The human brain is one of the most complex natural systems known. This is not simply because technological development has only recently allowed the creation of adequate measurement tools to study this set of organs, nor because the 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 It was born to help us understand the internal logic of something as complicated as a brain.
As we have seen, there are 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 neurons are capable of sending millions of nervous impulses to each other through these contacts, 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 part of a nervous system, usually a brain. In recent years, several projects have appeared through which attempts are 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 connections and functional connections. The first ones reveal General and macroanatomical patterns of connectivity, normally embodied in bundles of grouped axons that go from one part of the nervous system to another region of it. The second samples focus on smaller details related to the probability that a group of neuronal connections sends certain nervous impulses to another group, a connection that is usually carried out in a more unpredictable and interrupted manner.
The concept of connectome is often compared to 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 set their sights on the possibility of understanding the typical connectome of members of our species.
That is why in 2009 the Human Connectome Project was born, funded 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 specific mental illness in order to locate significant differences in the way in which nerve cells communicate with each other in each case.
It is reasonable to look for the causes of certain disorders in this connectivity pattern, 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 separated. Yes, since working with these distances involves assuming a greater metabolic cost. If in a brain this distance between groups of neurons is abnormally large, alterations in perception or behavior could appear. Today the Human Connectome Project is still underway.
As we have seen, the connectome is a kind of map of the brain, and its existence can facilitate understanding of its operation 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. This is a phenomenon known as neuronal plasticity, by which 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 functioning 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 have him learn certain behaviors just as one of these animals would do without programming a single 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, given that it is constantly changing. If we are able to reach that level of knowledge, it seems that there is still a long way to go.
