May-Britt Moser

Introduction

May-Britt Moser (born 4 January 1963) is a Norwegian psychologist and neuroscientist who, with her then-husband Edvard Moser, identified grid cells in the medial entorhinal cortex, the neurons that give the brain a metric for space. The discovery, published in Nature in 2005, supplied the missing piece in a picture that had begun with John O'Keefe's place cells three decades earlier, and it earned the three of them the 2014 Nobel Prize in Physiology or Medicine. Moser has spent her career at the Norwegian University of Science and Technology in Trondheim, where she co-founded and helped direct two flagship research centres and trained a generation of systems neuroscientists.

Early Life and Education

Moser was born in Fosnavåg, a small fishing town on the west coast of Norway, the youngest of five children. She has described a childhood spent largely outdoors, watching and handling animals, and her strongest school subjects were mathematics and physics. She entered the University of Oslo in 1984 intending to study psychology, and it was there that she met Edvard Moser, whom she married in 1985.

As undergraduates the couple worked in the laboratory of the behavioural neuroscientist Terje Sagvolden on a rodent model of attention deficit disorder, an experience that produced their first published papers and gave them a grounding in behavioural analysis and experimental design. They were drawn, however, to the neural mechanisms beneath behaviour, and were inspired by the work of David Hubel and Torsten Wiesel on the visual system. They approached Per Andersen, a leading hippocampal neurophysiologist at Oslo, and persuaded him to take them on. Both completed master's theses on spatial learning in the dorsal and ventral hippocampus, and both received their doctorates in neurophysiology from the University of Oslo in 1995, May-Britt's under Andersen's supervision, with a dissertation on the structural correlates of spatial learning in the rat hippocampus.

Academic and Professional Career

During their doctoral years the Mosers made repeated research visits to the University of Edinburgh to work with Richard Morris, whose water maze had become the standard test of spatial memory, and May-Britt spent a period as a visiting postdoctoral fellow in O'Keefe's laboratory at University College London, where she learned single-cell recording techniques. A common misreading of her record places her doctorate at Edinburgh; her PhD was awarded at Oslo, and the Edinburgh and London appointments were postdoctoral visits.

In 1996, less than a year after defending their theses, the couple were appointed associate professors at the Norwegian University of Science and Technology in Trondheim, where they built a laboratory from scratch. May-Britt was promoted to full professor of neuroscience in 2000. A grant from the Research Council of Norway gave their group centre-of-excellence status in 2002 and a decade of funding, and in the same year they founded the Centre for the Biology of Memory. The centre became the Kavli Institute for Systems Neuroscience in 2007, with Edvard Moser as director and May-Britt as co-director; from 2013 to 2022 she also directed the NTNU Centre for Neural Computation. The two divorced in 2016 but continued to run the institute and publish together, an arrangement that has itself become a subject of comment in profiles of the pair.

Major Contributions to Psychology

The Discovery of Grid Cells

O'Keefe had shown that hippocampal place cells fire when an animal occupies a particular location. The Mosers asked where those spatial signals came from, and noted that almost every earlier recording study of the entorhinal cortex, the main gateway into the hippocampus, had placed electrodes near its ventral end. Recording instead from the dorsal medial entorhinal cortex, they found cells with multiple sharply defined firing fields. When the animals foraged in a large enough enclosure, those fields resolved into a strikingly regular triangular lattice that tiled the whole arena. The group named the cells "grid cells" for the simplest reason: the firing pattern looked like a grid. The finding was reported in Nature in 2005 by Torkel Hafting, Marianne Fyhn, Sturla Molden and the two Mosers.

A Coordinate System for Space

Grid cells fire at multiple locations arranged in a hexagonal lattice, and cells at the same dorsal-to-ventral level share both grid spacing and orientation while differing in phase, so that the population as a whole covers every point in an environment. The pattern held in darkness and with landmarks rearranged, which led the Mosers to argue that the grid is generated internally, by path integration, rather than copied from sensory input. In a conceptual paper they proposed that the pattern arises from continuous attractor dynamics in a recurrent network, and later work from their group confirmed a prediction of that model by showing that grid cells are organised into discrete modules with different grid scales.

Extending the Map

The Mosers' laboratory went on to identify additional functional cell types in the same circuit: border cells, which fire along the geometric boundaries of an environment and were reported in 2008; speed cells, whose firing tracks running speed, described in 2015; and object-vector cells, which encode the direction and distance to discrete objects, reported in 2019. Together with head-direction cells, these populations project onto the hippocampal place cells to form what is now generally described as the brain's positioning system. Because the entorhinal cortex is among the first regions damaged in Alzheimer's disease, and because disorientation is among its earliest symptoms, the work also opened a route from basic spatial cognition to clinical research.

Grid cells as a scanning beam

Twenty years after the discovery, the group reported that grid cells do considerably more than mark where the animal currently is. Using Neuropixels 2.0 probes, which record from thousands of cells at millisecond resolution, Abraham Vollan, Richard Gardner and the two Mosers showed in Nature in 2025 that roughly ten times a second the population sends a wave of activity outward from the animal's position and across the surrounding map, alternating about 30 degrees to the right and then to the left. Each sweep lasts about 125 milliseconds and corresponds to one theta cycle.

The decisive manipulation was deliberately low-tech. Food was tied to a fishing line and dragged unpredictably across the arena while the rat chased it, so that at every moment the experimenters knew where the animal's attention was. The sweeps then stopped behaving like a metronome: they narrowed from a wide cone anchored to head direction into a narrow beam aimed at the prey, quickened, and swung toward the target before the animal turned its head to follow. Subtracting the sweep component from the cells' positional firing leaves smaller and sharper grid fields, which implies that part of what had been measured for two decades as a broad firing field was this scanning activity all along. Edvard Moser has compared the pattern to the alternating calls bats use for echolocation.

Major Publications

Fyhn, M., Molden, S., Witter, M. P., Moser, E. I. & Moser, M.-B., "Spatial Representation in the Entorhinal Cortex," Science (2004)
Hafting, T., Fyhn, M., Molden, S., Moser, M.-B. & Moser, E. I., "Microstructure of a Spatial Map in the Entorhinal Cortex," Nature (2005)
Sargolini, F., Fyhn, M., Hafting, T., McNaughton, B. L., Witter, M. P., Moser, E. I. & Moser, M.-B., "Conjunctive Representation of Position, Direction, and Velocity in Entorhinal Cortex," Science (2006)
Moser, E. I. & Moser, M.-B., "Grid Cells," Scholarpedia (2007)
Solstad, T., Boccara, C. N., Kropff, E., Moser, M.-B. & Moser, E. I., "Representation of Geometric Borders in the Entorhinal Cortex," Science (2008)
Stensola, H., Stensola, T., Solstad, T., Frøland, K., Moser, M.-B. & Moser, E. I., "The Entorhinal Grid Map Is Discretized," Nature (2012)
Kropff, E., Carmichael, J. E., Moser, M.-B. & Moser, E. I., "Speed Cells in the Medial Entorhinal Cortex," Nature (2015)
Vollan, A. Z., Gardner, R. J., Moser, M.-B. & Moser, E. I., "Left–right-alternating theta sweeps in entorhinal–hippocampal maps of space," Nature 639, 995–1005 (2025)
Kanter, B. R., Lykken, C. M., Polti, I., Moser, M.-B. & Moser, E. I., "Event structure sculpts neural population dynamics in the lateral entorhinal cortex," Science 388, eadr0927 (2025)

Impact and Legacy

The Nobel citation, "for their discoveries of cells that constitute a positioning system in the brain," recognises one of the clearest mechanistic accounts of a cognitive function produced in modern neuroscience. The work has reshaped research on memory, sleep replay and spatial cognition, and it is a standard exhibit in arguments that abstract cognitive capacities can be explained by identifiable circuit computations. Moser's own institutional contribution is nearly as consequential: the Trondheim group she co-founded is now one of the most productive systems-neuroscience centres in Europe, its researchers trained in a laboratory culture she has consistently described as "excellent science through happy people and happy animals."

The science itself has been revised in important ways. Two studies published in Nature in 2015 by Krupic and colleagues and by Stensola and colleagues showed that grids are neither perfectly hexagonal nor environment-independent in the way the original account implied: grid orientation is influenced by the walls of the enclosure, and the lattice is measurably sheared by local geometry, which weakens the strong version of the claim that grid cells supply a universal metric. A separate line of work using Egyptian fruit bats, recorded by Yartsev, Witter and Ulanovsky, found a grid pattern essentially identical to the rat's but with temporal oscillations that did not match, effectively ruling out the oscillatory-interference class of models and strengthening the network account the Mosers had favoured. Whether grid-cell-like signals in humans carry the same function is still contested, since most human evidence comes from indirect functional imaging rather than single-cell recordings.

Whether the grid is best described as a map or as a probe has become an open question, and it is Moser's own laboratory that opened it. If grid cells spend much of their time sampling locations the animal does not occupy — including places it has never visited — then the hexagonal lattice is one component of a larger sampling process rather than the whole mechanism, and models that treat the grid purely as a position readout describe a time-averaged version of something considerably faster. This sits awkwardly beside the earlier revisionist work: the grid was first qualified as less universal than claimed because it is sheared by the geometry of the enclosure, and is now qualified again as less static than claimed.

The most interesting counter-argument is one the Mosers themselves supplied. In an early biographical account of the discovery, Edvard Moser recorded that for several weeks the team could not tell whether the hexagonal pattern was a genuine property of the cells or a recording artefact, and that only convergence across cells, animals and enclosures settled the question. That is a fair description of how the claim was made to hold, and it also defines the terms on which it was later revised: none of the subsequent challenges overturn the existence of the cells, but they do constrain how much of spatial cognition the grid map can be asked to explain on its own.

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References

Hafting, T., Fyhn, M., Molden, S., Moser, M.-B., & Moser, E. I. (2005). Microstructure of a spatial map in the entorhinal cortex. Nature, 436(7052), 801-806.