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    Home > Biochemistry News > Biotechnology News > The "memory center" of the brain needs to recognize a series of images, not a single image

    The "memory center" of the brain needs to recognize a series of images, not a single image

    • Last Update: 2021-07-30
    • Source: Internet
    • Author: User
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    A new study by the Massachusetts Institute of Technology, the mammalian brain remembers the display it sees.
    Although individual images are stored in the visual cortex, the ability to recognize landscape sequences is extremely dependent on the guidance of the hippocampus.
    A deeper structure is closely related to memory but shrouded in it.
    Mystery to the end

    .

    A new study published in the journal Current Biology shows that in basic image storage, the hippocampus is not needed to identify possible temporal relationships between images
    .
    This research can give neuroscientists a deeper understanding of how the brain coordinates long-term visual memory in key areas

    .

    Mark Bell, Professor of Neuroscience and senior author at the Picall Institute of Learning and Memory and the Department of Brain and Cognitive Sciences at MIT, said: “This provides an opportunity to come in a very specific way.
    Really understand how the hippocampus promotes memory storage in the cerebral cortex

    .
    "

    Peter Finnie, a former postdoctoral fellow at Bell Labs, said that essentially, the hippocampus affects the way images are stored in the cerebral cortex, if there is a sequential relationship between the images
    .

    Finney said: "The exciting thing is that the visual cortex seems to be involved in encoding very simple visual stimuli and their time series, and the hippocampus is selectively involved in how these sequences are stored
    .
    "

    Hippocampus but not

    To realize their discovery, researchers including former postdoc Rob Komorowski used two forms of visual recognition memory discovered by Bell Labs to train mice
    .
    The first form of memory is called stimulus selective response plasticity (SRP), and it involves learning to recognize a single non-reward, non-threatening visual stimulus after it has been repeatedly presented

    .
    As learning takes place, neurons in the visual cortex produce more and more intense electrical responses, and mice no longer pay attention to images that were once novel but are now uninteresting

    .
    The second form of memory, visual sequence plasticity, involves learning to recognize and predict a series of images

    .
    Here, the same, once novel but now familiar and harmless sequence elicits an increased electrical response that is much greater than that observed when the same stimulus is presented in the reverse order or at a different speed

    .

    In previous research, Bell's laboratory has shown that images of each memory form are stored in the visual cortex.
    If only one eye sees these images, then they are even specific to which eye sees them

    .

    But researchers are curious about whether and how the hippocampus promotes these forms of memory and cortical plasticity
    .
    After all, just like some other forms of memory that rely on the hippocampus, SRP only forms after a period of "consolidation", such as when sleeping at night

    .
    To test whether the hippocampus works, they chemically removed most of the structure of the hippocampus in a group of mice, and looked for differences between different groups in the electrical response caused by each recognition memory

    .

    Mice with or without the hippocampus performed equally well in learning SRP (not only an electrophysiological measurement, but also a behavioral measurement), indicating that the hippocampus does not need this form of memory
    .
    It seems to appear entirely within the visual cortex, and even consolidate

    .

    However, the researchers found that if the hippocampus is incomplete, visual sequence plasticity does not occur
    .
    In the test, mice without this structure showed no elevated electrical response to these sequences, and were unable to reversely recognize or delay recognition of them, and when one of the sequences was missing, there was no tendency to "fill in the blank"

    .
    It seems that the visual sequence—even every image in the sequence—is unfamiliar

    .

    The author writes: "In general, these findings are consistent with the specific role of the hippocampus in predicting response generation when exposed to familiar transient visual stimuli
    .
    "

    New discoveries in classic methods

    These experiments follow the long-standing tradition of trying to understand the hippocampus by assessing what happens when the hippocampus is damaged
    .
    For decades, neuroscientists at the Massachusetts Institute of Technology (MIT) and elsewhere have been able to learn from a man named "hm" who underwent hippocampal removal surgery to relieve seizures

    .
    His memory of the past before the operation was still intact, but he showed that he was unable to form "declarative" memories of new experiences, such as meeting someone or performing an activity

    .
    However, over time, scientists realized that he could learn motor tasks better through training, even if he did not remember the training itself

    .
    These experiments help to reveal that for many different forms of memory, there is a "division of labor" between various areas of the brain, which may or may not include the hippocampus

    .

    Bell and Finney say that this new study uses the division of visual memory to create a clear distinction between simple image recognition and more complex sequence structure recognition tasks
    .

    "This is a good dividing line," Bell said
    .
    "This is the same area of ​​the brain, the same way that animals look at images on the screen

    .
    All we change is the time structure of the stimulus

    .
    "

    Alzheimer's disease assessment?

    Previous laboratory studies have shown that SRP and visual sequence plasticity are produced through different molecular mechanisms
    .
    SRP can be destroyed by blocking the neurotransmitter glutamate receptors involved in neurons, and sequence plasticity depends on acetylcholine receptors

    .

    Therefore, the next question that Bell wants to solve is whether there is a circuit that produces acetylcholine to connect the hippocampus and the visual cortex to complete sequential learning
    .
    The neurons that release acetylcholine in the cerebral cortex happen to be one of the first neurons to be destroyed in Alzheimer's disease

    .

    Bell speculates that if the circuit of sequence learning does run through these neurons, then assessing people's differences in SRP and sequence learning may become a way to diagnose the progression of early dementia
    .

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