睡眠如何重組我們的記憶？

Perhaps sensing that we needed one more excuse to sleep in, scientists at Germany's Ruhr-Universität Bochum and the University of Bonn decided to investigate how catching ZZZs affects our memory. By recording brain activity, they found that certain memories could be reactivated when we sleep despite not being remembered later on.

或許我們需要給睡懶覺再找個(gè)理由。德國波鴻大學(xué)和波恩大學(xué)的科學(xué)家們決定研究睡眠如何影響記憶。通過記錄大腦活動，他們發(fā)現(xiàn)在睡眠過程中，一些記憶能夠被喚醒，盡管后來不再記得。

The study, published in the October 2018 journal of Nature Communications, details what occurred during an experiment involving epilepsy patients. Due to surgical planning, these subjects had electrodes implanted into their brains, thus making the recording of brain activity a pretty straightforward endeavor. The researchers gave the participants a series of pictures to memorize, and then allowed them all to nap. By measuring the differences in their high-frequency brain activity changes (known as gamma band activity), the scientists could analyze what was going on in the patients' brains during the learning task and while they slept.

這項(xiàng)研究發(fā)表在2018年10月的自然通訊(Nature Communications)雜志上，詳細(xì)描述了癲癇患者在實(shí)驗(yàn)過程中的情況。通過手術(shù)，將電極植入了這些受試者腦中，以此來直接記錄他們的腦部活動。研究者們在學(xué)習(xí)任務(wù)中給出一系列圖片讓受試者記住，然后讓他們?nèi)胨?，通過測量他們腦中高頻活動(伽馬波的活動)變化的不同，科學(xué)家們能夠分析出受試者在記憶圖片時(shí)和睡眠過程中腦部發(fā)生的活動。

Post-nap, the participants were tested on which images from the learning task they could remember and which they couldn't. It turned out that certain gamma band activity patterns occurred when first examining the pictures, and then again during sleep. The participants' brains were reactivating patterns during their naps, even for images they later forgot. So, according to a statement from researcher Dr. Hui Zhang, "The forgotten images do not simply disappear from the brain."

小睡過后，受試者對學(xué)習(xí)任務(wù)中的圖像進(jìn)行測試，看他們還能夠記住哪些圖像。結(jié)果顯示，部分伽馬波的活動在學(xué)習(xí)過程中發(fā)生，并在睡眠中再次發(fā)生。受試者的大腦在睡眠中會回憶起所學(xué)圖像內(nèi)容，包括后來他們在測試中已經(jīng)忘記了的。因此，Hui Zhang博士在報(bào)告中提到：“后來被忘記的圖片并未消失在腦海中。”

Just because gamma band activity was reactivated for certain images during sleep didn't mean the participants necessarily remembered those images when they woke up. The key factor for retaining the picture in wakefulness was activity in the hippocampus, the brain region that's critical for memory. Activity in this area of the brain is measured in quick changes called "ripples." When participants displayed gamma band activity and ripples in the hippocampus at the same time during certain sleep cycles, that double whammy enabled them to potentially recall the image when they were awake.

這是因?yàn)橘ゑR波的活動會在睡眠中“恢復(fù)”一些圖像，但這并不意味著受試者醒來后也會記得這些。想要在清醒時(shí)候依舊“保留”住這些圖像的關(guān)鍵因素是大腦中決定記憶的區(qū)域，即海馬體的活動。大腦中這部分區(qū)域的活動用“波紋”的變化來衡量。當(dāng)受試者在特定的睡眠周期同時(shí)發(fā)生伽馬波的活動及海馬體波紋時(shí)，這樣的雙重刺激可能會使得受試者在清醒時(shí)回憶起那些圖像。

But aside from the requisite dual gamma band/hippocampus activity, there was another important factor that ensured the participants would remember an image during wakefulness: How the details of the image were processed. Researchers distinguished between two stages of gamma band activity: Superficial processing occurred in the first half second after a participant was presented with an image, and the deep processing stage was anything after that.

但除了這“雙重刺激”外，還有一個(gè)重要因素能夠確保受試者在清醒狀態(tài)下回憶起圖像，那就是：如何處理圖像的細(xì)節(jié)。研究者們區(qū)劃分出了伽馬波活動的兩個(gè)階段：表面化的處理發(fā)生在受試者看到圖像的前半秒，深度處理階段則在此之后。

So in order for a participant to remember the image after sleep, the gamma band activity from the deep processing phase had to have been reactivated simultaneously with the ripples in the hippocampus. If all that synchronicity occurred, but the reactivated activity was from the superficial phase, participants forgot the image.

因此，為了受試者在睡眠后仍能夠記住圖像，“深度處理”階段的伽馬波活動需要同時(shí)被海馬體波紋再“激活”。即便這些都在大腦中同時(shí)發(fā)生，但是被“激活”的是表面化處理階段，受試者還是會忘記圖像的內(nèi)容。