Brain activity may mark the beginning of memories

April 14, 2014
brain
White matter fiber architecture of the brain. Credit: Human Connectome Project.

By tracking brain activity when an animal stops to look around its environment, neuroscientists at the Johns Hopkins University believe they can mark the birth of a memory.

Using lab rats on a circular track, James Knierim, professor of neuroscience in the Zanvyl Krieger Mind/Brain Institute at Johns Hopkins, and a team of brain scientists noticed that the rats frequently paused to inspect their environment with head movements as they ran. The scientists found that this behavior activated a place cell in their brain, which helps the animal construct a cognitive map, a pattern of activity in the brain that reflects the animal's internal representation of its environment.

In a paper recently published in the journal Nature Neuroscience, the researchers state that when the rodents passed that same area of the track seconds later, fired again, a neural acknowledgement that the moment has imprinted itself in the brain's cognitive map in the .

The hippocampus is the brain's warehouse for long- and short-term processing of episodic memories, such as memories of a specific experience like a trip to Maine or a recent dinner. What no one knew was what happens in the hippocampus the moment an experience imprints itself as a memory.

"This is like seeing the brain form memory traces in real time," said Knierim, senior author of the research. "Seeing for the first time the brain creating a spatial firing field tied to a specific behavioral experience suggests that the map can be updated rapidly and robustly to lay down a memory of that experience."

A place cell is a type of neuron within the hippocampus that becomes active when an animal or human enters a particular place in its environment. The activation of the cells

helps create a spatial framework much like a map, that allows humans and animals to know where they are in any given location. Place cells can also act like neural flags that "mark" an experience on the map, like a pin that you drop on Google maps to mark the location of a restaurant.

"We believe that the spatial coordinates of the map are delivered to the hippocampus by one brain pathway, and the information about the things that populate the map, like the restaurant, are delivered by a separate pathway," Knierim said. "When you experience a new item in the environment, the hippocampus combines these inputs to create a new spatial marker of that experience."

In the experiments, researchers placed tiny wires in the brains of the rats to monitor when and where increased as they moved along the track in search of chocolate rewards. About every seven seconds, the rats stopped moving forward and turned their heads to the perimeter of the room as they investigated the different landmarks, behavior called "head-scanning."

"We found that many cells that were previously silent would suddenly start firing during a specific head-scanning event," Knierim said. "On the very next lap around the track, many of these cells had a brand new place field at that exact same location and this place field remained usually for the rest of the laps. We believe that this new place field marks the site of the head scan and allows the brain to form a memory of what it was that the rat experienced during the head scan."

Knierim said the formation and stability of place fields and the newly activated place cells requires further study. The research is primarily intended to understand how memories are formed and retrieved under normal circumstances, but it could be applicable to learning more about people with brain trauma or hippocampal damage due to aging or Alzheimer's.

"There are strong indications that humans and rats share the same spatial mapping functions of the hippocampus, and that these maps are intimately related to how we organize and store our memories of prior life events," Knierim said. "Since the hippocampus and surrounding brain areas are the first parts of the affected in Alzheimer's, we think that these studies may lend some insight into the severe memory loss that characterizes the early stages of this disease."

Explore further: Memories are 'geotagged' with spatial information, study finds

Related Stories

Memories are 'geotagged' with spatial information, study finds

November 28, 2013
Using a video game in which people navigate through a virtual town delivering objects to specific locations, a team of neuroscientists from the University of Pennsylvania and Freiburg University has discovered how brain cells ...

Experience puts the personal stamp on a place in memory

August 22, 2011
Seeing and exploring both are necessary for stability in a person's episodic memory when taking in a new experience, say University of Oregon researchers.

Neurons in the rat brain use a preexisting set of firing sequences to encode future navigational experiences

July 25, 2013
Specialized neurons called place cells, located in the hippocampus region of the brain, fire when an animal is in a particular location in its environment, and it is the linear sequence of their firing that encodes in the ...

Brain mapping reveals neurological basis of decision-making in rats

March 20, 2013
Scientists at UC San Francisco have discovered how memory recall is linked to decision-making in rats, showing that measurable activity in one part of the brain occurs when rats in a maze are playing out memories that help ...

Study reveals how the brain links memories of sequential events

January 23, 2014
Suppose you heard the sound of skidding tires, followed by a car crash. The next time you heard such a skid, you might cringe in fear, expecting a crash to follow—suggesting that somehow, your brain had linked those two ...

Recommended for you

'Residual echo' of ancient humans in scans may hold clues to mental disorders

July 26, 2017
Researchers at the National Institute of Mental Health (NIMH) have produced the first direct evidence that parts of our brains implicated in mental disorders may be shaped by a "residual echo" from our ancient past. The more ...

Laser used to reawaken lost memories in mice with Alzheimer's disease

July 26, 2017
(Medical Xpress)—A team of researchers at Columbia University has found that applying a laser to the part of a mouse brain used for memory storage caused the mice to recall memories lost due to a mouse version of Alzheimer's ...

Cellular roots of anxiety identified

July 26, 2017
From students stressing over exams to workers facing possible layoffs, worrying about the future is a normal and universal experience. But when people's anticipation of bad things to come starts interfering with daily life, ...

Cognitive cross-training enhances learning, study finds

July 25, 2017
Just as athletes cross-train to improve physical skills, those wanting to enhance cognitive skills can benefit from multiple ways of exercising the brain, according to a comprehensive new study from University of Illinois ...

Brain disease seen in most football players in large report

July 25, 2017
Research on 202 former football players found evidence of a brain disease linked to repeated head blows in nearly all of them, from athletes in the National Football League, college and even high school.

Zebrafish study reveals clues to healing spinal cord injuries

July 25, 2017
Fresh insights into how zebrafish repair their nerve connections could hold clues to new therapies for people with spinal cord injuries.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

russell_russell
not rated yet Apr 14, 2014
Severe memory loss for the disease mentioned in the article can be explained as gene expressions of cells where the gene expressions of the effected cells are no longer alterable to a change in expressions. An analogy to a computer is helpful: Imagine screen lock and everything else works to aid what you see - the greater the loss of memory the less a world will change for you.

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.