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April 22, 2016

どのようにトラウマ記憶は、脳内に隠れ、どのようにしてそれを取り出すか。Science daily より

How traumatic memories hide in the brain, and how to retrieve them

どのようにトラウマ記憶は、脳内に隠れ、どのようにしてそれを取り出すか。Science daily より

traumatic memories トラウマ記憶

Special brain mechanism discovered to store stress-related, unconscious memories


Some stressful experiences -- such as chronic childhood abuse -- are so overwhelming and traumatic, the memories hide like a shadow in the brain.


childhood abuse 児童虐待

At first, hidden memories that can't be consciously accessed may protect the individual from the emotional pain of recalling the event. But eventually those suppressed memories can cause debilitating psychological problems, such as anxiety, depression, post-traumatic stress disorder or dissociative disorders.


hidden memories 隠された記憶
suppressed memories 抑圧された記憶
post-traumatic stress disorder心的外傷後ストレス障害
dissociative disorders.解離性障害
psychological problems 心理的問題

A process known as state-dependent learning is believed to contribute to the formation of memories that are inaccessible to normal consciousness. Thus, memories formed in a particular mood, arousal or drug-induced state can best be retrieved when the brain is back in that state.


state-dependent learning  状態依存性学習
normal consciousness.通常の意識

In a new study with mice, Northwestern Medicine scientists have discovered for the first time the mechanism by which state-dependent learning renders stressful fear-related memories consciously inaccessible.

"The findings show there are multiple pathways to storage of fear-inducing memories, and we identified an important one for fear-related memories," said principal investigator Dr. Jelena Radulovic, the Dunbar Professor in Bipolar Disease at Northwestern University Feinberg School of Medicine. "This could eventually lead to new treatments for patients with psychiatric disorders for whom conscious access to their traumatic memories is needed if they are to recover."

「研究結果は、恐怖を誘発する記憶を保持するための複数経路が存在することを示し、私たちは恐怖関連した記憶に対する重要なひとつのものを特定したと、ノースウェスタン大学、Feinberg School of Medicine、の主任研究員のDr. Jelena Radulovic, the Dunbar Professorは述べた。「これは、彼らが回復する場合には、最終的にトラウマ記憶に意識的にアクセスする必要としている精神疾患患者に対する新たな治療法につながる可能性があります。」

fear-inducing memories 恐怖誘発する記憶
Bipolar Disease 双極性障害
psychiatric disorders  精神疾患

It's difficult for therapists to help these patients, Radulovic said, because the patients themselves can't remember their traumatic experiences that are the root cause of their symptoms.


The best way to access the memories in this system is to return the brain to the same state of consciousness as when the memory was encoded, the study showed.The study will be published August 17 in Nature Neuroscience.


Changing the Brain's Radio Frequencies


Two amino acids, glutamate and GABA, are the yin and yang of the brain, directing its emotional tides and controlling whether nerve cells are excited or inhibited (calm). Under normal conditions the system is balanced. But when we are hyper-aroused and vigilant, glutamate surges. Glutamate is also the primary chemical that helps store memories in our neuronal networks in a way that they are easy to remember.


Radio Frequencies :高周波、
glutamate グルタミン酸

GABA, on the other hand, calms us and helps us sleep, blocking the action of the excitable glutamate. The most commonly used tranquilizing drug, benzodiazepine, activates GABA receptors in our brains.


tranquilizing drug 精神安定剤
benzodiazepine ベンゾジアゼピン

There are two kinds of GABA receptors. One kind, synaptic GABA receptors, works in tandem with glutamate receptors to balance the excitation of the brain in response to external events such as stress.


glutamate receptorグルタミン酸受容体

The other population, extra-synaptic GABA receptors, are independent agents. They ignore the peppy glutamate. Instead, their job is internally focused, adjusting brain waves and mental states according to the levels of internal chemicals, such as GABA, sex hormones and micro RNAs.Extra-synaptic GABA receptors change the brain's state to make us aroused, sleepy, alert, sedated, inebriated or even psychotic. However, Northwestern scientists discovered another critical role; these receptors also help encode memories of a fear-inducing event and then store them away, hidden from consciousness.

他の個体群、シナプス領域外GABAA 受容体は独立した媒介物です。それらは活発なグルタミン酸を無視します。代わりに、それらの働きは内部に焦点を当てていて、GABA、性ホルモン、およびマイクロRNAなどの内部の化学物資濃度に応じて、脳波および精神状態を調節します。シナプス領域外GABAA 受容体は、私たちを覚醒、眠気、

extrasynaptic GABAA receptors シナプス領域外GABAA 受容体

"The brain functions in different states, much like a radio operates at AM and FM frequency bands," Radulovic said. "It's as if the brain is normally tuned to FM stations to access memories, but needs to be tuned to AM stations to access subconscious memories.If a traumatic event occurs when these extra-synaptic GABA receptors are activated, the memory of this event cannot be accessed unless these receptors are activated once again, essentially tuning the brain into the AM stations."

「ラジオはAMとFMの周波数帯域で動作すると同じように、異なる状態において脳は機能します」と、Radulovicは述べた。脳は通常記憶にアクセスするためにFM局にチューニングされているかのようだが、潜在意識の記憶にアクセスするためにAM局にチューニングする必要があります。これらのシナプス領域外GABAA 受容体が活性化すると、トラウマの出来事が発生するならば、これらの受容体が、特に脳をAM局にチューニング、再度活性化されない限り、このトラウマ記憶にアクセスすることが出来ないです。」

subconscious memories 潜在意識の記憶

Retrieving Stressful Memories in Mice


In the experiment, scientists infused the hippocampus of mice with gaboxadol, a drug that stimulates extra-synaptic GABA receptors. "It's like we got them a little inebriated, just enough to change their brain state," Radulovic said.

実験では、科学者たちは、シナプス領域外GABAA 受容体を刺激する薬剤、ガボキサドールをマウスの海馬に注入した。「それは、私たちがマウスを少し酔ったようにしたようで、マウスの脳状態を変化させるに十分だ」とRadulovicは述べた。

gaboxadol ガボキサドール(不眠治療薬)

Then the mice were put in a box and given a brief, mild electric shock. When the mice were returned to the same box the next day, they moved about freely and weren't afraid, indicating they didn't recall the earlier shock in the space. However, when scientists put the mice back on the drug and returned them to the box, they froze, fearfully anticipating another shock.


"This establishes when the mice were returned to the same brain state created by the drug, they remembered the stressful experience of the shock," Radulovic said.


The experiment showed when the extra-synaptic GABA receptors were activated with the drug, they changed the way the stressful event was encoded. In the drug-induced state, the brain used completely different molecular pathways and neuronal circuits to store the memory.

シナプス領域外GABAA 受容体が薬剤で活性化されたときに、彼らはストレスの多い出来事がコードかされた方法を変化させたことを実験は示した。薬剤誘発状態では、脳は記憶を保存するために完全に異なる分子経路と神経回路を使用した。

"It's an entirely different system even at the genetic and molecular level than the one that encodes normal memories," said lead study author Vladimir Jovasevic, who worked on the study when he was a postdoctoral fellow in Radulovic's lab.

「それは、通常記憶をコードかするものより遺伝子および分子レベルでさえ全く異なったシステムであると」、彼がRadulovic's 研究所の博士研究員であった時に研究に取り組んだ研究著者Vladimir Jovasevic,は述べた。

postdoctoral fellow 博士研究員

This different system is regulated by a small microRNA, miR-33, and may be the brain's protective mechanism when an experience is overwhelmingly stressful.
この異なるシステムは小さなマイクロRNA,  miR-33,によって調節されて、経験が圧倒的にストレスの多いときに脳の防御機構になる可能性があります。

The findings imply that in response to traumatic stress, some individuals, instead of activating the glutamate system to store memories, activate the extra-synaptic GABA system and form inaccessible traumatic memories.

この研究結果は、トラウマストレスに応答して、記憶を保存するためにグルタミン酸系を活性化する代わりに、一部の個体は、シナプス領域外GABAA 受容体を活性化して、アクセスできないトラウマ記憶を形成することを意味します。

Traumatic Memories Rerouted and Hidden Away


Memories are usually stored in distributed brain networks including the cortex, and can thus be readily accessed to consciously remember an event. But when the mice were in a different brain state induced by gaboxadol, the stressful event primarily activated subcortical memory regions of the brain. The drug rerouted the processing of stress-related memories within the brain circuits so that they couldn't be consciously accessed.


subcortical 皮質下

A process known as state-dependent learning is believed to contribute to the formation of memories that are inaccessible to normal consciousness. Thus, memories formed in a particular mood, arousal or drug-induced state can best be retrieved when the brain is back in that state.



心的外傷後ストレス障害(しんてきがいしょうごストレスしょうがい、Posttraumatic stress disorder、PTSD)は、命の安全が脅かすような出来事、天災、事故、犯罪、虐待などによって強い精神的衝撃を受けることが原因で、著しい苦痛や、生活機能の障害をもたらしているストレス障害である[1]。

シナプス領域外GABAA 受容体
理化学研究所 脳科学総合研究センター





リアノン先生主催Botanica2016, University of Sussex, Brighton, England, September 2nd - 5th 2016



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