Science Alert reports:

The human brain is said to be the most complex object in the known Universe. Its 89 billion neurons each have around 7,000 connections on average, and the physical structure of all those entities may be balanced precariously on a knife’s edge, according to a new study.

Two physicists at Northwestern University in the US – Helen Ansell and István Kovács – have now used statistical physics to explain the complexity seen in a highly detailed 3D map of not just part of a human brain, but part of a mouse’s and fruit fly’s brains as well.

At a cellular level, their framework suggests the high-level hardware encased in our skulls is at a structural sweet spot closely approaching a phase transition.

“An everyday example of this is when ice melts into water. It’s still water molecules, but they are undergoing a transition from solid to liquid,” explains Ansell.

“We certainly are not saying that the brain is near melting. In fact, we don’t have a way of knowing what two phases the brain could be transitioning between. Because if it were on either side of the critical point, it wouldn’t be a brain.”

In the past, some scientists have suspected that phase transitions play an important role in biological systems. The membrane that surrounds cells is a good example. This lipid bilayer fluctuates between gel and liquid states to let proteins and liquid in and out.

By contrast, however, the central nervous system may teeter on a critical point of transition, while never actually becoming something else. [Continue reading…]