Featured Research

from universities, journals, and other organizations

Going places: Rat brain 'GPS' maps routes to rewards

Date:
April 17, 2013
Source:
Johns Hopkins Medicine
Summary:
Studying rats' ability to navigate familiar territory, scientists found that the hippocampus uses remembered spatial information to imagine routes the rats then follow. Their discovery has implications for understanding why hippocampal damage disrupts specific types of memory and learning in people with Alzheimer's disease and age-related cognitive decline. And because these mental trajectories guide the rats' behavior, the research model may be useful in future studies on higher-level tasks, such as decision-making.

Unique combinations of the brain's place cells fire (red lights) in sequence to represent each part of the path (A, B, C, D) that the rat will take. This image was compiled over a few milliseconds.
Credit: David Foster, courtesy of Nature

While studying rats' ability to navigate familiar territory, Johns Hopkins scientists found that one particular brain structure uses remembered spatial information to imagine routes the rats then follow. Their discovery has implications for understanding why damage to that structure, called the hippocampus, disrupts specific types of memory and learning in people with Alzheimer's disease and age-related cognitive decline. And because these mental trajectories guide the rats' behavior, the research model the scientists developed may be useful in future studies on higher-level tasks, such as decision-making.

The details of their work are scheduled for publication online in the journal Nature on April 17.

"For the first time, we believe we have evidence that before a rat returns to an important place, it actually plans out its path," says David Foster, Ph.D., assistant professor of neuroscience at the Johns Hopkins University School of Medicine. "The rat finds that location in its mind's eye and knows how to get there."

Foster and his team found that, at least for the purposes of navigation, the "mind's eye" is located in the hippocampus, which is composed of two banana-shaped segments under the cerebral cortex on both sides of the brain. It is best known for creating memories. In people with Alzheimer's, it is one of the first parts of the brain to sustain damage.

The Foster lab experiments focused on a group of neurons in the hippocampus called place cells because they are known to fire when animals are at a given location within a given environment. What was not known, Foster says, was how and when the brain uses that information.

By miniaturizing an existing technology, Foster and a postdoc in his lab, Brad Pfeiffer, Ph.D., were able to implant 20 microwires into each side of the hippocampus of four rats. The tiny wires let them record electrical activity from as many as 250 individual place cells at the same time, more than ever achieved before.

Over a two-week training period, the rats became familiar with the testing area which was surrounded by a variety of objects, so that the rats could tell where they were in relation to the objects outside. The space was 2 meters square with 36 tiny "dishes" placed at regular intervals in a grid. A single dish at a time would be filled with the rats' reward: liquid chocolate.

The rats' navigation tests involved as many as 40 sets of alternating "odd" and "even" trials per day. The odd trials required the rats to "forage" through the arena to find a chocolate-filled dish in a random location; the even trials required the rats to return each time to a "home" dish to receive their reward. While the rats fulfilled their tasks, the researchers recorded the firing of their place cells.

They found that as a rat travels randomly through the box without knowing where it needs to go, different combinations of place cells fire at each location along its path. The same set of cells fires every time the rat travels the same spot. These unique combinations of firings "mark" each spot in the rat's brain and can be reconstructed into what seems like a virtual map, when needed.

When a rat is about to go to a specific location, e.g., "home," place cells in its hippocampus fire in a sequence that creates a predictive path, which the rat then follows, somewhat like Hansel and Gretel following an imagined bread crumb trail.

Foster says that "unlike a Hansel and Gretel bread crumb trail, which only allows you to leave by the same route by which you entered, the rats' memories of their surroundings are flexible and can be reconstructed in a way that allows them to 'picture' how to quickly get from point A to point B." In order to do this, he says, the rats must already be familiar with the "terrain" between point A and point B, but, like a GPS, they don't have to have previously started at point A with the goal of reaching point B.

Foster says the elderly can get lost easily, and research on aged mice shows that their place cells can fail to distinguish between different environments. His team's research suggests that defective place cells would also affect a person's ability to "look ahead" in their imaginations to predict a way home. Similarly, he says, higher-order brain functions, like problem solving, also require people to "look ahead" and imagine themselves in a different scenario.

"The hippocampus seems to be directing the movement of the rats, making decisions for them in real time," says Foster. "Our model allows us to see this happening in a way that's not been possible before. Our next question is, what will these place cells do when we put obstacles in the rats' paths?"

This work was supported by grants from the National Institute of Mental Health (MH085823), the Alfred P. Sloan Foundation and the Brain & Behavior Research Foundation (NARSAD Young Investigator Grant).


Story Source:

The above story is based on materials provided by Johns Hopkins Medicine. Note: Materials may be edited for content and length.


Journal Reference:

  1. Brad E. Pfeiffer, David J. Foster. Hippocampal place-cell sequences depict future paths to remembered goals. Nature, 2013; DOI: 10.1038/nature12112

Cite This Page:

Johns Hopkins Medicine. "Going places: Rat brain 'GPS' maps routes to rewards." ScienceDaily. ScienceDaily, 17 April 2013. <www.sciencedaily.com/releases/2013/04/130417131811.htm>.
Johns Hopkins Medicine. (2013, April 17). Going places: Rat brain 'GPS' maps routes to rewards. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2013/04/130417131811.htm
Johns Hopkins Medicine. "Going places: Rat brain 'GPS' maps routes to rewards." ScienceDaily. www.sciencedaily.com/releases/2013/04/130417131811.htm (accessed July 23, 2014).

Share This




More Mind & Brain News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Do Obese Women Have 'Food Learning Impairment'?

Do Obese Women Have 'Food Learning Impairment'?

Newsy (July 18, 2014) Yale researchers tested 135 men and women, and it was only obese women who were deemed to have "impaired associative learning." Video provided by Newsy
Powered by NewsLook.com
Does Mixing Alcohol and Energy Drinks Boost Urge To Drink?

Does Mixing Alcohol and Energy Drinks Boost Urge To Drink?

Newsy (July 18, 2014) A new study suggests that mixing alcohol with energy drinks makes you want to keep the party going. Video provided by Newsy
Powered by NewsLook.com
Pot Cooking Class Teaches Responsible Eating

Pot Cooking Class Teaches Responsible Eating

AP (July 18, 2014) Following the nationwide trend of eased restrictions on marijuana use, pot edibles are growing in popularity. One Boston-area cooking class is teaching people how to eat pot responsibly. (July 18) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins