The previously unknown memory mechanism occupies an intermediate position between short-term and long-term.
Scientists stumbled upon traces of memories at that intermediate moment, when they had already left short-term memory, but had not yet been preserved in long-term memory. This is reported by an article published in the journal Science.
New memories are stored in short-term memory, the neurons of which continue to fire for seconds. However, after a few hours, sufficiently important events and information are consolidated, passing into long-term memory associated with the appearance, change and consolidation of connections between neurons. The team of the University of Wisconsin professor Bradley Postle managed to hit the trail of the third, intermediate form of memory - the one where memories appear after they have left the short-term memory, but have not yet been "written" into the long-term memory.
To a group of subjects, scientists showed a series of images, including faces, words, or just circles. At the same time, with the help of a tomograph, it was possible to register different patterns of activity of neurons in their brain, and a computer algorithm with elements of machine learning deciphered them, linking one or another specific activity with the corresponding image. At the next stage, images in paired combinations (for example, a face and a circle) were already present on the visual stimuli, and the participants in the experiment were asked to focus on only one of them and “throw the second out of their heads”.
Electroencephalography has shown that when such a double picture is first shown, neural patterns corresponding to both objects are activated. Then, when the subject focuses on one of them, the activity associated with the second quickly drops to baseline - as if he completely forgot about this object and really "threw" it out of his head and from short-term memory. However, as soon as scientists asked to remember about him, this activity immediately returned, as if emerging from oblivion.
Curious about this "evocation of memories," Powtle and his colleagues turned to a non-invasive method of transcranial magnetic stimulation - the targeted firing of neurons with weak magnetic fields from electrodes attached to the scalp. They repeated the experiment, but this time, as soon as the pattern of the second object died out on the encephalogram, a single excitatory impulse was applied to the brain, which led to a rapid return of this pattern of activity.
The authors believe that they managed to find a kind of "limb", which contains quite important memories that have left short-term memory, but have not yet been preserved in long-term memory. How this mechanism, which scientists have called “priority short-term memory,” functions is still completely unclear. In the near future, scientists plan to find out at least the basic principles of its work, and understand whether they are closer to the excitation of neural patterns, characteristic of short-term memory, or to plastic changes in synapses, as in long-term memory.
Yaroslav Rybakov
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