Featured Research

from universities, journals, and other organizations

Specific Neurons Involved In Memory Formation Identified

Date:
September 6, 2007
Source:
Scripps Research Institute
Summary:
Scientists have unlocked one of the secrets of how memory is formed. Working with a unique breed of transgenic mice, the new study has shown for the first time that the same neurons activated during fear conditioning are, in fact, reactivated during memory retrieval. The findings could potentially be used to uncover precisely how drugs such as antidepressants work in the brain, allowing clinicians to more accurately evaluate various treatment options.

In a remarkable new study, scientists at The Scripps Research Institute have unlocked one of the secrets of how memory is formed. Working with a unique breed of transgenic mice, the new study has shown for the first time that the same neurons activated during fear conditioning are, in fact, reactivated during memory retrieval.

The findings could potentially be used to uncover precisely how drugs such as antidepressants work in the brain, allowing clinicians to more accurately evaluate various treatment options.

"Our study provides the answers to some basic questions," said Mark Mayford, whose laboratory conducted the groundbreaking study. "We show that when you learn, and when you recall what you've learned, you reactivate the same neurons used during the original experience. While some studies have shown which region of the brain is active during learning and recall, we've now shown this at the level of individual neurons."

The new results suggest that the affected neurons evolved stable synaptic changes, giving them a capacity for reactivation by conditioned stimulus for at least three days. The study concluded that the reactivated neurons were likely a component of a stable engram or memory trace for conditioned fear.

Memories are presumably stored in subgroups of neurons that are activated in response to various sensory experiences, the study said. Previously, some encoding of memories in complex neuronal networks had been identified with electrophysiological recordings, and similar approaches have identified neurons with firing properties temporally linked to various aspects of learned task performance.

But, Mayford noted, this is like knowing only that a computer is turned on. The new study shows precisely which circuits are active during a specific memory formation.

"We found neurons in the basolateral amygdala that were activated during fear conditioning and were reactivated during memory retrieval," Mayford said. "The number of reactivated neurons correlated with the behavioral expression of that fear memory in the mice themselves, which indicates a stable correlation between these neurons and memory."

The basolateral amygdala is the part of the brain believed to be responsible for memories involving emotional arousal.

An innovative mouse

The new study utilized a unique transgenic mouse (TetTag mouse) that enabled scientists to genetically tag individual neurons activated during a given time frame. The tag can be used for the direct comparison of neuronal activity at two distinct and widely spaced points in time.

(The name TetTag comes from the technology itself; it combines elements of the tetracycline-transactivator system. Gene expression is controlled in these transgenic mice through exposure to tetracycline or derivatives such as doxycycline.)

This novel technology can be used with free roaming mice, enabling the scientists to record and measure the correlation between neuronal activity and any behavioral expression of a specific memory. Moreover, the study noted, the technology requires only basic laboratory equipment, which is generally available to most researchers.

"The TetTag mouse allows us to put genes into neurons that have been activated by an environmental stimulus," Mayford said. "Basically, we can put any gene we want into those neurons activated by fear, and this gives us genetic control over very specific circuits in the brain."

The reason fear and anxiety were used as the activating experience, Mayford said, is because fear is an ancient and fundamental emotion" "We know that mice feel fear; we don't know if they feel joy. In the wild, you can survive without joy, but you don't live very long without fear."

The ability to genetically manipulate these activated neurons should allow a better and more precise understanding of the underlying molecular mechanisms of memory encoding within a particular neuronal network.

This might one day translate into a clinical advantage for treating patients suffering from disorders such as depression, Mayford said.

"Antidepressants don't work the same in every individual," he said, "so our genetic tagging technique could potentially help clinicians evaluate treatment by showing how an individual's brain works at two different times during treatment-where and how the drug is affecting specific neurons."

The new study was published in the August 31, 2007, edition of the journal Science. Other authors of the Science study, "Localization of a Stable Neural Correlate of Associative Memory," were Leon G. Reijmers, Brian L. Perkins, and Naoki Matsuo of The Scripps Research Institute.

The study was supported by the National Institutes of Health.


Story Source:

The above story is based on materials provided by Scripps Research Institute. Note: Materials may be edited for content and length.


Cite This Page:

Scripps Research Institute. "Specific Neurons Involved In Memory Formation Identified." ScienceDaily. ScienceDaily, 6 September 2007. <www.sciencedaily.com/releases/2007/09/070905152831.htm>.
Scripps Research Institute. (2007, September 6). Specific Neurons Involved In Memory Formation Identified. ScienceDaily. Retrieved September 1, 2014 from www.sciencedaily.com/releases/2007/09/070905152831.htm
Scripps Research Institute. "Specific Neurons Involved In Memory Formation Identified." ScienceDaily. www.sciencedaily.com/releases/2007/09/070905152831.htm (accessed September 1, 2014).

Share This




More Plants & Animals News

Monday, September 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Washington Wildlife Center Goes Nuts Over Baby Squirrels

Washington Wildlife Center Goes Nuts Over Baby Squirrels

Reuters - US Online Video (Aug. 30, 2014) An animal rescue in Washington state receives an influx of orphaned squirrels, keeping workers busy as they nurse them back to health. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Newsy (Aug. 29, 2014) In a new study, a promising experimental treatment for Ebola managed to cure a group of infected macaque monkeys. Video provided by Newsy
Powered by NewsLook.com
Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) 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