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    Home > Active Ingredient News > Study of Nervous System > Science: Challenge classics, artificial hallucinations, scientists reveal the neural mechanism of dopamine-induced hallucinations

    Science: Challenge classics, artificial hallucinations, scientists reveal the neural mechanism of dopamine-induced hallucinations

    • Last Update: 2021-04-19
    • Source: Internet
    • Author: User
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    We still remember that during the internship at the Mental Health Center, the teacher introduced a schizophrenic patient and asked him to complain about his illness.
    He talked a lot and said with great emotion that he has a special function.
    Can hear what others can't hear, see what others can't see, and point to the corner while talking, vowing to say that something is buried underground.

    Really, I believe it, because what he said is the same as the real thing.

    Later, the teacher said that during the onset of psychosis, patients may obtain false beliefs, or believe with high confidence that what they see or hear is not happening.
    This is an illusion.

    In fact, in many cases, normal people will have hallucinations after many psychological cues.

    An illusion is a false perception.
    It has the same subjective confidence as the real perception, and it has a feeling like it is true.

    But animals cannot express their experiences intuitively, so researchers can only evaluate indirect responses such as drug-induced motion or pre-pulse inhibition of startle reflexes.

    On April 2, 2021, the research team of K.
    Schmack and Sturgill, A.
    Kepecs of Cold Spring Harbor Laboratory published an article in the journal Science to challenge the classics, fully replicate human hallucinations in mice, and reveal that striatal dopamine regulates this An illusion.

    Mice perform auditory hallucination experiments.
    Researchers divide the mice into a non-signal group and a signal group.
    The whole experiment is divided into four stages.

    In the detect period, the two groups always play background signal noise, and the signal group plays different tones of sound signals (35 dB-65 dB).

    Then enter the choose period, the mouse can touch the buttons through the nose, a right button, and a left button.

    The signal indicator of the button remains unchanged in the no signal group, and changes with the size of the sound decibel in the signal group.

    No matter which button is selected, it will enter the Investment period.
    After selecting one of the buttons (such as the right button) in the no signal group, it will be counted as correct reject, and after selecting the left button, it will be False Alarm.
    In the signal group, the mouse will select the right button It is counted as hit group, and selecting the left button is counted as miss group.

    In the reward period, only hit and correct reject mice will receive food and water rewards.

    After a period of training, the accuracy rate of the mice to complete the task correctly increased significantly.

    But in all the testing process, the proportion of the sound signal still heard in the no signal group is 16%, which is relatively high.

    Before entering the reward period, the mice have 0.
    5-5 seconds "consider decision" time in the Investment period, and the shortness of this decision time can be used to measure their confidence in hearing the sound.

    The longer the False Alarm mouse takes to make decisions during this period, the more confident it is in its own wrong perception.
    This high confidence in wrong consciousness is called hallucinations.

    Humans conduct auditory hallucination experiments.
    Researchers have conducted similar experiments on humans, and the same can show hallucinations.

    It's just different from animal experiments.
    In the investment period, humans indicate their confidence level by sliding the scale on the ruler (the more the scale goes to the right, the more confident it is).

    Ketamine can cause mental abnormalities in humans-visual and auditory distortions.

    The researchers found that the proportion of False Alarm mice was significantly increased after ketamine injection before the above experiment, and the time for False Alarm mice to make decisions during the Investment period was also prolonged.
    This indicates that ketamine induces hallucinations in mice as in humans.

    This indicates that the hallucinations that exist in humans have been successfully replicated in mice.

    Dopamine has always been considered to play a key role in the occurrence of hallucinations.

    Hallucinations can be treated with antipsychotic drugs that block dopamine.

    The ventral striatum (VS) is mainly responsible for the coding of reward information, while the dorsal caudal part of the striatum (TS) is mainly responsible for the coding of perceptual information.

    Fiber-optic recording of dopamine concentration changes in striatal subregions in vivo.
    Researchers injected AAV viruses expressing dopamine fluorescent probes into the VS and TS brain regions respectively.
    Then, through the fiber-optic calcium imaging technology system, they found that before the mouse has hallucinations, the above two The concentration of dopamine in each brain area increases.

    Through optogenetic technology to specifically promote the release of dopamine in the TS brain area, it can induce hallucinations in mice: it enhances the confidence of False Alarm mice.

    Dopamine receptor antagonists can block hallucinations caused by light activation.

    In general, this article solves the limitation that mice cannot express their own ideas subjectively.
    Through designing ingenious experiments, it can completely replicate human hallucination perceptions in mice, and further reveals that dopamine regulates the dopamine in the dorsal tail of the striatum.
    An illusion.

    [References] 1.
    https://doi.
    org/10.
    1126/science.
    abf4740 The pictures in the article are all from the references
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