by Our memories are rich in details: we can vividly remember the color of our house, the layout of our kitchen, or the facade of our favorite coffee shop. How the brain encodes this information has baffled researchers. neuroscientists for a long time.
Now, a study led by the Dartmouth University (USA), researchers identify a neural coding mechanism that allows information to be transferred back and forth between perceptual regions and memory areas of the brain. The results are published in ‘Nature Neuroscience‘.
Before this work, the classical understanding of brain organization was that the perceptual regions of the brain represented the world “as it is,” and that the visual cortex of the brain represented the external world based on how light hits the retina. «retinotopically«. In contrast, memory areas of the brain were thought to represent information in an abstract format, stripped of details about its physical nature. However, according to the co-authors, this explanation does not take into account that as information is encoded or remembered, these regions may, in fact, share a common code in the brain.
«We found that memory-related brain areas encode the world as a ‘photographic negative’ in space» says co-lead author Adam Steel. “And that ‘negative’ is part of the mechanics that moves information in and out of memory, and between perception and memory systems.”
In a series of experiments, participants’ perception and memory were tested while their brain activity was recorded using a functional magnetic resonance imaging (fMRI) scanner. The team identified an opposing push-pull coding mechanism, which governs the interaction between perception and memory areas in the brain.
The results show that when light reaches the retina, the visual areas of the brain respond by increasing their activity to represent the light pattern. The memory areas of the brain also respond to visual stimulation, but unlike visual areas, their neural activity decreases when they process the same visual pattern.
The co-authors report that the study has three unusual findings. The first is his discovery that a principle of visual coding is preserved in memory systems.
neurons
The second is that this visual code is backwards in memory systems. “When you see something in your visual field, neurons in the visual cortex activate while those in the memory system calm down,” explains the lead author. Carolina Robertson.
Third, this relationship changes during recall. “If you close your eyes and remember the visual stimuli in the same space, you will change the relationship: your memory system will be driving, suppressing the neurons in the perceptual regions,” says Robertson.
“Our results provide a clear example of how memory systems use shared visual information to focus and unfocus memories,” says co-senior author Ed Silson.
In the future, the team plans to explore how this push-pull dynamic between perception and memory may contribute to challenges in clinical conditions, including Alzheimer’s disease.
