What is a Connectome? The New Brain Maps

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

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

What is the connectome?

As we have seen, in the human brain there is an overwhelming number of nerve cells. But, in addition, each neuron is able to connect 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 contact sockets, called synapses. 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 in part of a nervous system, usually a brain. In recent years several projects have appeared through which attempts to understand the functioning of various parts of the nervous system thanks to these representations.

Structural and functional connections

When designing conectomas, it is possible to describe both structural connections and functional connections. The first reveal general and macroanatomic patterns of connectivity, usually embodied in bundles of grouped axons that go from one part of the nervous system to another region of the latter. The second show focuses on details of smaller dimensions related to the probability that a group of neuronal connections send certain nerve impulses to another group, a connection that is usually made in a more unpredictable and interrupted manner.

The Human Connectome Project

It is common to compare the concept of connectome with that of the genome, which in turn refers to the information contained in another type of biological structure: DNA. In the same way that in the twentieth 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 the members of our species.

That is why in 2009 the Human Connectome Project was born, or Human Connectome Project, 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 one associated with a specific mental illness, in order to locate significant differences in the way in which the cells Nervous 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 functionality problems if the groups of neurons that drive them are very far apart. Yes, since working with these distances involves assuming a higher metabolic cost. If in a brain that distance between groups of neurons is abnormally large, alterations of perception or behavior could appear. To this day, the Human Connectome Project is still underway.

A photograph of the brain?

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

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

Thus, a connectome can give an approximate idea of the functioning of certain behavioral logics, the effects of some mental illnesses and brain injuries, and can even serve to create learning systems by neural network in computers. In fact, promising achievements have already been made, such as recreating the brain’s connectome of a worm type, creating a simulation with it, and making it learn certain behaviors just as one of these animals would without programming a line of code .

But a conectoma can not be used to accurately predict the behavior of an organism with a brain like the human or one of similar complexity, since it is constantly changing. If we are able to reach that level of knowledge, it seems that there is still much to be done.