Christof Koch, a leading researcher on consciousness and the human brain, has famously called the brain "the most complex object in the known universe." It’s not hard to see why this might be true. With a hundred billion neurons and a hundred trillion connections, the brain is a dizzyingly complex object.

But there are plenty of other complicated objects in the universe. For example, galaxies can group into enormous structures (called clusters, superclusters, and filaments) that stretch for hundreds of millions of light-years. The boundary between these structures and neighboring stretches of empty space called cosmic voids can be extremely complex.1 Gravity accelerates matter at these boundaries to speeds of thousands of kilometers per second, creating shock waves and turbulence in intergalactic gases. We have predicted that the void-filament boundary is one of the most complex volumes of the universe, as measured by the number of bits of information it takes to describe it.

This can get us to thinking: Is there a similarity between the Neuron and Galaxy Networks?

The task of comparing brains and clusters of galaxies is a difficult one. For one thing it requires dealing with data obtained in drastically different ways: telescopes and numerical simulations on the one hand, electron microscopy, immunohistochemistry, and functional magnetic resonance on the other.

The human brain is composed of a large number of neurons that are interconnected in a very complicated manner. On the other hand, the universe is the very basis of all life and comprises several billion galaxies. And now scientists have found a striking similarity between the two.

In a study, Franco Vazza (astrophysicist at the University of Bologna) and Alberto Feletti (neurosurgeon at the University of Verona) investigated the similarities between them and the network of neuronal cells in the human brain. They found that the complex web of neurons in the brain looks strangely similar to the cosmic network of galaxies. Despite being incomparable in terms of size, our brain and the universe display similar kinds of organization and complexity.

The two researchers have given their arguments in a paper published in the journal Frontiers in Physics. They studied the "structural, morphological, network properties and the memory capacity of these two fascinating systems, with a quantitative approach". The "tantalizing" results show that both the complex systems demonstrate self-organization that is likely being shaped by "similar principles of network dynamics, despite the radically different scales and processes at play".

The brain has approximately 69 billion neurons whereas the observable universe can count upon a cosmic web of at least 100 billion galaxies. Apart from the apparent image of the human brain and the universe that look similar in terms of the neural and galaxies’ network, both the neurons and the galaxies make up for only 30 percent of the total mass of their respective systems. While water makes up for about 70 percent of the mass of our brain, only 30 percent of the universe is visible and the rest is dark matter.

The researchers calculated the spectral density of both systems. The results showed that the distribution of the fluctuation in both the systems followed the same progression but on different levels, Franco Vazza said in a press release. They also calculated the average number of connections in each node and the tendency of clustering several connections in relevant central nodes within the network and once again found "unexpected agreement levels".

Alberto Feletti added that these two complex networks have shown "more similarities than those shared between the cosmic web and a galaxy or a neuronal network and the inside of a neuronal body".

Despite the considerable difference in scale between the two networks, their quantitative analysis, which sits at the crossroads of cosmology and neurosurgery, recommends that different physical processes can build structures characterized by similar levels of complexity self-organization.

The human brain is a complex temporally and spatially multiscale structure in which cellular, molecular, and neuronal phenomena coexist. It can be modeled as a hierarchical network, in which neurons cluster into circuits, columns, and different interconnected functional areas.

The Universe, on the other hand, is composed of a cosmic web of at least 100 billion galaxies.

Within both systems, only 30% of their masses are composed of galaxies and neurons. Within both systems, galaxies and neurons arrange themselves in long filaments or nodes between the filaments.

Finally, within both systems, 70% of mass or energy distribution comprises components playing a passive role: water in the brain and dark energy in the observable Universe.

From the shared features of the two systems, analysts compared a simulation of the galaxies to sections of the cerebral cortex and the cerebellum. The goal was to see how matter fluctuations scatter over such different scales.

Franco Vazza said, "We calculated the spectral density of both systems. This is a technique often employed in cosmology for studying the spatial distribution of galaxies. Our analysis showed that the distribution of the fluctuation within the cerebellum neuronal network on a scale from 1 micrometer to 0.1 millimeters follows the same progression of the distribution of matter in the cosmic web but, of course, on a larger scale that goes from 5 million to 500 million light-years."

Scientists also calculated other parameters that characterize both the neuronal network and the cosmic web: the average number of connections in each node and the tendency of clustering several links in relevant central nodes within the system.

Alberto Feletti said, "Once again, structural parameters have identified unexpected agreement levels. Probably, the connectivity within the two networks evolves following similar physical principles, despite the striking and obvious difference between the physical powers regulating galaxies and neurons. These two complex networks show more similarities than those shared between the cosmic web and a galaxy or a neuronal network and the inside of a neuronal body."

The study results are provoking the scientists to think that new and effective analysis techniques in both fields, cosmology, and neurosurgery, will allow a superior comprehension of the routed dynamics underlying the temporal evolution of these two systems.