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Hello everyone, SCIEN-SPOT is a podcast that shines a spotlight on the latest scientific technology from Japan.
Your host is REN from SCIEN-TALK.
作業記憶の機能
Now, in our daily lives, we unconsciously perform the act of temporarily remembering something, and then quickly forgetting it when it's no longer needed.
For instance, when you're talking with a friend, you temporarily hold what they said in your mind to formulate an appropriate response.
Or, when you're cooking and juggling multiple tasks, you remember the current step and then efficiently clear it from your mind when you move on to the next task.
This ability to temporarily hold information, use it as needed, and remove unnecessary information is technically called working memory.
It's a fundamental function, serving as the basis for our thoughts and flexible behavior.
The command center for this working memory is located in the frontal lobe of our brain.
The frontal lobe, a large area situated just behind your forehead, is responsible for higher-level brain functions such as thinking, judging, and behavioral control.
However, what happens if this updating or erasing of short-term memory doesn't work correctly?
For example, information that enters your mind might persist, making it difficult for new information to be processed.
Or, you might struggle to switch between thoughts or actions, leading to a lack of flexible responses.
In fact, it's known that many mental and developmental disorders, such as schizophrenia, aggressive compulsive disorder, and autism spectrum disorder, exhibit these qualities with such memory manipulation.
Until now, the process mechanisms by which information is updated or erased in the brain remained largely unknown.
Now we're sharing news about a significant discovery made by a research group led by Assistant Professor Ryu Sawagashira and Professor Masaaki Tanaka from Hokkaido University Graduate School of Medicine, who have tackled this long-standing mystery.
In their research, they conducted experiments using monkeys.
They trained the monkeys to perform a modified version of the N-Bug task.
This is a widely used psychological test.
短期記憶の評価
In this task, visual stimuli like dots appear sequentially on the screen.
The monkeys had to remember their position in order and, upon the signal, make eye movements to the position of the stimulus presented one or two steps earlier.
This task allowed them to quantitatively assess the monkeys' cognitive operations, including the retention, updating, and erasure of short-term memory.
The research team recorded neural activity at the single-cell levels in a specific region of the monkeys' frontal lobe.
Specifically, the prefrontal cortex, while they performed this task.
The prefrontal cortex is a seat of working memory.
As a result, they made an astonishing discovery.
They found two distinct types of neurons.
One type is a neural cell that remains active while we temporarily hold specific information in our minds, meaning it's active during memory retention.
These were named memory neurons.
You can think of this as information being written on a temporary notepad in our minds.
And now, for the highlight of this research, they discovered a new type of neurons that becomes transiently active when the specific memory of a stimulus position is no longer needed.
That is, when it has served its purpose.
消去ニューロンの発見
These neurons have been named extinction neurons.
The activity of these extinction neurons is thought to function almost like erasing a news memo from your head.
What's more, when weak electrical stimulation was applied to the recorded neural site at the exact moment these extinction neurons were active,
the monkeys exhibited behavior as if only the memory of a specific stimulus position had been erased from their brains.
This provides scientific evidence that extinction neurons truly play a crucial role in the ensure of short-time memory and flexible information switching.
Machine learning analysis was built with just these neurons.
They could predict the monkeys' behavior with 90% accuracy.
This indicates how efficiently and centrally these neurons contribute to our memory manipulation.
This discovery has shed light on the fundamental mechanism of the brain,
how we remember information and how we forget it when necessary.
It is particularly expected to significantly contribute to clarifying the pathology of mental illness where not only is memory itself impaired,
but also the ability to flex and manipulate, select and manage memories is compromised.
Looking forward, this research suggests the potential for developing new non-pharmacological therapies,
such as brain stimulation or neural modulation techniques, which could specifically target the function of these extinction neurons.
This could offer great help for patients who struggle with excessive memory fixation or difficulty in switching thoughts.
That's all for today's SciencePod.
This podcast is broadcast daily or weekday morning in both Japanese and English.
I hope today's discovery has changed how you view your memory, even just a little.
I'd love for you to listen to the podcast and positive notes and thoughts with the hashtag SciencePod.
See you next time.
