Across vast distances, galaxies are organized in a structure of filaments, nodes, and voids collectively known as the cosmic web. Inside our brain, neurons are also organized in a network of filaments and nodes. This similarity has long spiked the curiosity of scientists, artists, and the general public. Now, new research published in Frontiers in Physics shows the two systems are a lot more similar than we thought.
Two Italian researchers, an astrophysicist and a neurosurgeon, set out to see if the visual similarities had a deeper connection. Neurons and galaxies are vastly different systems that self-organize into large structures, which the team’s research suggests are shaped by similar underlying principles. The work does not claim we have a universe in our skull or that the cosmos is a giant brain. Instead, it focuses on the properties of network dynamics.
Most of the links between the brain and the cosmos are just coincidences. The average brain has 69 billion neurons. For a long time, the estimate for the number of galaxies in the universe was 100 billion, but it is now estimated to be 20 times larger. Around 77 percent of the mass of the brain is water. Around 70 percent of the energy-matter content of the universe is dark energy.
But given they look similar, do the networks build up in the same way? The researchers think so. In astronomy, scientists are used to calculating the power spectrum of the cosmic web — a mathematical technique that provides an understanding of how galaxies are distributed in space. Applying the same technique to the brain is far from easy. The team had to simplify the problem somewhat. They didn’t track the detailed connections between neurons but instead tracked their proximity.
Taking into account the limitations, the researchers found that the neural network of the cerebellum on a scale between 1 and 100 microns is organized in a similar way to the cosmic web on a scale between 5 million and 500 million light-years.
The finding is certainly intriguing. Despite the dramatically different scales and the different physical forces shaping the networks, they organize in a similar way. The next question is how does this happen? We don’t have an answer for that yet.
Both the universe and our brain remain mysterious. The standard model of cosmology has many uncertainties, such as what is dark matter and dark energy. When it comes to the brain, we are only now increasing our understanding of how connections are formed (and their trade-offs) and how the neural network evolves as a whole.
"In the brain, we have a very good knowledge of the physical/chemical mechanisms underlying the formation of networks. We know how a connection between two neurons works (fire together, wire together) and we know how these connections interact when there are more than two neurons (oscillations/firing rate synchronicity)," neuroscientist Dr Steven Di Costa, who was not involved in the study, told IFLScience.
"I think we struggle more with what exactly that means. How does this setup contribute to the complexity of human behavior?"
New data on both the brain and the universe is needed to fully understand how networks such as these form in the first place.