Researchers discover ‘secret code’ our brains use to store working visual memory

(ORDO NEWS) — The “secret code” that the brain uses to create a key type of memory has finally been cracked.

This type of memory, called working memory, allows people to temporarily hold and manipulate information for short periods of time.

Working memory is used, for example, when you look up a phone number and then briefly memorize a sequence of numbers to dial the number, or when you ask a friend for directions to a restaurant and then follow the turns as you drive there.

The new work represents a “fundamental step forward” in the study of working memory, Derek Nee, assistant professor of psychology and neuroscience at Florida State University, told Live Science in an email.

Essential Process

For decades, scientists have wondered how and where the brain encodes short-term memories.

One theory suggests that working memory relies on special “stores” in the brain, separate from where the brain processes incoming sensory information, such as from the eyes or nose, or where long-term memories are stored, such as memories of who you are with. going to prom, or fundamental knowledge gained in school, says Nee, who was not involved in the new study.

Another, opposing theory suggests that “there are no such special repositories,” Nee told Live Science.

According to this alternative theory, working memory is essentially an emergent phenomenon that occurs “when sensory and motor representations are retained, when we connect the past with the future,” Nee said.

According to this theory, when you first read a phone number, the same brain cells light up as when you read the number again in working memory.

Related articles: Your brain exaggerates memories to better remember them A new study published April 7 in the journal Neuron refutes both of these theories.

Instead of reflecting what happens during perception or relying on special memory stores, working memory seems to work one step above the collection of sensory information; it extracts only the most relevant sensory information from the environment and then summarizes that information into a relatively simple code.

“For decades, there have been hints that what we store in [working memory] may be different from what we perceive,” said study senior author Clayton Curtis, professor of psychology and neuroscience at New York University (NYU). via email in an interview with Live Science.

To unravel the mysteries of working memory, Curtis and study co-author Yuna Kwak, a doctoral student at New York University, used a brain scan called functional magnetic resonance imaging (fMRI), which measures changes in blood flow to different parts of the brain. Active brain cells require more energy and oxygen, so fMRI can indirectly measure the activity of brain cells.

The team used this method to scan the brains of nine volunteers during a task that involved their working memory; the two authors of the study also completed the task and provided brain scans for the study.

In one test, participants watched a circle of bars, or oblique lines, on a screen for about four seconds; the image then disappeared, and after 12 seconds the participants were asked to remember the angle of the oblique lines.

In other trials, participants viewed a cloud of moving dots that were all moving in the same direction and were asked to remember the exact angle at which the dot cloud moved.

“We predicted that participants would recode a complex stimulus” – a corner grid or moving dots – “into something simpler and more relevant to the task at hand,” Curtis told Live Science in an interview.

The participants were asked to pay attention only to the orientation of the oblique lines or the angle of movement of the point cloud, so the researchers assumed that their brain activity would only reflect these specific graphics attributes.

And when the team analyzed the brain scan data, that’s exactly what they found. Related: Sherlock Holmes’ famous memory trick really works.

The researchers used computer simulations to visualize the complex brain activity, creating a kind of topographic map showing the peaks and valleys of activity in different groups of brain cells.

The brain cells that process visual data have a specific “receptive field”, that is, they are activated in response to stimuli that appear in a certain area of ​​the human visual field.

The team incorporated these receptive fields into their models, which helped them understand how participants’ brain activity was related to what they saw on the screen during the memory task.

This analysis showed that instead of encoding all the fine details of each graphic image, the brain stored only the information that was necessary to solve the task.

When looking at topographic maps, the brain activity used to encode this information looked like a simple straight line.

The angle of the line corresponded to the orientation of the gratings or the angle of movement of the point cloud, depending on which image was shown to the participants.

These linear patterns of brain activity occurred in the visual cortex, where the brain receives and processes visual information, and in the parietal cortex, a key area for memory processing and storage.

What matters is not that the brain chose to use lines to represent images.

“The point is that the representation was abstracted away from the grids [or] movement towards something else,” Nee said.

One limitation of the study is that the team used very simplified graphics that don’t necessarily reflect the visual complexity of the real world, Nee noted.

This limitation applies to many studies of working memory, and Nee said he uses similarly simple charts in his own studies.

“To move from laboratory research to practical applications, it is necessary to move to richer stimuli that better match our natural visual experience,” he said.

But despite this, the new study still “provides a new understanding of what it means to keep something online in memory for the future,” he said.

Working memory essentially acts as a bridge between perception (when we read a phone number) and action (when we dial that number).

“This study, by identifying a presentation format that is neither what was perceived nor what will be done, but can be clearly read from visual cues, offers an unparalleled insight into this enigmatic intermediate zone between perception and action,” Ni said.

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