Xxi: el segle de la neurociència
Misc 13/12/2020

Understanding the brain, a challenge as old as it is new

The study of the brain requires state-of-the-art technology and collaboration between disciplines

Cristina Pujades
3 min
Entendre el cervell,  un repte tan vell com nou

Scientist and professor at the Universitat Pompeu FabraThe fascination with the brain, that great unknown, has lasted for centuries. The human brain is a product of millions of years of evolution. We know that its capabilities do not simply depend on its absolute or relative size, but on the diversity of cells and patterns of connectivity between them. The brain is a mosaic of different types of cells, each with unique properties, the most common being neurons and glia cells. The adult human brain contains approximately one hundred billion neurons and more glia cells. Each neuron is connected to about one thousand other neurons, and this makes the number of connections approximately one hundred trillion. And these connections are organized into neural networks with specific functions. Given this data, it is not surprising that there are so many of us who want to understand how this complexity is generated.

We know that the functional neural circuits of the brain, and therefore the neural wiring networks, are built during embryonic development from established gene programs. These programs are developed in an exquisitely orchestrated way and allow us to implement the strategy of embryonic development: to build very simple neuronal structures where complexity will be added as the embryo develops. It is the same strategy that is followed when a building is constructed: first the foundations are made, and on top of that everything else is built.

If we can understand how the brain's stem cells execute these programs and how they coordinate to give rise to a functional brain during embryonic development, we will better understand the basic principles of neuron production in order to be able to reconstruct these neuron circuits for therapeutic purposes. This approach, however, only allows us to understand what the pieces of this meccano are and the instructions to follow in order to build it.

Following the same reasoning of understanding how complexity is added to simpler systems, and considering that evolutionary pressure causes species to maintain the fundamental functions for survival, revealing how the neuronal architecture of the brain is established in simpler organisms such as the Drosophila fly, the elegant worm, the zebrafish or the mouse, will help us to decipher the operating mechanisms in complex organisms such as humans. Surprisingly, the basic neural circuits are well preserved in all vertebrates - key gene mechanisms are even preserved in invertebrates!

A collective challenge

Technological revolutions accompany new discoveries, and in the last decade great strides are being made in mapping neural connections in the Drosophila brain and in vertebrates such as zebrafish and mice. The search is becoming more and more interdisciplinary. Biologists, physicists, computer scientists and mathematicians are working together to build the maps of neural connections in the various models.

Large-scale research initiatives, such as the European Human Brain Project, launched in 2013, or the American The BRAIN Initiative, launched by Obama in 2014, have committed to building collaborative research infrastructures in medicine, computing and neurosciences, with the aim of revolutionizing our understanding of how the human brain works. These initiatives incorporate experts in computer science and artificial intelligence (AI) to help decipher and model neural circuits as if they were connecting networks. The idea is to generate models that help understand the sophistication of our brain and its ability to generate complex behaviors. Despite criticism, great advances have been made and funding has been stimulated in Silicon Valley with the aim of developing new AI tools to crack the neural code.

What challenges will be faced in the next ten years? According to the MIT Technological Review, the first would be to understand what makes our brain unique, understanding what are the principles of this unique design that govern this variability. The second, to understand how the brain is able to solve complex computational problems in our daily lives (how we recognize different emotional states, how we translate languages, etc.) and third, how we use all this information to diagnose and prevent mental illness and how we restore brain functions when there is damage.

In order to successfully respond to these challenges we must join efforts and knowledge, continue working on interdisciplinarity and at the same time improve the technology available. This entails a global approach, so a technological infrastructure for worldwide collaboration is being considered. Will we all be able to agree, the scientific community, citizens and governments, to build it? Here we have another challenge that we should not take too long to solve.