The human brain It is said The most complex object in the known universe. the 89 billion neurons New research suggests that on average, each has around 7,000 connections, and the physical structure of all these entities could be in a dangerously dangerous balance.
Two physicists, Helen Ansell and Istvan Kovács, from Northwestern University in the US, have used statistical physics to explain the complexity found in highly detailed 3D maps of parts of the human brain, as well as parts of mice and fruit flies.
At the cellular level, their framework suggests that the higher-level hardware housed in our skulls is in a structural sweet spot, approaching a phase transition.
“An everyday example is when ice melts and turns into water. It’s still water molecules, but a change from solid to liquid has occurred.” explain Ansel.
“We’re not saying the brain is melting. In fact, there’s no way to know what transition between the two stages the brain is in, because if the brain is on either side of the tipping point, it’s not a brain.”
In the past, some scientists Phase transition They play important roles in biological systems, such as the membrane that surrounds cells, where the lipid bilayer can fluctuate between a gel and liquid state, allowing proteins and fluids to enter and leave.
In contrast, the central nervous system may never actually become something else, but may vacillate at key points of transition.
A common feature of these critical points is their neuronal branch-like structure, Fractal PatternsFractals, such as those found in snowflakes, moleculeor the distribution of galaxies, is System ComplexIn physics, The fractal dimension is Edge of ChaosBetween order and disorder.
Ansell and Kovac now argue that the nanoscale presence of fractals in 3D brain reconstructions is a sign of this “criticality.”
Data limitations allowed the pair to analyze only a single subregion of the human, mouse, and fruit fly brains, but even with these limited images, the team found fractal-like patterns that looked similar whether they were zoomed in or out.
The relative sizes and diversity of different neuronal segments appear to be maintained across scales and species: the brain system is neither too organized nor too random, striking a sweet spot between the costs of neural “wiring” and the requirements for long-distance connections.
This “Goldilocks effect” is likely a universal principle across all animal brains, Ansell and Kovács argue, but more research will be needed to prove it.
“At first, these structures look quite different. The entire fly brain is about the same size as a tiny human neuron.” To tell “But then we discovered new properties that were strikingly similar,” Ansell said.
Further research is needed to determine whether this shared importance exists across animal brains and among different species.
In previous studies, Neuronal DynamicsHowever, until recently it was not possible to analyse and compare animal brain structure at the cellular level.
Of course, data limitations still exist, but there is currently a large-scale effort underway in neuroscience to map the brain’s anatomy and connections. As detailed as possible.
a 1 cubic millimeter The structure of the human brain was recently reconstructed, and last year We are the first A complete map of the Drosophila brain Cellular map of the mouse brain.
“[The structural level] It was a missing piece in thinking about the complexity of the brain.” To tell Istvan Kovács, a physicist at Northwestern University.
“Unlike a computer, where any software can run on the same hardware, in the brain the dynamics and the hardware are intimately linked.”
Ansel To tell The team’s findings “pave the way” for simple physical models that can explain statistical patterns in the brain, which in future could be used to improve brain research and train artificial intelligence systems.
This study Communication Physics.