The brain uses a secret code to create a key type of memory.
This type of memory, called working memory, allows people to temporarily hold on to and manipulate information for short periods of time.
You use working memory when you look up a phone number and then remember the sequence of digits in order to dial, or when you ask a friend for directions to a restaurant and then keep track of the turns as you drive.
An assistant professor of psychology and neuroscience at Florida State University told Live Science that the new work represents a fundamental step forward in the study of working memory.
Scientists have wondered how and where the brain codes memories.
One theory suggests that working memory relies on special stores in the brain, separate from where the brain handles incoming sensory information from the eyes, nose, or long-term memories.
The opposing theory suggests that there are no special storehouses.
When sensory and motor representations are kept around as we link the past to the future, working memory is an emerging phenomenon.
When you first read a phone number, your brain cells light up, and when you run through that number again and again, your brain cells light up as well.
Your brain exaggerates memories to remember them better.
The new study challenges both of the theories.
Rather than reflecting what happens during perception or relying on special memory storehouses, working memory seems to operate one step up from sensory information gathering and sums up that information in a relatively simple code.
There have been clues for decades that what we store in working memory might be different from what we see.
The brain scanning technique fMRI can be used to measure changes in blood flow to different parts of the brain. fMRI provides an indirect measure of brain cell activity because active brain cells need more energy and oxygen.
The team scanned the brains of nine volunteers while they performed a task that engaged their working memory, and the two study authors also completed the task and contributed brain scans to the study.
In one of the trials, the participants were shown a circle on a screen for four seconds and then the graphic disappeared and the participants were asked to recall the angle of the slashes.
In other trials, the participants were asked to recall the exact angle of the dot cloud's motion after viewing a cloud of moving dots that all shifted in the same direction.
We predicted that participants would code the complex stimuli into something simpler and relevant to the task at hand.
The researchers theorize that the brain activity of participants would reflect the specific attributes of the graphics.
The brain scans data was analyzed by the team.
The famous memory trick by the detective, "Sherlock Holmes," really works.
The researchers created a topographical map of the brain activity using computer modeling.
Brain cells that process visual data have a specific receptive field, meaning they respond to stimuli in a specific area of the visual field.
The team took these receptive fields into account in their models, which helped them understand how the participants brain activity related to what they saw on-screen during the memory task.
The analysis showed that the brain only needed the relevant information for the task at hand and not the fine details of each graphic.
When viewed on the maps, the brain activity used to generate this information looked like a straight line.
Depending on the graphic the participants had been shown, the angle of the line would match the orientation of the gratings or the angle of the dot cloud.
The line-like brain activity patterns appeared in the visual cortex, where the brain receives and processes visual information, and the parietal cortex, a key region for memory processing and storage.
The brain settled on using lines to represent the images.
It is the fact that the representation has been changed.
One limitation of the study is that the team used simplistic graphics, which do not reflect the complexity of the real world.
This limitation extends to many studies of working memory, and Nee uses similar simple graphics in his own research.
The field will need to move towards richer stimuli that better match our natural visual experiences to bring us from the laboratory to practical utility.
He said that the new study still provides a novel insight into what it means to hold something online in mind for the future.
Working memory is a bridge between perception and action when it comes to a phone number.
This study, in identifying a representational format that resembles neither what was perceived nor what will be done but can be clearly read out from visual signals, offers an unprecedented look into this mysterious intermediate zone between perception and action.
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The article was published by Live Science. The original article can be found here.
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