A new era driven by better memory - aiming for a richer and more creative future

LANGUAGE ≫ Japanese

TAKEDA Masaki

Specialized field: Neuroscience

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Sleep is essential for all animals to live. Getting good sleep not only maintains mental and physical health but also plays a major role in memory consolidation. While it might seem like sleeping causes us to forget what we have learned, it has been found that sleeping actually makes memories more likely to endure. Professor Masaki Takeda, who conducts integrated research on brain and nerve function, from the level of cellular units to the entire human being, is focusing on this relationship between sleep and memory and attempting to elucidate the mechanisms of memory that occur in the brain during sleep using cutting-edge technology.

Among all cognitive functions, memory is what makes humans human

The brain is one of the most mysterious organs in the human body. Many mysteries still remain about its complex and amazing workings. Professor Takeda, a neuroscientist, became aware of how the brain functions due to a simple question he had as a junior high school student.

"I had a crush on a girl, and every day my head was completely filled with thoughts of her. Among the hundreds of millions of women in the world, why did I keep thinking only about that girl? My other friends didn't think anything special about her. I started wondering where this difference in thinking comes from."

Due to this experience, he became interested in the flexibility of the brain that supports people's emotions, thoughts, and behavior, and he majored in psychology in university because he wanted to learn about "love." However, as his research progressed, he came to think that "in order to understand the human mind, it is necessary to study the brain itself," and from his master's program onward, he pursued the path of neuroscience.

While immersed in brain and nerve research, Professor Takeda says he became convinced of one thing: that "among human cognitive functions, the most important is memory." He further emphasizes that "memory is what makes humans human."

"We can remember and recall all kinds of things every day. This function called memory becomes the foundation for us to understand ourselves and form our identity."

Beyond that, memory is also a matter of particularly great interest to us among the many cognitive functions such as memory, attention, judgment, understanding, and thinking.

"For example, during our student days we think about how to memorize things efficiently before tests, and as we age we work hard at brain training to maintain our memory. Memory is deeply connected to daily life, and across generations there is a widespread shared understanding that we want to improve it. I find that aspect fascinating, and have consistently focused on memory."

Professor Takeda is working to elucidate the mechanisms of memory, focusing particularly on "semantic memory," which involves remembering knowledge and concepts used in daily life. He explains that "semantic memory is indispensable when we memorize or recall something." For example, music we happen to hear can sometimes evoke nostalgic scenes or events from childhood. At such times, information like song titles and songwriters is stored in the brain as semantic memory. In other words, semantic memory is not merely fragments of knowledge, but something that supports our rich daily memory experiences.

What is the "replay activity" that consolidates memory during sleep?

Sleep is closely related to this memory. It is known that memory is consolidated through sleep. Professor Takeda: "They say the key to this memory fixation process is the 'replay activity' that occurs during sleep." What exactly is this phenomenon?

"Replay activity is a phenomenon where the brain reproduces, while sleeping, events experienced or things learned during the day. For example, after memorizing colleagues' faces and names at a company orientation ceremony, the brain reproduces the brain activity from that time during sleep. Research with mice has confirmed that when replay activity is detected during sleep, memory performance improves after waking up."

Professor Takeda's research team aims to detect replay activity during human sleep as well and to be the first in the world to clarify how it contributes to memory consolidation. However, because brain activity during sleep is extremely complex and very noisy, accurate detection is difficult with a single measurement method. Therefore, Professor Takeda and his colleagues have developed technology that simultaneously measures brain activity by combining functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), establishing a method to record brain activity patterns more precisely. Furthermore, they are also developing high-precision analysis methods for brain activity data using deep learning.

In parallel with this, they have also focused on "sleep slow waves," which are believed to be related to replay activity. Sleep slow waves are regular waves that appear in the frontal lobe of the cerebrum during deep sleep. Professor Takeda's team hypothesized that, if these waves are involved in memory consolidation, then enhancing them should improve memory performance after waking, while weakening them should degrade performance, and they conducted experiments on that basis. To do that, Professor Takeda and colleagues independently developed a "closed-loop system" that monitors brain activity during sleep, detects sleep slow waves in real time, and delivers electrical current stimulation to the brain in accordance with their timing. Using this system, they manipulated the strength of the waves and verified what changes occurred in memory performance.

"In experiments with university students, we obtained results that matched our hypothesis: when sleep slow waves were enhanced, memory performance after waking improved, and conversely, performance declined when waves were weakened."

Replay activity is also believed to involve deep regions of the brain that electrical stimulation cannot reach. Therefore, they have also begun new experiments using ultrasound stimulation. He explains: "Ultrasound stimulation can reach deep into the brain, enabling detection of activity in deep brain regions that was previously difficult." If this research progresses, it will likely bring us significantly closer to fully understanding replay activity.

"Our strength lies in being able to conduct experiments using simultaneous measurement technology that takes advantage of our university's research environment, as well as the 'closed-loop system' we developed independently. This technology has made it possible to manipulate the strength of sleep slow waves. Furthermore, our attempts to analyze simultaneously measured brain activity data with AI are, as far as I know, the first in the world. We take pride in leading the world in research through the introduction of such cutting-edge technologies."

Toward development of future wearable devices that enhance memory

Professor Takeda's goal is to "develop devices that enhance human memory by applying research findings relating to memory."

"More specifically, I envision a device that can be attached to a pillow to automatically monitor brain waves during sleep and deliver electrical stimulation at the most effective timing. This has two purposes: one is to maintain memory in elderly people, and the other is to improve memory in children. While memory capabilities have genetic factors, they also change flexibly depending on the environment and experiences after birth. I think there are many cases where people face disadvantages in life simply because they do not have good memory, and I want to raise every child's memory to at least a certain level. By doing so, I believe perhaps we can realize a society where people can reduce the time they've previously spent on memorization and develop their individuality through creativity and imagination."

Creativity and inspiration do not come from nowhere. They are largely based on memory and experience. Improving memory should certainly help not only with learning but also with enhancing creativity and imagination.

"However, technical challenges remain in developing such devices. While development of devices based on brain waves is progressing, there are still technical limitations in developing devices that utilize data from large MRI machines. In the research world, on the other hand, an extremely large number of results have been obtained using MRI. Therefore, I want to find a mechanism for converting MRI data into brain wave data. In that way, I want to develop devices that utilize MRI data, for which there is a tremendous accumulation of research, and disseminate them throughout society. I think it will still take time, but I am confident that practical application in the future is very possible."

Professor Takeda's research has the potential to change our brain function, daily life, and society for the better. He will continue to tackle challenges going forward, aiming for a future where everyone has excellent memory and can freely exercise creativity.

Date of posting: June, 2025/ Date of interview: March, 2025