What is a connectome? The new maps of the brain

The human brain is one of the most complex natural systems known. This is not simply because technological developments have allowed the creation of measurement tools relatively recently. adequate to study this set of organs, not to the fact that an average human brain of an adult person contains approximately 80,000,000 neurons. The key is how these nerve cells are connected.

As we will see in this article, the concept of connectome was born to help us understand the internal logic of something as complicated as a brain.

• Related article: "Parts of the human brain (and functions)"

What is the connectome?

As we have seen, there is an overwhelming number of nerve cells in the human brain. But also, each neuron is capable of connecting with hundreds, thousands of other neurons. These connections can change and develop over time.

It can be said that if our nervous system works it is because the neurons are capable of sending millions of nerve impulses to each other through these touchdowns, called synapse. Each neuron, individually, is not capable of performing any of the functions that allow us to think, feel, or even stay alive.

A connectome, then, is a mapping of the neural connections that exist in a nervous system or part of a nervous system, usually a brain. In recent years, several projects have appeared through which an attempt is made to understand the functioning of various parts of the nervous system thanks to these representations.

Structural connections and functional connections

When designing connectomes, it is possible to describe both structural and functional connections. The first ones reveal general and macroanatomical patterns of connectivity, normally embodied in beams of axons grouped that go from one part of the nervous system to another region of it. The second sample focuses on lower-dimensional details related to the probability that a group of connections neurons send certain nerve impulses to another group, a connection that is usually made in a more unpredictable and interrupted.

The Human Connectome Project

The concept of connectome is frequently compared with that of the genome, a word that in turn refers to the information contained in another type of biological structure: DNA. In the same way that in the 20th century biology and related scientific disciplines saw great hope in the possibility of unraveling the internal logic of the human genome, in recent years neuroscience and psychology, as well as computer science, have begun to look at the possibility of understanding the typical connectome of members of our species.

That is why in 2009 the Human Connectome Project, or Human Connectome Project, was born, financed by members of the National Institutes of Health, of the United States of America. The link of this initiative with health is evident: it is possible to map the connections of a healthy human brain, but also of one associated with a certain mental illness, in order to locate significant differences in the way in which the nerve cells communicate with each other in each case.

It is reasonable to look for the causes of certain disorders in this pattern of connectivity, since there is currently an important consensus around the idea that mental processes are more likely to have functional problems if groups of neurons that drive them are very separated from each other, since working with these distances involves assuming a higher cost metabolic. If in a brain that distance between groups of neurons is abnormally large, alterations in perception or behavior could appear. To this day the Human Connectome Project is still running.

A photograph of the brain?

As we have seen, the connectome is a kind of map of the brain, and its existence can facilitate the understanding of its operation. However, by its very nature, it is a tool with limited power.

This is so because the nervous system, especially the brain, is a constantly changing system. This is a phenomenon known as Neuronal plasticity, whereby any experience, regardless of its importance in psychological terms, causes the connectivity and activity patterns of our neurons to change.

Thus, a connectome can give an approximate idea of ​​the operation of certain behavioral logics, of the effects of some mental illnesses and brain injuries, and can even be used to create neural network learning systems in computers. In fact, there have already been promising achievements, such as recreating the connectome of the brain of a type of worm, create a simulation with him, and make him learn certain behaviors just as one of these animals would do without programming a line of code.

But a connectome cannot be used to accurately predict the behavior of an organism. with a brain like the human or one of similar complexity, since it is changing constantly. If we are able to reach that degree of knowledge, it seems that there is still a long way to go.