The information below refers to the time of the award.
Edvard Moser was born 1962 in Ålesund and May-Britt Moser in 1963 in Fosnavåg, Norway. Both studied several different disciplines, in particular mathematics, statistics, computer programming, neurobiology and psychology at the University of Oslo, where they received doctorates in neurosciences in 1995, followed by post-doctoral training in the United Kingdom. On their return to Norway in 1996, they were nominated as associate professors in biological psychology at the Norwegian University of Science and Technology (NTNU) in Trondheim. They are now professors of neurosciences at the Faculty of Medicine of this university. At this same university, they founded in 2002 the Centre for the Biology of Memory, and in 2007 the Kavli Institute for Systems Neuroscience, where they hold the positions of Director and Co-director respectively.
Edvard and May-Britt Moser are both fellows of the Norwegian Academies of Sciences and Technological Sciences, as well as of various other scientific bodies. They have received several distinctions, in particular the W. Alden Spencer Award of Columbia University in 2005, the Liliane Bettencourt Prize for Life Sciences in 2006, and the Eric K. Fernström’s Great Nordic Prize in 2008.
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 position of the organism in its spatial environment, completely overturning prior conventional thinking in the field.
How does the brain of living organisms, particularly mammals, enable individuals to establish their spatial location, to find their way from one point to another and to store this spatial information in their memory? For more than ten years May-Britt and Edvard Moser have focused their research on this question, and in so doing have made some remarkable discoveries.
Back in the early 70’s, John O’Keefe and John Dostrovsky at the University College of London had already made a start. They observed that when a rat was moving around unhindered, some of the cells in its hippocampus (a small structure situated in the medial temporal lobe of the brain) suddenly fired when the rodent was in certain places within its environment. They also noticed that this neural activation was dependent neither on the orientation nor the trajectory of the animal, but only on where exactly it was located. These neurons were therefore called “place cells”.
In 1985, Jim Ranck’s research group at the University of New York revealed another group of neurons, named “head-direction cells” with a complementary role to that of place cells. Head-direction cells activate only when the rat’s head is turned in a specific direction, regardless of the spatial location of the animal.
May-Britt and Edvard Moser’s research work has shed new light on how space is computed in the brain. The Norwegian researchers have shown that a different part of the brain located beside the hippocampus – the medial entorhinal cortex – plays an important part in spatial awareness. This cerebral structure (which pre-processes information before sending it to the hippocampus) holds a two-dimensional topographic map enabling the animal to find its way from one point to another.
In 2005, the two neurobiologists and their team discovered that one of the key elements of this map consisted of special neurons that provide information to the animal on distance covered and the direction. They called them “grid cells”. The name could hardly be more appropriate. These cells fire selectively at regularly spaced locations in the environment. Each of them is only activated when the animal is at places which, when linked to each other, make up a pattern of equilateral triangles tiling the entire environment within which the animal is moving. These triangular shapes positioned side by side make up a true grid.
These grid cells are arranged geometrically at regular intervals. Neighbouring cells have similar grid spacing and orientation, and the spacing of the grid increases progressively from the upper to the lower part of the entorhinal cortex.
Having been observed first in rats, then in mice and bats, these grid cells probably exist in all mammals including humans, even though the evidence for human grid cells remains indirect. Be that as it may, in 2007 Science magazine qualified their discovery as one of the most important in the field for more than two decades.
Later, in 2008, May-Britt and Edvard Moser added “border cells” to this list of neurons involved in spatial representation. These cells, which are also located in the entorhinal cortex, are intermingled with the grid cells and head-direction cells and respond when the animal reaches the borders of its cage.
The grid cells, head-direction cells and border cells make up a network of neurons each of which plays a distinctive part in an animal’s representation of its spatial location when moving. The mammalian entorhinal cortex map has innate components; this is demonstrated by the presence of rudiments of all these cell types when rats explore the outside world for the first time in their life.
But the functionality of these spatial neurons does not stop there. As the Norwegian researchers have demonstrated, the electrical signals generated by these cells in the entorhinal cortex are sent to the hippocampus to be used in spatial memory networks. They have shown how episodic memories in this structure, generated from entorhinal cortex spatial inputs, are separated from each other in memory storage so as to avoid subsequent interference between memories. They furthermore revealed how memory and external spatial information are handled in parallel in hippocampal memory networks and how brain rhythms contribute to differential routing of these different types of information.
These contributions attracted attention in the neurobiologist community, especially the new discoveries about grid cells. The crystal-like structure underlying their firing fields is indeed unique: it does not arise from its components, as it does in sensory systems, but instead is created by the brain itself.
The discovery of grid cells and their control of population codes in the hippocampus have led to a revision of established views of how the brain calculates the current position and spatial map of an organism. Thanks to May-Britt and Edvard Moser, spatial representation may have become the first psychological function to be described on a mechanistic level in the mammalian cortex.
Fig. Grid cells in the brain’s spatial mapping system
The figure shows the trajectory of a rat when running (black) with spike locations superimposed (blue). Each blue dot corresponds to an action-potential signal from the cell. The rat is running in a 1.5 m wide box.
Norwegian University of Science and Technology (NTNU)
Kavli Institute for Systems Neuroscience
Centre for the Biology of Memory (CBM)
Professor Edvard Moser, Director
Professor May-Britt Moser, Co-Director
Medical-Technical Research Centre
7491 Trondheim, Norway
Tel. : +47 73 59 82 78 (Edvard Moser)
Tel. : +47 73 59 82 77 (May-Britt Moser)