrease its entropy.
Electrical signals in our brains can also produce entropy as part of processing and transmitting information, such as the visual signals from our eyes. at the Paris-Saclay University in France and his colleagues wanted to determine whether our brains produce more entropy when we are awake or when we are asleep.
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The researchers used functional magnetic resonance imaging (fMRI) to scan the brains of 15 people in different states of consciousness: while each person was awake and in three stages of sleep, from light to very deep.
To calculate entropy, the team used a model that was previously developed from studying the pathways that electrical signals can follow inside of the brain. The different routes help reveal the different processes they can carry out, and each of those processes produces different amounts of entropy. From this, the researchers calculated entropy production for each person in each state of consciousness. They found that it decreased as people fell deeper into sleep. In the state of deepest sleep, people鈥檚 brains, on average, produced 25 per cent less entropy than when they were awake.
Cofr茅 says that this gives researchers a way to quantify consciousness 鈥� a person whose brain shows the same amount of entropy production in an fMRI study as someone who is deeply asleep is likely to have the same types of processes happening in their brain and to be at a similar level of consciousness, he says. The new method could then potentially be used to quantify the consciousness of people in comas or eventually help to diagnose people with locked-in syndrome, who are conscious but unable to communicate with the external world, says Cofr茅.
Previous research has linked consciousness to entropy. Some , for example, have indicated that states of very altered consciousness, such as those induced by psychedelic substances like psilocybin, result in an increase in entropy of the brain itself 鈥� meaning that it is harder to predict its overall electrical state 鈥� and not just the entropy different signals produce.
at Trinity College in Connecticut says that understanding the state of awareness of people that are minimally conscious has long been an area of study. However, it is not yet clear that entropy production is an unambiguous mark of consciousness.
For example, dreams can happen in deep sleep 鈥� a time of low entropy 鈥撀� but they reflect 鈥渁 high level of consciousness鈥�, says Lloyd. As such, dreams could actually increase entropy production in the brain, but the study didn鈥檛 consider this, he says.
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