Anyone who has felt the need for several overflow brains just to keep up with a busy day will know the dread of a cartoon-like collapse. The good news, according to recent research, is that unsteadiness is the normal state of the human brain.

As science writer Carly Cassella puts it at ScienceAlert, “The human brain’s complexity verges on the brink of chaos, physicists say.” Our minds just never quite get used to it.

Poised Between Two Phases Without Collapsing

The physicists are Helen Ansell and István Kovács of the Physics and Astronomy Department at Weinberg College of Arts and Sciences at Northwestern University in Illinois. Examining the anatomy of neurons in the brains of humans, mice and fruit flies, they found that the cellular structure of the brain sits at a point that is poised between two phases:

When a magnet is heated up, it reaches a critical point where it loses magnetization. Called “criticality,” this point of high complexity is reached when a physical object is transitioning smoothly from one phase into the next…

Now, a new Northwestern University study has discovered that the brain’s structural features reside in the vicinity of a similar critical point — either at or close to a structural phase transition.

NORTHWESTERN UNIVERSITY. “BRAIN’S STRUCTURE HANGS IN ‘A DELICATE BALANCE,’” SCIENCEDAILY, 10 JUNE 2024. THE PAPER IS OPEN ACCESS.

The researchers don’t know whether this state is universal in brains as only three types have been studied so far.

Like Ice Becoming Water…

No one has yet named the phases that the brains’ structures seem to hover between:

“The structure of the brain at the cellular level appears to be near a phase transition,” said Northwestern’s Helen Ansell, the paper’s first author. “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. 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.”

NORTHWESTERN. ““A DELICATE BALANCE”

So how do the researchers know that these brains are near a phase transition?

Brain cells are arranged in a fractal-like statistical pattern at different scales. When zoomed in, the fractal shapes are “self-similar,” meaning that smaller parts of the sample resemble the whole sample. The sizes of various neuron segments observed also are diverse, which provides another clue. According to Kovács, self-similarity, long-range correlations and broad size distributions are all signatures of a critical state, where features are neither too organized nor too random. These observations lead to a set of critical exponents that characterize these structural features.

NORTHWESTERN. ““A DELICATE BALANCE”

Cassella offers,

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.

CARLY CASSELLA, SCIENCEALERT

Cassella’s comparison to the cell membrane is apt. Perhaps it will turn out that a slush environment is essential for a structure as complex as a brain. Forced into one phase only, it might start to malfunction.

The Human Brain Is a Lot Like the Universe

If we find these outcomes odd, it’s helpful to keep in mind that the human brain, for example, also has many similarities to the universe itself. Among others,

Your brain is made up of a complex network of nearly 100 billion neurons that form 100 trillion neural connections. Neurons are clustered into a hierarchical network of nodes, filaments, and interconnected neural clusters that shape the complex thoughts, feelings, and emotions you experience. But these neurons make up less than 25 percent the mass of your brain, leaving the remaining 75 percent as water.

In a bizarre coincidence, the observable universe also contains an estimated 100 billion galaxies. The teetering balance between the pull of gravity and the accelerated expansion of the universe forms a cosmic web of string-like filaments composed of ordinary and dark matter.

TIM CHILDERS, “THE HUMAN BRAIN LOOKS SUSPICIOUSLY LIKE THE UNIVERSE, WHICH MAY FREAK YOU OUT,” POPULAR MECHANICS, NOVEMBER 17, 2020

Seen from that perspective, the brain’s delicate hover between two phases is just one of many remarkable facts about it.

Cross-posted at Mind Matters News.