The brain and the movement


Recently, a team of neuroscientists at the Champalimaud Foundation, discovered the mechanism that allows the brain to distinguish when the person is in motion from when it is stopped, from the one when it is stopped and what moves is what surrounds it. This discovery was revealed earlier this month.

When the human being turns his head to one side, his field of vision “turns” to the opposite side, when we travel on a car or in another means of transportation, the landscape passes on the other side of the window, however, we have the notion that It is us who are moving, not what surrounds us. How does the brain allow us to have this perception?

This question was the starting point for the research, led by Eugenia Chiappe, who had their findings published in the journal Nature Neuroscience.
Researchers had already discovered in the fruit fly’s brain a neural circuit that creates an internal representation of the direction and speed of the insect’s locomotion, allowing it to see where it is going at each moment.
They also believe that these results may be similar for other animals, including of course, humans.

Eugenia Chiappe, stated that “our perception of our movements is so natural to us, it is so deeply rooted in our subconscious that we underestimate the complexity and fragility of the biological mechanisms that support it”, but “when we lose, as happens in certain mental illnesses or following an injury, we lose the ability to interact with the world”.

To better understand this mechanism, the team studied a special type of neurons from the same insect that is already being studied, the fruit fly, the HS cells (horizontal system cells), located in the area of the visual brain of the fly called “plaque Lobular”, which are part of another monitoring system, which transmits to the fly’s brain that it was she who moved. This type of cells, known as “optical flow processing”, also exist in the primate brain, and in the case of these animals, neurons receive visual information regarding eye movements and the head, but also receive non-visual Their movements of locomotion and movement.

“Until now, this had not been proven”, said Eugenia Chiappe, “because it was very difficult to artificially create an illusion that it is walking.”
With the fruit fly, enough to do the test, it is enough to place it on top of a suspended ball in the air, which rotates when the fly walks, and at the same time, directly registers the activity of its HS cells.

To confirm the contribution of non-visual signals to insect HS cell activity, the scientists switched off the lights. “What we have now shown in the fruit fly is that even in the dark, HS cells continue to monitor body movements through non-visual signals”, said Eugenia Chiappe.
Thus, the researchers have also realized that these neurons integrate the visual and non-visual signals when they turn on the lights.

They understood that “when the fly sees, the two types of signals cooperate”, that is, thanks to this combination of signals, the HS cells can monitor and control the direction of the fly.
To confirm this visual and non-visual cooperation, a third experiment was carried out, in which the outside world “reacted” in a totally anti-natural way, that is, when the fly turned to one side, the visual field “rotated” exactly to the same side. In this case the HS cells became disoriented, “directional selectivity of HS cells decreased and HS cells became unable to differentiate the directions to tell the fly’s brain to which side the fly was turning”, explained Eugenia Chiappe.

In the course of this scientific study, the researchers also discovered that the fly’s ability to perceive how fast it was traveling and how far apart the objects are, so that it can correctly calculate the total distance to the place where it wants to land in control.
HS cell activity correlates with the velocity of the fly’s body, both when moving in a straight line and when it changes direction, and this means that “it is from HS cell activity that the fly’s brain calculates its Real physical speed, linear and angular”.