One of These Pictures Is the Brain, the Other is the Universe. Can You Tell Which is Which?
Hippocampal mouse neuron studded with synaptic connections (yellow), courtesy Lisa Boulanger, from https://www.eurekalert.org/multimedia/pub/81261.php. The green central cell body is ? 10µm in diameter. B. Cosmic web (Springel et al., 2005). Scale bar = 31.25 Mpc/h, or 1.4 × 1024 m. Juxtaposition inspired by Lima (2009).
A neuron in the brain juxtaposed with clusters of galaxies and their connected filaments of matter and dark matter. The resemblance is immediately clear. The implication? You may have an entire universe in your head. But the similarity between the images could simply be a case of apophenia – perceiving likeness where none actually exists. After all, how can these two things be similar given the vast difference in scale between them? But what if beyond the visual similarity between the networks of neurons in the brain and webs of galaxies in the Cosmos, an objective measurement could compare just how similar they truly are? That’s what Franco Vazza (astrophysicist at the University of Bologna) and Alberto Feletti (neurosurgeon at the University of Verona) set out to discover combining both their disciplines for a publication in “Frontiers of Physics.”
An Intergalactic Link
The human brain is literally one of the most complex structures known in the Universe – which is itself the greatest of all complexity. Your brain has about 80 billion neurons – the cells that process input from the senses and send signals to your body through the nervous system. Neurons are also networked, communicating to each other through connections called axions and dendrites. There are on the order of 100 trillion connections between neurons forming the neural network that creates who you are.
NGC 6888 the “Crescent Nebula” has been said to resemble a giant brain in space
– Patrick Hsieh CC BY-SA 4.0
The Universe is networked as well. While we may think of space as objects separated by vast tracts of…well…space, that’s not entirely the case. The Universe we see with our scientific equipment is referred to as the “Observable Universe” approximately 90 BILLION light years in diameter and containing on the order of hundreds of billions to a few trillion galaxies. These galaxies, like our Milky Way, collections of billions of stars, are themselves grouped into galaxy clusters. Our Milky Way is part of the “Local Group” which contains the neighbouring Andromeda and Triangulum galaxies as well as 50 other galaxies. Those galaxies are in turn part of a larger group called the Virgo Supercluster. The space between groups and clusters is not empty but rather hosts connecting filaments of both ordinary and dark matter that stretch for millions of light years. In this way, the Universe can be thought of as a giant network of galaxy clusters all interconnected similarly to neural networks in the brain. That network is called the Cosmic Web.
A simulation of the formation of the Cosmic Web from the beginning of time to the present
A Universe Within a Universe
The research to find quantifiable similarities between both networks was born in a partnership between neuroscience and astrophysics. Using techniques and tools from both disciplines, Vazz and Feletti looked at these two networks to find quantifiable similarities beyond the perceived visual similarity. Were these networks comparable and, if so, what does that mean?
The researchers used 4 micrometer thick slices of the human cortex – the outer layer of the brain which is responsible for processing language, sensory information, thought, memory, and consciousness. These were compared to 25 megaparsec (1 parsec = approx. 3.26 light years) thick “slices” of Universe taken from a computer simulated volume of 1 million cubic megaparsecs of space. The slices of brain and Universe are relatively comparable in thickness then given that both are 27 orders of magnitude in size different from each other.
Cosmic Web and Brain Samples at 4x, 10x, and 40x Magnification
– Vazza F and Feletti A (2020)
Left: section of cerebellum, with magnification factor 40x, obtained with electron microscopy (Dr. E. Zunarelli, University Hospital of Modena); right: section of a cosmological simulation, with an extension of 300 million light-years on each side (Vazza et al. 2019 A&A).
Depending on the scale the slices were examined – the similarity in structure wasn’t always apparent. But at 40x magnification in the brain tissue, the researchers began to see similarities in structure. 40x magnification represents a scale of 0.01-1.6mm in the brain and 1-100 megaparsecs in the Universe.
Here, the neuronal network appears like the galaxy clusters. Furthermore, the similarity of the networks can be objectively measured and compared using two techniques. The first is “network degree centrality” which measures the lengths of the network connections and degree of connectivity in a given network. The nucleus or centre of a neuron is much smaller in radius than the length of connecting axions and dendrites. Similarly, galaxy clusters are much smaller in radius than the length of connecting filaments. The second method to objectively compare both networks is the “clustering coefficient” which quantifies the amount of structure adjacent to each connection node (neuron or galaxy cluster) and compares that structure to a random point within the network. This comparison contrasts organization vs randomness in both networks.
Vazza F and Feletti A (2020) Figure 3: “Top panels: zoomed details of the reconstructed connections between nodes for three example of networks in our sample (blue lines, superimposed to the density contrast maps). Bottom panels: distributions of clustering coefficient and of degree centrality for all slices”
Applying the techniques at these scales, Vazz and Feletti found “remarkable” similarities between both the brain and the Universe. They also found that the networks were more like each other than other biological and physical structures including tree branches, the dynamics of cloud formation, or water turbulence. These other structures are fractal in nature. Fractal patterns are self-repeating and look the same regardless of what scale you observe them.
By contrast, the Universe looks completely different at smaller than larger scales. Galaxies and solar systems don’t resemble the Cosmic Web that they create. So too the brain no longer resembles the neural network when observed at different scales. Scale itself might be important to the creation of these structures in terms of how they organize themselves.
The researchers conclude their findings “hint at the fact that similar network configurations can emerge from the interaction of entirely different physical processes, resulting in similar levels of complexity and self-organization, despite the dramatic disparity in spatial scales of these two systems.” In other words, networks like the brain and the Universe may share similar structure while being completely different in size and formed by different processes (gravity vs biology). Yet it’s possible something caused both to evolve and grow in a similar way.
This “Mandelbrot Zoom” is a fractal pattern that looks similar regardless at what scale it is observed unlike the Brain and Universe which appear very different at different scales
The researchers noted two other interesting similarities between the brain and the Cosmic Web. The first was ratios of composition. The brain is 77% water while similarly the Cosmic Web is approximately 73% dark energy. Water and dark energy are not a part of the network itself but are considered “passive material” or passive energy. The presence and ratio of passive material/energy might be of relevance to how these networks form.
A second fascinating similarity is that the amount of computer data required to map the simulated Universe models is comparable to the theoretical memory storage limits of the human brain. Between 1-10 Petabyes (1 Petabyte = 1000 Terrabytes) of data is needed to simulate the evolution of the observable
Universe at scales where the Cosmic Web becomes apparent. Estimates on the total storage capacity of the human brain is about 2.5 Petabytes.
A human could then theoretically store a good portion of the observable Universe’s structure…inside their brain. Or, even more astonishing to consider, the Cosmic Web could theoretically store the data of a lifetime of human experiences.
Hubble “eXtreme Deep Field” image shows some 5,500 of the
most distant galaxies ever imaged. – NASA/ESA
As well as similarities, there are differences between the Cosmic Web and the brain. While the samples of brain used were from the cortex, the whole brain is not uniform. Different parts of the brain are structured for different purposes while a key feature of the Universe is its uniformity in nearly all directions.
Links between neurons in the brain are for the transmission of sensory information while links in the Universe transmit energy and matter alone. Vazz and Feletti hope their research will inspire the development of more powerful algorithms to discover even more similarities between the brain and the Universe.
Perhaps we’ll learn about the conditions that cause two networks born out of completely different processes to resemble each other so closely.
We’ve heard Carl Sagan describe how our bodies are literally made of stars. Now we are beginning to understand that our brains may be patterned like them as well. A whole universe of connections is in your mind – a universe within a universe – and one capable of reaching out to the other that gave rise to it. Billions of neurons touching billions of stars – surely spiritual.
Edited by riseabovethought, 08 February 2022 - 12:57 PM.
