The brain makes its own maps
The brain of the rat and probably our brain too has a kind of "biological GPS" which provides individuals with a sense of spatial orientation, the ability to find their way when they need to go from one point to another, and to memorize spatial environments. The various types of neurons that contribute to achieving this are situated in two parts of the brain: the hippocampus and the entorhinal cortex.
The entorhinal cortex where information is processed prior to being sent to the hippocampus is where Edvard and May-Britt Moser discovered, in 2005, the existence of special neurons which they called "grid cells". These cells fire selectively when the individual passes different locations in the environment. The firing locations of each cell define a periodic triangular array that tiles the entire space visited by the subject, much like the cross points of graphics paper, but with an equilateral triangle as the unit of the grid. The brain thus makes its own maps.
The entorhinal cortex thus turns out to be a crossroads in the network of neurons that allows us to find our way. After discovering the "grid cells", the Norwegian neurobiologists identified other types of neurons which play a part in navigation. They indeed found cells, in the same brain system, that respond selectively depending on the direction taken by the animal, and others which tell it when it is approaching the physical limits of its environment. They also showed that the signals emanating from these different cells are used by spatial memory circuits situated in the hippocampus.
Edvard and May-Britt Moser's discoveries in particular the "grid cells" which the magazine Science described as the most important finding in the field for two decades are quite remarkable. They have shown how the brain calculates the
|Contact: Prof. Bernard C. Rossier|
European Molecular Biology Organization