This Big Think article came across my Facebook feed, suggesting that higher entropy in the brain is correlated with consciousness. The article was a bit overexcited, though, saying this would, if proven true, “change the face of physics”. And, misleadingly, it seemed to be conflating the results of this study with entropy in thermodynamics. The laws of thermodynamics talk about how entropy increases over time in a physical system. This study doesn’t seem to be about how entropy changes over time, but about how (they think) levels of entropy in the brain correlate to degrees of consciousness.
The Big Think article links to this one in Physics World, which is more down to earth and somewhat more clear, but I still felt the need to write this post to summarize it and break it down a little more.
One thing that can cause confusion is that the word ‘entropy’ is used to talk about different things. There’s a mathematical definition I don’t understand, but colloquially it means “the number of possible meaningless rearrangements” of something. In a messy room (higher entropy), you could move a bunch of stuff around and it would still be the same level of messy. But in a tidy room (low entropy), everything’s in its place, so if you move anything it’s no longer as tidy. If you wanted a really high entropy room, you could put all your stuff into a blender and then spread it around evenly. You could move this mixture around arbitrarily, and you wouldn’t be able to distinguish that this part came from a blanket, that part came from a book, etc.
Take that understanding of entropy and apply it to the set of connections between neurons in the brain:
Ramon Guevarra Erra, a physicist at the Paris Descartes University, points out that there is only one way to connect each set of neurons in a network with every other set, just as there is only one way to have no connections at all. In contrast, he notes, there are many different ways that an intermediate medium-sized number of connections can be arranged.
Here’s the meat:
Jose Luis Perez Velazquez, a biochemist at the University of Toronto, and colleagues hypothesized that what is maximized during consciousness is not connectivity itself but the number of different ways that a certain degree of connectivity can be achieved.
And:
The latest work stems from the observation that consciousness, or at least the proper functioning of brains, is associated not with high or even low degrees of synchronicity between neurons but by middling amounts.
So, medium levels of connectivity/synchronization between parts of the brain have the highest entropy, and were also observed to have higher degrees of consciousness:
In both cases, the bottom line was the same: subjects’ brains display higher entropy […] when in a fully conscious state.
This is just me speculating, but it sounds like this may be related to Integrated Information Theory, which posits that consciousness is related to the level of integration of information. In information theory (a branch of math, not to be confused with IIT, a theory of consciousness), information is measured in… wait for it… entropy.
It may be too early to get our hopes up about this research. Guevara Erra admits these results are “not watertight” and “very heterogenous, and the study was only done on 8 patients. However:
he nevertheless remains “highly confident” that the correlations they have identified are real, particularly, he argues, because they were seen in “two very different sets of data”.