Research study offers brand-new insights into how our visual memories are saved.
A team of scientists has actually found how working memory is “formatted”– a finding that enhances our understanding of how visual memories are kept..
” For decades scientists have actually questioned the nature of the neural representations that support our working memory,” discusses Clayton Curtis, professor of psychology and neural science at New York University and the senior author of the paper, which appears in the journal Neuron. “In this research study, we used both experimental and analytical techniques to expose the format of working memory representations in the brain.”.
Its been known for years that we re-code visual information about letters and numbers into phonological or sound-based codes utilized for verbal working memory. When you see a string of digits of a phone number, you do not keep that visual info till you end up calling the number. To explore this, the experimenters measured brain activity with practical magnetic resonance imaging (fMRI) while individuals carried out visual working memory jobs. In some trials, the visual stimulus was a slanted grating and on others it was a cloud of moving dots. Utilizing models of each cortical populations responsive field, the researchers projected the memory patterns encoded in the patterns of cortical activity onto a two-dimensional representation of visual area.
The capability to store details for quick amount of times, or “working memory,” is a building block for the majority of our greater cognitive procedures, and its dysfunction is at the heart of a range of neurologic and psychiatric symptoms, consisting of schizophrenia..
Despite its importance, we still understand extremely little about how the brain stores working memory representations..
” Although we can anticipate the contents of your working memory from the patterns of brain activity, what precisely these patterns are coding for has remained impenetrable,” Curtis states..
Curtis and co-author Yuna Kwak, an NYU doctoral student, hypothesized that our brains not only discard task-irrelevant functions however likewise re-code task-relevant features into memory formats that are both distinct and efficient from the perceptual inputs themselves..
Its been understood for years that we re-code visual details about letters and numbers into sound-based or phonological codes utilized for verbal working memory. When you see a string of digits of a phone number, you do not keep that visual info up until you end up calling the number. Rather you save the noises of the numbers (e.g., what the phone number “867-5309″ seems like as you say it in your head). This only shows that we do re-code– it does not address how the brain formats working memory representations, which was the focus of the new Neuron research study..
To explore this, the experimenters determined brain activity with functional magnetic resonance imaging (fMRI) while participants performed visual working memory jobs. In some trials, the visual stimulus was a tilted grating and on others it was a cloud of moving dots.
Regardless of the various kinds of visual stimulation (grating vs. dot movement), they discovered that the patterns of neural activity in visual cortex and parietal cortex– a part of the brain used in memory processing and storage– were interchangeable during memory. In other words, the pattern trained to anticipate motion direction could also predict grating orientation– and vice versa..
This finding triggered the question– why were those memory representations interchangeable?
” We reasoned that only the task-relevant features of the tested stimuli were drawn out and re-coded into a shared memory format, perhaps taking the kind of an abstract line-like shape angled to match either the orientation of the grating or the direction of dot motion,” discusses Curtis..
To test this hypothesis that individuals memories were tape-recorded into a line-like pattern– comparable to envisioning a line at a certain angle– they relied on a novel method to envision the patterns of brain activity..
Utilizing designs of each cortical populations receptive field, the scientists forecasted the memory patterns encoded in the patterns of cortical activity onto a two-dimensional representation of visual area. This method developed a representation of the cortical activity within the area of the display that the individuals saw. This method enabled the scientists to visualize in screen coordinates the pattern of the subjects cortical activity, exposing a line-like representation for both motion and grating stimuli.
” We might see lines of activity across the topographic maps at angles corresponding to the movement direction and grating,” explains Curtis..
This unique visualization method offered an opportunity to really “see” how working memory representations were encoded in a neural population..
Specifically, a single line (like a pointer or arrow) was used to represent the instructions of movement (e.g., up and to the left) and the orientation of a slanted grating (e.g., up and to the left). The job required subjects to remember not all the moving dots but, rather, only a summary of the dots motion direction. It needed memory for the angle of the grating, and not all the other visual details of the grating, such as spatial frequency and contrast. The approach was able to separate how we selectively save pertinent information while disposing of irrelevant content..
” Our visual memory is versatile and can be abstractions of what we see driven by the habits they assist,” Curtis concludes.
Recommendation: “Unveiling the abstract format of mnemonic representations” by Yuna Kwak and Clayton E. Curtis, 7 July 2022, Neuron.DOI: 10.1016/ j.neuron.2022.03.016.
The research study was supported by National Institutes of Health grants from the National Eye Institute (NEI) (R01 EY-016407, R01 EY-027925).