Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New insight into how brain performs 'mental time travel'

18.02.2015

In Proust's novel Recollection of Things Past, the distinctive smell of a lemon madeleine launches the narrator on a long, involved reminiscence of his past that fills seven chapters.

It is an extreme example of what neuroscientists term "mental time travel" - the recollection of memories so rich in detail regarding the time and place of an original experience that it is much like traveling through time.


This is a cartoon of memory recall.

Credit: Sean Polyn & Keith Wood, Vanderbilt University

In a paper published Feb. 18 in the Journal of Neuroscience, a team of Vanderbilt scientists shed new light on how the brain processes these elaborate memories by analyzing the brain activity of individuals performing a simple memory recollection task. The researchers found that they can use the activity patterns in a specific region of the brain to substantially improve their ability to predict the order in which the participants recall information that they have recently studied.

"It's extremely important that we understand what different brain regions are doing as we search through our memories," said Assistant Professor of Psychology Sean Polyn who headed the study. "Diseases like Alzheimer's and epilepsy are devastating to memory, and this information can help us develop treatments to preserve patients' memories, and identify adverse effects that new psychotropic drugs may have on people's memory."

Scientists have known for some time that a portion of the brain called the medial temporal lobe plays a central role in memory because injuries to the MTL cause amnesia and other memory-related problems. However, they have not been able to answer the question: How does the brain control the fidelity of an individual memory?

Of course, not all memories are recalled equally. High fidelity Proustian memories are at one end of the spectrum. At the other are bits of information that a person remembers clearly, but in complete isolation, without any accompanying details. Polyn, working with doctoral students James Kragel and Neal Morton (who is now at the University of Texas, Austin), has developed a model that accounts for how the structures in the MTL support memory retrieval. They have found that the anterior region of the MTL signals that a memory is being retrieved, but doesn't indicate how detailed it is. However, when the posterior region of the MTL becomes active it indicates that the person is experiencing a "time travel" memory accompanied by considerable detail.

The researchers tested their model in an experiment with 20 participants (seven male and 13 female) between 18 and 35 years of age. They were put in an fMRI brain scanner and given a list of 24 names of common objects like horse, boat and window. Depending on the object they were asked to decide if it was big or small, animate or inanimate. (The purpose of the question was to make them concentrate on the words.) After a brief pause, they were asked to recall the words they had just studied in the order they occurred naturally.

The researchers found that when a participant's brain scan indicated that they recalled an object with high fidelity, then their next response was likely to be the next item on the list. However, when the brain scan indicated that the object was an isolated recollection, then the next object the person recalled could come from anywhere on the list.

For example, the participants might be asked to study the words "horse, window, robot and boat," in that order. An individual who experienced a time-travel experience when he or she recalled the word "horse," would be very likely to recall "window" immediately afterward. If, on the other hand, the person's memory of "horse" was low fidelity, his or her next response might instead be the more distant word, "boat."

Polyn's group had previously developed a model of memory search that could be used to predict the order in which people would retrieve these items from memory. For example, the model predicts that people will tend to first recall the items from the end of the list, and if an item from the middle of the list is recalled, the next recollection is likely to come from a nearby list position.

"This model was much better than chance at predicting what a person would recall next, but when we told the model what a person's brain activity was at the moment they recalled a particular item, the model became much better at predicting which item would be recalled next," Polyn said. "This demonstrates that the brain stamps memories with a temporal code. These time-travel recollections allow the brain to retrieve that temporal code, which makes memories for nearby things more accessible, in this case the next item in the list."

The temporal code acts something like the time stamp that computers put on files. When you search for files stamped with a specific date and time, you retrieve all the files saved at the time you specify. Time-travel memory acts in much the same way, through a process psychologists call "reinstatement". This process is even more flexible than a computer, in that the temporal code can help you retrieve not just memories from the exact same time, but memories nearby in time, as well.

When a strong memory is formed, it may include information about the sights, sounds, smells, emotions, and other information that was present at the time of the experience. All of this information becomes temporally linked, and time-travel memory allows a person to bring it back to mind, as when Proust smelled his famous madeleine cake.

Polyn's memory model is an example of a new generation of brain simulations that are attempting to link brain activity with specific cognitive functions.

###

The research was funded in part by National Science Foundation grant 1157432.

David Salisbury | Vanderbilt University

More articles from Social Sciences:

nachricht Fixating on faces
26.01.2017 | California Institute of Technology

nachricht Internet use in class tied to lower test scores
16.12.2016 | Michigan State University

All articles from Social Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>