睡眠如何重组我们的记忆？

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.

或许我们需要给睡懒觉再找个理由。德国波鸿大学和波恩大学的科学家们决定研究睡眠如何影响记忆。通过记录大脑活动，他们发现在睡眠过程中，一些记忆能够被唤醒，尽管后来不再记得。

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.

这项研究发表在2018年10月的自然通讯(Nature Communications)杂志上，详细描述了癫痫患者在实验过程中的情况。通过手术，将电极植入了这些受试者脑中，以此来直接记录他们的脑部活动。研究者们在学习任务中给出一系列图片让受试者记住，然后让他们入睡，通过测量他们脑中高频活动(伽马波的活动)变化的不同，科学家们能够分析出受试者在记忆图片时和睡眠过程中脑部发生的活动。

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."

小睡过后，受试者对学习任务中的图像进行测试，看他们还能够记住哪些图像。结果显示，部分伽马波的活动在学习过程中发生，并在睡眠中再次发生。受试者的大脑在睡眠中会回忆起所学图像内容，包括后来他们在测试中已经忘记了的。因此，Hui Zhang博士在报告中提到：“后来被忘记的图片并未消失在脑海中。”

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.

这是因为伽马波的活动会在睡眠中“恢复”一些图像，但这并不意味着受试者醒来后也会记得这些。想要在清醒时候依旧“保留”住这些图像的关键因素是大脑中决定记忆的区域，即海马体的活动。大脑中这部分区域的活动用“波纹”的变化来衡量。当受试者在特定的睡眠周期同时发生伽马波的活动及海马体波纹时，这样的双重刺激可能会使得受试者在清醒时回忆起那些图像。

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.

但除了这“双重刺激”外，还有一个重要因素能够确保受试者在清醒状态下回忆起图像，那就是：如何处理图像的细节。研究者们区划分出了伽马波活动的两个阶段：表面化的处理发生在受试者看到图像的前半秒，深度处理阶段则在此之后。

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，为了受试者在睡眠后仍能够记住图像，“深度处理”阶段的伽马波活动需要同时被海马体波纹再“激活”。即便这些都在大脑中同时发生，但是被“激活”的是表面化处理阶段，受试者还是会忘记图像的内容。