Brain maps help guide you through large-scale space, researchers find

Nov 03, 2009 By Robert S. Boyd

Lost? Not sure how to get home? Trying to find your way through the mall or an airport? Help is on the way, thanks to a stack of cells, or neurons, in your head. They're mostly on the left side of the brain in males, on the right in females.

Scientists have long known that a small, seahorse-shaped region in the , the hippocampus, contains called "place cells" that specialize in geography.

In recent years, working mostly with laboratory rats, they have discovered additional types of neurons in or near the hippocampus known as "grid cells," "head-direction cells" and "border cells."

Taken together, "these cells form a map of the environment," said Edvard Moser, a leading expert on at the Norwegian University of Science and Technology in Trondheim, Norway.

The brain maps tell animals, including humans, where they are, how they got there and how to navigate to their next destinations, neuroscientists say.

"The ability to find one's way through a large-scale space such as an airport, college campus or city neighborhood is essential for successful functioning in the modern world," said Russell Epstein, a neuroscientist at the University of Pennsylvania in Philadelphia. "When we are lost and need to re-establish our general location, scene recognition mechanisms ... are likely to be crucial, potentially enabling the correct 'map' to be selected in the hippocampus."

Matthew Wilson, a neurobiologist at the Massachusetts Institute of Technology in Cambridge, compared the hippocampus to a computer hard drive. Instead of electronic bits and bytes, it contains millions of neurons that store memories of places, people, things and events.

Neuroscientists say that brain mapping cells "fire" -- that is, release tiny electric charges -- when they sense they're in specific locations or headed in certain directions.

Border cells, for example, light up when they're close to walls or other boundaries. Moser called them "the brain's border patrol."

In a report last December in the journal Science, Trygve Solstad, a researcher in Moser's lab, outlined how the various cell groups work: "Place cells fire when we pass through fixed locations, letting us know where we are; head-direction cells fire when we face particular directions, acting as a compass, and grid cells fire when we're at specific points on a hexagonal grid that the brain superimposes on our surroundings."

Moser likened the stack of mapping neurons to a deck of cards.

"The maps are stored as extremely thin cards in a deck in the hippocampus, the area that is regarded as the brain's memory focal point," he said. "The deck is sorted by rank, so that the fine-grained detail maps are located at the top, with the biggest, most coarsely drawn maps further down in the deck."

It's much easier for researchers to experiment with laboratory mice and rats than with people. They make the little animals run along tracks, navigate mazes or swim pools to find rewards. As they run or swim, brain cells fire as they pass over each place in their internal maps. The order of the firings shows the creatures' paths.

The firing pattern "reflects both the animals' present spatial position in the environment and the specific trajectory taken to reach that position," Douglas Nitz, a cognitive scientist at the University of California at San Diego, wrote in the Oct. 15 issue of Nature.

"Cells care about the sequence, the path of motion," MIT's Wilson said.

"There is also evidence for such maps in humans, although much less," Moser said. In all mammals, "the wiring diagram is so similar that there are all kinds of reasons to believe that the same neural firing patterns are generated."

Researchers on humans used to have to rely on sticking sensors in the brains of epileptic patients or studying the effects of brain injuries in the hippocampal area.

Now they're increasingly using "virtual reality" environments, like those found in computer games.

For example, Eleanor Maguire, an expert on the hippocampus at the Wellcome Trust for Brain Imaging in London, put people in a functional magnetic resonance imaging machine to observe which neurons fired as they navigated through a simplified virtual-reality maze.

"Remarkably, we could accurately predict the position of an individual within this environment solely from the pattern of activity in his hippocampus," Maguire reported in the April 14 edition of Current Biology.

Researchers have identified gender differences in the ways that brain maps work in males and females.

"Female animals use landmarks as external cues," Wilson said. "Male animals use internal, spatial maps."

According to Georg Groen, a psychiatrist at the University of Ulm, Germany, men and women who are searching for a way out of a complex, three-dimensional virtual reality maze use different parts of their brains. Males activate the left hippocampus, while females use other regions on the right side, Groen said.

Incidentally, Maguire acknowledged, "men were significantly faster than women at finding a way out of the maze."
___

(c) 2009, McClatchy-Tribune Information Services.
Visit the McClatchy Washington Bureau on the World Wide Web at www.mcclatchydc.com

Explore further: 'Trigger' for stress processes discovered in the brain

add to favorites email to friend print save as pdf

Related Stories

The 'satellite navigation' in our brains

Sep 11, 2008

Our brains contain their own navigation system much like satellite navigation ("sat-nav"), with in-built maps, grids and compasses, neuroscientist Dr Hugo Spiers told the BA Festival of Science at the University of Liverpool ...

Do mammals think in 3-D?

Jul 14, 2008

A team of neuroscientists at University College London (UCL) has begun to discover how the brain maps three-dimensional space. The work could one day aid in the understanding and treatment of Alzheimer’s disease, which ...

Stem cells are good for the brain

Jul 15, 2008

For some years, scientists have been speculating over why stem cells exist in the brain, as brain regeneration is limited. A German team of neuroscientists believe these stem cells help keep the brain healthy and active.

Cracking the spatial memory code

Mar 12, 2009

Researchers have shown that they can tell where a person is "standing" within a virtual reality room on the basis of the pattern of activity in the brain alone. The findings, published online on March 12th in Current Biology, a Cell ...

Recommended for you

'Chatty' cells help build the brain

12 hours ago

The cerebral cortex, which controls higher processes such as perception, thought and cognition, is the most complex structure in the mammalian central nervous system. Although much is known about the intricate ...

'Trigger' for stress processes discovered in the brain

Nov 27, 2014

At the Center for Brain Research at the MedUni Vienna an important factor for stress has been identified in collaboration with the Karolinska Institutet in Stockholm (Sweden). This is the protein secretagogin ...

New research supporting stroke rehabilitation

Nov 26, 2014

Using world-leading research methods, the team of Dr David Wright and Prof Paul Holmes, working with Dr Jacqueline Williams from the Victoria University in Melbourne, studied activity in an area of the brain ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.