Many drivers now depend on a global positioning system (GPS) to navigate roads in unfamiliar towns or subdivisions. But the brain has its own GPS-like system. It helps people and other animals orient themselves in their environment. For figuring out how this brain network works, the Nobel Prize committee granted this year’s award in Physiology or Medicine to three neuroscientists. The announcement was made on October 6.
John O’Keefe of University College London in England will receive half of the award — which this year totals about $1.1 million. The other half goes to the husband-and-wife duo May-Britt and Edvard Moser. The Mosers work at the Norwegian University of Science and Technology in Trondheim, Norway.
The work by O’Keefe and the Mosers relied on rats. And with good reason. They’re some of the best navigators around.
The scientists discovered the nerve cells that keep track of a rat’s location. That provided a strikingly clear example of how the brain makes sense of its environment. The discovery of these navigational cells is “is one of the most exciting stories in brain and cognitive sciences today,” says Barbara Landau. A cognitive scientist, she works at Johns Hopkins University in Baltimore, Md.
“They are really good scientists in terms of seeking out truth in the world,” says Joshua Jacobs. He’s a neuroscientist of Drexel University in Philadelphia, Pa. What’s more, he adds, “These are delightful people.”
The science behind it all
A brain region known as the hippocampus is central to memory. In 1971, O’Keefe found that certain cells in a rat’s brain become active only when the animal is in a particular spot. These place cells allow an animal to form an internal map of its surroundings. O’Keefe used implanted electrodes to record the behavior of these neurons (nerve cells) as the rats moved freely about an area.
Decades later, the Mosers discovered grid cells in a nearby brain area. It’s called the entorhinal cortex. Its grid cells fired off signals when a rat passed through certain locations spaced at regular intervals.
These grid cells become active as an animal moves within its in the environment, pacing off the distances. The turned-on cells fire, mapping out a pattern that resembles a Chinese checkers board or the hexagonal cells of a honeycomb.
Other cells take note of borders and the position of the animal’s head. Together with grid cells, these others send messages to place cells in the hippocampus, the Mosers found. The resulting elaborate network of neurons allows an animal to know where it is in the world.
“This is work that’s important not just because of what it tells us about space,” says Russell Epstein. “It’s the best example we have of how information can be encoded in the nervous system,” he says. A cognitive neuroscientist, Epstein works at the University of Pennsylvania in Philadelphia.
With implanted electrodes, scientists uncovered place cells in the brains of people in 2003 and grid cells in 2013. “From what we can tell, there’s quite a bit of similarity between rats and people,” says Jacobs at Drexel, who helped find the grid cells in people.
But understanding how the brain navigates doesn’t stop at navigation. Getting a sense of where the body is in space seems an important step for developing babies, says Michael Kahana. A neuroscientist, he too works at the University of Pennsylvania. The hippocampus and the entorhinal cortex have important roles in memory. People build many memories on a scaffold of space, he says. One example: If someone eats a superb meal out at a restaurant, she will often, for instance, recall exactly which table she sat at.
These same brain regions are some of the first affected by Alzheimer’s disease. In the early stages of brain degeneration in this disorder, the ability to figure out how to get somewhere can slip away. That may be due to a loss of these navigational cells.
Alzheimer’s disease An incurable brain disease that can cause confusion, mood changes and problems with memory, language, behavior and problem solving. No cause or cure is known.
cognitive science A field that studies mental activities, such as thinking, learning, remembering and solving puzzles.
degenerate A verb for the breakdown of a system, usually a living one. A degenerative disease, for instance, is one that leads to the breakdown of a healthy heart, muscle or other tissue system — usually in a way that cannot repair itself.
electrode (in brain science) Sensors that can pick up electrical activity. (in chemistry) Materials that serve as an anode or cathode, attracting negatively or positively charged particles. Or things that serve as electrical conductors through which current leaves or enters something else.
entorhinal cortex A portion of the brain (located, broadly, behind the nose) that serves as a relay station to transmit signals between the hippocampus (memory center) and the rest of the brain. It serves as a hub in a broad network that also underpins navigation.
GPS, or global positioning system These electronic systems uses a device to calculate the position of individuals or things (in terms of latitude, longitude and elevation — or altitude) from any place on the ground or in the air. The device does this by comparing how long it takes to receive signals from different satellites.
grid (in mathematics or mapping) A network of lines that cross each other at regular intervals, forming boxes or rectangles, or an orderly field of dots that mark where each pair of lines intersect, or cross one another.
hexagon A geometric shape that has six equal sides. It takes its name from the Greek word for six.
hippocampus A seahorse-shaped region of the brain. It is thought to be the center of emotion, memory and the involuntary nervous system.
neuron or nerve cell Any of the impulse-conducting cells that make up the brain, spinal column and nervous system. These specialized cells transmit information to other neurons in the form of electrical signals.
neuroscience Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.
physiology The branch of biology that deals with the everyday functions of living organisms and how their parts function.