What is the ‘uncertain zone’ of the brain that intrigues scientists – 04/10/2023 – Equilibrium and Health

The human brain is an organ as powerful as it is mysterious.

In this mass of approximately 1.5 kg live about 86 billion neurons that make up the gray matter. That’s almost equal to the number of stars in the Milky Way.

These neurons connect to each other through synapses. It is estimated that the number of synapses in the human brain is close to a quadrillion, that is, 1 followed by 15 zeros.

Scientists know that these connections exist, but they still cannot discover exactly how and where all the information that arrives and leaves our brain is produced, stored and processed thanks to these synapses.

An example of these conundrums of the brain and memory is the so-called “doubtless zone”—a region about which there are more questions than answers.

The first to describe this part of the brain was the Swiss neuroanatomist Auguste-Henri Forel, in 1877.

“It is a region about which nothing can be said with certainty,” wrote Forel.

Today, almost 150 years later, the situation remains much the same. Despite all the advances in medicine and technology, no one really understands what the gray area is.

However, experts are aware that the zona incerta plays a role in key processes in the human body, such as memory.

Even so, it is still an understudied part of the body.

But recent studies have found new information about this important but neglected region of our brain.

few certainties

The zona incerta is a band of gray matter located in the central area of ​​the brain.

“It’s like a sheet of neurons that stretches between the thalamus and the hypothalamus,” Huizhong Tao, professor of physiology and neurosciences at the University of Southern California, told BBC News Mundo, the BBC’s Spanish-language service.

Along the uncertain zone, at least four subregions have been identified, each associated with a specific role, ranging from motor and visceral functions to arousal and attention.

The uncertain zone has also been linked to functions such as sleep, pain regulation and learning, explains Huizhong.

And a recent study in mice has shown that the zone may also play an important role in consolidating long-term memory.

But beyond that, little is known about the mechanisms under which this zone of the brain acts and how it communicates with other regions of the brain to carry out tasks.

For example, the zona incerta is one of the few regions commonly targeted for stimulation in Parkinson’s patients, but scientists aren’t sure why it has the ability to alleviate the disease’s symptoms.

Why is it difficult to study this zone?

The zona incerta is a thin structure located deep in the brain, so it’s difficult to study in living people, says Huizhong.

Furthermore, explains the specialist, the chemical and cellular composition of this membrane is complex.

Each of its subdivisions apparently has different functions, and its neurons involve the action of up to 20 different neurotransmitters, making it difficult to analyze them as a whole.

And, as if that weren’t enough, “its connection to other parts of the brain is extremely complex,” says Huizhong.

The zona incerta communicates with nearly every center of neural circuitry, from the cerebral cortex to the spinal cord, which also helps explain why it is involved in such diverse roles.

What was discovered?

A recent study in mice, conducted by the University of Freiburg and the Max Planck Institute for Brain Research in Germany, has found new evidence that the zona incerta may play a key role in attention and long-lasting memory.

The analysis showed that the zona incerta has a particular connection with the cerebral neocortex, the largest and most evolved region of the brain.

In humans, the neocortex is considered the largest repository of long-term memories. It is also responsible for several of the cognitive functions that distinguish us, such as reasoning, consciousness and language.

However, it is not known exactly how memories and experiences arrive and are stored there.

Internal and external signs

To form new memories, the brain must make a connection between sensory stimuli coming from outside and internal signals that contain information from past experiences.

To do this, neurons exchange signals that excite (turn on) or inhibit (turn off) certain areas of the brain as needed.

In the past, studies have focused on looking at the effect that arousal signals have on learning and memory.

This new study focused on inhibitory signals arising from the uncertain zone.

Scientists have observed that the zona incerta plays a role in learning and memory, not by exciting other neurons, but by inhibiting them.

This inhibition ends up creating an “inhibition network” that disables certain connections to optimize the flow of excitatory connections in other areas.

This “inhibitory network” could be compared to a system of traffic lights that coordinate with each other to stop traffic on some streets and thus allow it to flow more quickly on others.

“What we observed was a complete redistribution of inhibition within the system,” says Anna Schroeder, lead author of the study.

Through this mechanism, the net result is an excitation of neocortical circuitry to facilitate learning.

Why is it important?

“This study is very interesting,” says Huizhong, who was not involved in the research.

“It offers new insights into neural mechanisms for learning and memory.”

The authors of the research say that understanding the mechanisms by which memories are formed could be useful for treatments against memory loss, anxiety disorders or Parkinson’s.

They even mention that the zone could have implications for the development of artificial intelligence and software development.

For now, however, they are convinced that their study serves to “inspire other researchers” to continue looking for clues to solve the mystery of the zona incerta.

This text was published on BBC News Brazil.