Тархины идэвхтэй үйл ажиллагаа нь зүүдний үеэр түлшний хангамж нэмэгдэж байгаа хэдий ч мэдрэлийн эсүүдийн энергийн нөөц буурдаг болохыг эрдэмтэд тогтоожээ.
Тохоку их сургуулийн судлаачид REM буюу нүдний хурдан хөдөлгөөнтэй нойрны үед тархины эрчим хүчний зарцуулалт хэрхэн өөрчлөгддөгийг судлах зорилгоор хулганы тархийг бодит цаг хугацаанд ажиглажээ. Тэд хэт ягаан туяанд тэсвэртэй давирхай ашиглан хулганы гавлын ясыг тунгалаг болгосноор тархины цусан хангамж болон мэдрэлийн эсүүдийн ATP буюу энерги дамжуулагч молекулын түвшинг хэмжсэн байна.
Судалгааны үр дүнд REM нойр эхлэхээс 50 секундын өмнө тархины цусан хангамж нэмэгдэж, бодисын солилцооны бэлтгэл үе эхэлдэг болохыг илрүүлжээ. REM нойрны үед астроцит эсүүд дэх пируватын түвшин өсөж буй нь энергийн хангамж нэмэгдэж байгааг илтгэж байв. Гэсэн хэдий ч энэ үед мэдрэлийн эсүүдийн ATP-ийн хэмжээ эсрэгээрээ буурч байгаа нь ажиглагдсан байна.
Эрдэмтдийн таамаглаж буйгаар, энэхүү энергийн дутагдал нь зүүдлэх үед явагддаг ой санамжийг боловсруулах, синапсын бүтцийн өөрчлөлт болон тархины бүсүүдийн хоорондох мэдээлэл солилцоотой холбоотой байж болзошгүй юм. Энэхүү үзэгдэл нь биологийн оюун ухаан хэрхэн үр ашигтай ажилладаг, тархи өөрийн хязгаарлагдмал нөөцийг дотоод хэрэгцээндээ нийцүүлэн хэрхэн дахин хуваарилдаг талаар шинэ ойлголтыг өгч байна.
Communications Biology сэтгүүлд нийтлэгдсэн энэхүү судалгаа нь нойр нь зөвхөн бие махбодод бус, тархины үйл ажиллагаанд ямар чухал үүрэгтэйг тайлбарлах нэгэн чухал алхам боллоо. Хэдийгээр ATP яагаад буурч байгаагийн нарийн механизмыг бүрэн тодорхойлоогүй байгаа ч, зүүдний үеийн тархи нь эрчим хүчний өндөр эрэлттэй нөхцөлд ажилладаг гэдгийг уг судалгаа харуулж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
The brain uses an extraordinary amount of energy compared with most other organs. Even so, it can continue processing information when energy is limited by adjusting how available resources are used. Scientists are still trying to understand how the brain manages this energy budget as it moves through different internal states.
Sleep offers a useful way to study that question. Although the body is resting, the brain remains active, especially during rapid eye movement (REM) sleep, which is closely associated with dreaming and memory processing. REM sleep is often described as “paradoxical sleep” because the body is mostly still while brain activity resembles wakefulness.
Researchers at Tohoku University have now identified another REM sleep paradox. During this stage, the apparent energy supply to the dreaming brain increases, yet levels of the energy molecule neurons directly use actually decline.
The findings were published in Communications Biology.
“Ever felt exhausted after a vivid dream?” asks Professor Ko Matsui of Tohoku University. “Sleep may appear peaceful, but the brain is highly active — especially when dreaming. We were intrigued by this paradox, and wanted to look into the scientific basis behind why dreaming is somehow tiring.”
Watching the Sleeping Brain in Real Time
To investigate what happens to brain energy during sleep, the researchers used a UV-curable resin to keep the skulls of mice transparent, allowing them to observe the brain during natural sleep.
Using wide-field fluorescence imaging, they tracked changes in brain blood volume as a sign of incoming “fuel” supply. They also measured neuronal ATP, the energy molecule that powers neurons, along with astrocytic pyruvate, a key compound that connects glucose from the blood with energy metabolism in the brain.
Non-REM sleep is well known for strong neuronal activity in the delta-band frequency, but smaller theta-band fluctuations also occur. The researchers found that these theta-band changes could predict shifts in brain blood volume several seconds later. That pattern suggests the sleeping brain adjusts its blood vessels in response to changing neuronal activity and metabolic demand.
The Brain Prepares for REM Sleep in Advance
A different pattern appeared as the brain moved from non-REM sleep into REM sleep.
About 50 seconds before the classically defined beginning of REM sleep, brain blood volume started to increase. The change began in the posterior cortex and then moved forward, pointing to a large-scale process that may prepare the brain metabolically for REM sleep.
Once REM sleep began, astrocytic pyruvate also rose. That increase was consistent with either greater availability of metabolic fuel or increased glycolytic activity in astrocytes.
But at the same time, neuronal ATP fell.
Why Does Neuronal Energy Drop During Dreams?
There are several possible explanations for this decrease in ATP.
Neurons may use large amounts of ATP during REM sleep to support memory-related synaptic reorganization, communication between the hippocampus and cortex, or broad transitions across brain circuits.
Another possibility is that the transfer of metabolic resources from astrocytes to neurons changes during REM sleep. Mitochondrial production of ATP could also shift during this stage.
Whatever the mechanism, the findings suggest that the dreaming brain may be operating under unusually high energy demands even while its fuel supply increases.
A Broader Lesson About the Brain’s Energy Economy
The results may also reveal something more fundamental about biological computation.
Unlike conventional computers, animal brains must operate within strict metabolic limits. Rather than supplying energy evenly across the brain, the nervous system may redirect resources depending on behavioral state, memory demands, and other internal needs.
“Understanding how the brain balances energy supply and consumption may help explain what makes biological intelligence so efficient,” explains lead investigator Yusuke Takahashi. “REM sleep gives us a natural example of how the brain reorganizes its energy economy to support complex internal processing.”
Sleep plays a critical role in functions such as memory consolidation and maintaining mental performance the following day. By revealing how energy supply and energy use shift during REM sleep, the research adds another piece to the puzzle of why sleep is so important not only for the body, but also for the brain.
