When Paul Gauguin left Paris for Tahiti in 1891, he did so in search of a simpler life. Seven years later, the artist completed his self-described masterpiece, a four-and-a-half by twelve-foot exploration of the young, the old, the human race, the animals, the Beyond. Inscribed in the upper left corner of the canvas is a title of sorts: D’où Venons-Nous / Que Sommes-Nous / Où Allons-Nous—Where do we come from? What are we? Where are we going? Gauguin may have found a simpler life, but he wasn’t asking the easy questions.
A century later, the questions haven’t gotten any easier, but we’ve started to ask them from different angles. The new technologies of contemporary neuroscience are helping us tackle some of the questions directly, if with some degree of philosophical sterility. Earlier this week, the Nobel Foundation awarded their Prize in Physiology or Medicine to a trio of scientists “for their discoveries of cells that constitute a positioning system in the brain.” These neurons are building blocks in the question of how we know where we are. It’s this kind of basic question—this kind of burning, backward, hideously complex Möbius strip of a question—that fuels neuroscientists’ modern investigation of the self and how that self navigates the outside world.
Gauguin was no neuroscientist, but May-Britt and Edvard Moser are. There’s a chance that they could pass as your typical Norwegian couple were it not for their winning—together—the Nobel Prize. Along with John O’Keefe of University College London, with whom they share the award, the Mosers study the so-called place cells and grid cells of the hippocampus and entorhinal cortex that appear to answer this slippery question of location.
Try articulating the feeling of familiarity. It’s an odd marriage of vision and memory, conscious and subconscious. How do our brains encode being in the middle of a room, versus, say, one step to the left? How do we know that we’ve moved? Considerations like these breed the archetypal investigator looming over a rat in a maze. When you picture a scientist, you’re picturing May-Britt Moser—although the Mosers don’t use cheese in their mazes. Their rats prefer chocolate cereal.
Place cells and grid cells don’t constitute a GPS device per se, but the analogy isn’t all that bad. When your smartphone calculates your position, it doesn’t do so by pinging out a signal, waiting to hear back, and computing fancy coordinate transformations from the GPS satellites. It just sits in your hand and waits. GPS-enabled devices are completely passive in this regard—the satellites do the heavy lifting. The role of a satellite is to constantly broadcast where it is and, crucially, the time. Your phone is a receiver: If it receives a timestamp from a satellite, it knows it’s sitting somewhere on a sphere whose radius is proportional to the time it took for the message to arrive. (This is when atomic clocks come in handy, since we’re talking about the speed of light.) If the phone receives timestamps from enough satellites, it draws a dot where the spheres intersect. That’s where you are.
As it turns out, the brain’s strategy for resolving location appears to be pretty similar. When O’Keefe discovered place cells in the 1970s, the result was counterintuitive: These were single neurons that appeared to activate when a rat was at a specific position on a table. How could a system as efficient as a brain afford to encode individual locations? Surely we didn’t need to remember every square foot of land we’d ever stood on. The finding must have been a fluke.
Thirty years later, the Mosers, who direct the Kavli Institute for Systems Neuroscience and Centre for Neural Computation in Norway, reported a group of cells that seem to solve the problem. Grid cells fire when an animal is at a location that lines up with a mental map of triangles spaced out in a hexagonal grid. (There’s the mark of the brain’s efficiency that everyone was looking for.) These hexagonal mental maps vary in orientation, size, and position relative to a wall. When a handful of them fire at once, a given place cell receiving their outputs will respond: Enough satellites have sent out a timestamp, and your brain has drawn its dot on the map.
Where are we going?
I was among a raving herd of neuroscientists that heard Dr. Moser—Edvard, that is—speak in Oxford in March. Moser is charismatic and measured but clearly proud of and excited by his and his wife’s work. He comes across as a man who’s happy pursuing the questions he wants to pursue and telling us about what he’s found.
Neuroscience is the study of simple questions with difficult answers. How and why did our cortex develop the way it did? (Where do we come from?) Which cognitive abilities separate us from other animals? (What are we?) How do we learn, how do we teach, and how will these processes change as we figure out how to really take advantage of them? Where Are We Going? inscribed Gauguin. We’re still working out most of these questions. In the meantime, our new Laureates are helping us understand where we are.
Photo: Paul Gauguin [Public domain], via Wikimedia Commons