Neuroscience used to be confident that the brain produced memory and perception in different ways. In the 1990s, research showed that parts of the brain that were thought to be inactive only during sensory perception are active during the recall of memories.
Sam Ling is an associate professor of neuroscience and director of the visual neuroscience lab at Boston University. Is it possible that our memory of a beautiful forest glade is just a re-creation of the neural activity that allowed us to see it?
Christopher Baker is an investigator at the National Institute of Mental Health who runs the learning and plasticity unit. The pendulum swung from one side to the other.
We know that memories and experiences can't be the same, even if there is a strong similarity. Serra Favila is the lead author of a recent Nature Communications study. At least one of the ways in which memories and perception of images are different at the neurological level has been identified by her team.
When we look at the world, visual information is sent from the back of the eye to the front of the brain. Each group adds new levels of complexity to the image: simple dots of light turn into lines and edges, then shapes, then complete scenes that embody what we're seeing.
The question of whether a memory representation is different from a perceptual representation began to be raised.
Sam Ling is a student at Boston University.
In the new study, the researchers focused on a feature of vision processing that is very important in the early groups of neuron. The brain will create a distorted image if the images are not in the correct places.
Participants were trained to memorize four different patterns on a backdrop that looked like a dart board. Each pattern was associated with a color at the center of the board. The participants were tested to make sure they knew the star shape was at the far left position if they saw a green dot. The researchers recorded the participants' brain activity when they remembered the patterns.
Researchers were able to map out how the brain scans recorded where and how they remembered it with the help of the scans. There is a receptive field in the lower left corner of your vision. Favila said that a neuron only fires when something is placed in it. It's easy to detect activity in brain scans if there's a cluster of them.
There are small receptive fields in the early levels of processing and larger ones in later levels. It makes sense because the higher-tier neurons are drawing in signals from the lower-tier ones. The bigger receptive field creates an effect like putting a large blob of ink over North America on a map to indicate New Jersey It's a matter of small dots evolving into larger, blurrier but more meaningful blobs.
Major differences were discovered when Favila and her colleagues looked at how perception and memories were represented.
The receptive fields in the highest level of visual processing were the same size as they had been during perception, but the receptive fields stayed that size down through all the other levels. There was a blurry blob at every stage.
The highest level representation of the image was kept when the memory was stored. The parts of the visual cortex that were activated when the memory was experienced again were based on the less precise version of the memory.
The brain processes information in different ways depending on where it comes from and what it is. Favila said that it was not possible to get the original perception back.
The researchers were able to read out the information from the brain instead of relying on the human subject to report what they saw. The empirical work that they did is really good.
There is a question as to why memories are recalled in this way. The researchers created a model of the visual cortex that had different levels of neural activity. In reverse order, they sent a signal through the levels. The spatial blurriness seen in the level with the largest receptive field persisted through all the other levels. It's possible that the remembered image forms in this way because of the hierarchy of the visual system.
The visual system is arranged in a way that makes it easier to recognize objects. Favila said that if receptive fields were small, the brain would need to integrate more information to make sense of what it was seeing. Theblurrier memory image might be the result of having a system that has been improved for object recognition.
Thomas Naselaris is an associate professor at the University of Minnesota. He came to the same conclusion that he did when he was not involved in the new study. The idea that the difference is beneficial is something he supports. He said that a person with all of the detail and precision of their scene imagery could get confused.
Storage of unneeded information could be prevented by the blurriness. Favila said that the important thing isn't to remember where each person sits in the field of vision, but that they are a family member or a friend.
The visual system is capable of generating highly detailed, vivid and precise images. People have reported seeing very vivid images when they are in the state of hypnogogic. The brain doesn't tend to do it during the day.
Favila and her team want to find out if similar processing can happen with other aspects of a visual memory. They want to understand how perception and memory guide behavior.
It is important to understand how memory is expressed by pinning down the ways in which perception and memory are different. The differences kept showing up in the data.
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