Mapping the structure of the brain doesn’t fully explain its function

If we can fully map the structure of our brain, will we be able to understand how they work? This is the objective of researchers who try to build a wiring scheme, or Connectome, of our neuronal tracks – but now it seems that discovering the secrets of the brain is not so simple.

You can consider Connectome as a card of all possible roads along which neural signals can travel, but now Sophie Dvali At Princeton University and his colleagues discovered that some of these roads were underused.

The researchers examined the connection of the nematode worm Caenorhabditis ElegansAnd compared it to a registration of the neural signals of the Ver, which they assembled by stimulating each neuron and following the way in which the signal he issued crossed the connection. This is possible in the worm because his brain only has 300 neurons in all his nervous system.

By dealing with the two data sets as mathematical networks, the team could determine if groups of neurons which are very densely interconnected in the Connectome also tend to exchange a large number of signals. They found that this is not always the case.

Dvali says that there have been a few examples of overlap for a high connection density and an exchange of signals, as for the groups of neurons responsible for the way the worm eats, where the two networks corresponded very well, or the neurons involved in the way in which it retreats, which is an important maneuver for a green danger. In the latter case, neurons were very connected in the two networks, but not identically. But, more generally, there was enough divergences for the team to say that the connection of an organism is not enough to predict all its behavior.

Andrew Leifer, a member of the team, also at Princeton University, says that the difference can be due to the fact that the signals between neurons do not always take the shortest path, and there are also known cases where neurons can communicate in a way beyond the “sons” that connect them. “We are used to using Connectome to guide our research, and often it is very useful and informative, but in many cases, there are so many links that we wanted to have more information,” he said.

“Connectomics data is often criticized as” Oh, you only get a structure. You don’t get behavior. ” And this document really proves this question to what extent we can [connect the two]”Explains Albert-László Barabási at Northeastern University in Massachusetts.

Then, the researchers wish to extend their study to take into account how the signals propagate in connection when several neurons are stimulated simultaneously and to look at more complex animals such as a larva of fruit flies, which has the largest connection of the entire brain described to date. “We are under a revolution at the moment of mapping the brain,” explains Barabási.