Brain development: the “infrastructure powerhouse” above our heads

Produced by: Science Popularization China

Author: Wang Fei (PhD in Neuroscience)

Producer: China Science Expo

Since 2000, September 16th of each year has been designated as "China Brain Health Day". With the improvement of human health awareness, brain health has gradually attracted everyone's attention. However, many of us do not actually understand this core organ, and we are also full of questions about the development and function of the brain.

Brain: Do you really know this organ in your body?

Why is there such a big difference in IQ between people? Does Einstein, who has the smartest brain, really have an extra brain compared to the average person?

Albert Einstein

(Photo source: Veer Gallery)

In fact, from an anatomical point of view, there is not much difference between people's brains. The operation of the brain is so finely regulated and multiple constraints that any relatively large difference would be fatal. The differences between each of us are more caused by the different speeds of brain development.

Some people's brains grow faster and they may be child prodigies from an early age; while some people's brains grow slower and they may always be slow in reaction.

But whether they are smart or stupid, their brain development is a long and complex process, more complex and sophisticated than any industrial process in today's human society.

In fact, our brain is also a "powerful infrastructure country". Its development speed can be said to be the fastest in the human body . Below I will talk about the four characteristics of brain development. After listening to these four characteristics, let's evaluate whether our brain can win the title of "powerful infrastructure country".

Long development: long overall time, many projects

First of all, the first characteristic of brain development is that it is long . Note that long does not mean slow, but it means that the overall time is long and there are many projects to be carried out.

Unlike other animals, the human brain needs to go through nearly a decade of development and learning before it can become an independent brain. Compared to the deer that can run as soon as they are born, or the birds that can sing as soon as they hatch, we humans are really too "late bloomers".

Fetal brain development

(Photo source: Veer Gallery)

We all know that the human brain is a multifunctional organ that not only collects information but also controls movement. It not only develops language but also requires training of thinking.

Just taking the process of learning a language as an example, we can feel the long process of brain development.

Babies start babbling at two months old, but this is just the beginning, when the brain begins to command the muscles to make sounds. In the next few years of learning, humans need to remember many nouns and know their pronunciations. But just "jumping words" is not enough. If a person wants to express his or her ideas accurately, he or she must accumulate a lot of experience and summarize a lot of experience. If you want to learn to write and communicate with others, decades of education from elementary school to middle school are not enough.

During this long and complex process of brain development, both genes and environment influence the formation of each unique brain at all times.

DNA three-dimensional structure model

(Photo source: Veer Gallery)

From pregnancy to birth, and then through more than a decade of development, the external environment experienced by each person is very different. The external stimulation received by the brain at each stage is also different, which leads to the differences in each of our brains.

Developmental scale: A huge project in a small brain

Secondly, the scale of brain development is huge. The reason why the development of the human brain is so long is that it is a huge project. This project is even more complicated than building an aircraft carrier or a manned moon landing.

Although this process is confined to our little brains, until now, no country has been able to simulate one percent of this project, which involves both cell differentiation and cell migration, the combination of different structures, and the control of complex information.

Simply put, brain development is like a traditional northern art - blowing sugar figures.

Blowing sugar figures

(Photo source: Veer Gallery)

The cell layer on the dorsal side of the embryonic upper surface develops into a pancake, called the neural plate . At 14 days after birth, the neural plate gradually folds into the neural tube . At 25 days, the neural tube looks like a blown-up candy man, with three bulging balls appearing, which later develop into the forebrain, midbrain, and hindbrain .

With these basic structures, the rest is refinement. A pair of small protrusions are pinched out of the bulge in the front, which later develop into eyes. The thin and long tube in the back gradually develops into the spinal cord. The brain and spinal cord constitute the central nervous system, while the peripheral nervous system is the nerve fibers sent by the brain and spinal cord to control the movement of limbs and internal organs. The brain sends hundreds of nerve fibers to the limbs, which establish connections with muscles and receptors.

Embryonic development

(Photo source: Veer Gallery)

Until the day the fetus is born, the brain is still changing. The brain growth reaches half of the adult's at six months, 60% at one year old, 75% at two and a half years old, 90% at six years old, and only at ten years old is it the same as an adult's .

From a fertilized egg cell to the 14 billion cells in an adult brain, this project is like asking all the people on Earth to build a new city on Mars. Not only does everyone have their own house, but there must also be transportation, material supplies, etc. In fact, the development of the brain is much more complicated than building a new city.

Dramatic growth: a leap from one to ten billion

Thirdly, another characteristic of cell development in the brain is that it is intense, or fast, because the main work of this huge project is completed in just a few hundred days .

No other organ in the human body develops as rapidly as the brain. In the ten months from fertilization to birth, the number of neurons increases from one to nearly ten billion .

And it's not just the number that changes. These neurons need to be connected to each other to build a complex information network. This network is even more complex than the current Internet. Just imagine that the neural network in the brain is like each of us holding hundreds of mobile phones in our hands to communicate with everyone on the earth. What a spectacular sight!

Neurons

(Photo source: Veer Gallery)

Let’s look at another set of data, which may be more intuitive.

More than 4,000 nerve cells appear in the fetus' brain every second, and 30,000 synaptic connections are formed every second within a square centimeter, a speed that cannot be achieved by any current Internet communication.

In fact, we can also see this from the growth of a baby, who goes from knowing nothing about the world to knowing everything like a "little adult" in just a few years. This is much faster than the robots today!

The input of information, the establishment of intelligence, the continuous updating of structure, and the establishment of various complex functions of the brain can all be described as "advancing by leaps and bounds."

Neural network in the human brain

(Photo source: Veer Gallery)

There is also a critical period for the development of the brain. During this period, the brain develops rapidly and learns anything faster. Once we miss this critical period, we will need several times more effort to learn the same thing and acquire the same function.

During the critical period, huge changes occurred in the brain, the dendritic spines of nerve cells were pruned, and the number changed from increasing to decreasing. The cells in the brain did not increase continuously, and some cells died actively during development, a process called programmed cell death .

Developmentally complex: strong plasticity that is constantly updated

Finally, let’s look at another characteristic of brain function development: complexity.

Don’t be amazed at how sophisticated a Swiss watch is, with thousands of parts packed into a tiny space. Don’t be shocked by the complex engines of sports cars, which are nothing more than a big rock compared to the complexity and precision of the brain.

It can be said that the human brain is the most complex machine in the world. Even the brain of a tiny fly may not be a match for our current giant computers.

We just said that there are about 14 billion nerve cells in a mature brain, and each nerve cell has hundreds of synapses, and these cells communicate with other cells through synapses.

To complete a simple action, it often requires the work of dozens of cells. Nerve cells can transmit information through electrical signals or chemical signals . Dozens of cells form a loop, called a neural circuit .

Connected neuronal circuits

(Image source: Science)

The neural circuits in the human brain are much more numerous than the circuits in a computer, and each circuit can change according to changes in the environment. In this way, our brain is like a road network in a city, crisscrossed and densely packed.

What is even more difficult for us to imagine is that the brain is changing from childhood to adulthood. This phenomenon of the brain changing due to changes in the external environment is called brain plasticity.

In other words, the brain is like plastic, being kneaded by the environment, constantly changing its structure and function to complete different tasks.

This is why the brain is more complex than any machine today, because once an artificial machine is created, it is difficult to change it and can only maintain its original function. However, our brain is constantly changing, its structure is also changing, and its function is thus updated.

Conclusion

By understanding brain development, we will marvel at its delicate process. A fully developed brain is like a fine piece of fired porcelain that does not allow us to make any changes.

It can also be said that the brain in each of our heads is an Internet, with countless information being exchanged between neurons every day, forming the most complex network structure in the world. Such a masterpiece cannot be compared with any man-made product, and the lengthy, huge, intense and complex process of its construction is enough to make it a "powerful country in infrastructure."