幼兒記憶或被喚醒
你最初的記憶是在什么時候?你永遠不會擁有嬰兒時期的記憶——大多數人最早的記憶都是在三四歲開始。
But why can we not remember our infant memories? And are they really lost, or just forgotten?
但為什么我們記不起自己的嬰兒時期了呢?它們真的丟失了，還是只是被遺忘在某處角落里?
A team of neuroscientists from the University of Toronto set out to investigate, using mice to identify when and how brains forget these memories.
來自多倫多大學的神經科學家團隊就此展開了調查。他們用老鼠來設計實驗，希望追蹤到早期記憶的遺忘過程。
"Rapid forgetting has been attributed to the fact that children lack the cognitive tools to successfully consolidate and organise autobiographical memories at this early developmental stage," the team writes in the study.
他們在研究中寫道，“人們猜測，早期記憶被快速遺忘的原因是，兒童缺乏鞏固和組織自我記憶的認知工具。”
"However, similar accelerated forgetting in infancy is also observed in non-human species, including mice, suggesting that a complete neurobiological account cannot be limited to purely human phenomena."
“然而，在包括小鼠在內的非人類物種中也觀察到類似的嬰兒期遺忘現象，這就表明現象背后存在著完整的神經生物學機理。”
The researchers trained infant mice to associate a particular box with a small zap to the foot. The mice lost memory of this zap within 15 days, which is nearly analogous to humans forgetting memories of their infancy at around seven years old.
研究人員訓練新生小鼠將一個特定的盒子與對其足部的擊打聯(lián)系起來。老鼠在15天內就失去了對擊打的記憶，這幾乎相當于于人類在7歲左右忘記了嬰兒期的記憶。
The researchers then took a new set of infant mice and tagged the specific neurons active in the hippocampus when they were placed in the box and had their foot lightly zapped.
研究人員隨后換了一組新的幼鼠，并在訓練中，找到它們海馬體內活動的神經元并標記出來。
Weeks afterwards, when the memory should have been forgotten, the researchers stimulated the tagged neurons using a precise method called optogenetics, and found the mice behaved as if they recognised the box once more.
幾周之后，當記憶被遺忘時，研究人員使用光遺傳學技術精確地刺激標記處的神經元，他們發(fā)現老鼠的表現行為就好像他們再次識別了這個盒子一樣。
"The memory recall was remarkable," says senior author Paul Frankland, a neurobiologist from the SickKids Research Institute, and the University of Toronto.
“可被召回的記憶非常引人注目。”資深作者Paul Frankland說，他是兒童病理醫(yī)學研究所和多倫多大學的神經生物學家。
"These results suggest our earliest experiences are not completely forgotten or erased from the brain. Instead, we can bring them back through direct stimulation."
“這些結果表明，我們最早的人生經歷并沒有完全被大腦遺忘或清除。相反，我們可以通過直接的刺激將它們帶回來。”
The recall wasn't perfect, though. Only about 70 percent of the mice appeared to recognise the box in the following 15-90 days, and the researchers think this is partly to do with incomplete memory recovery.
但召回手段并不完美。在接下來的15-90天內，只有約70%的小鼠能夠再次識別出這個盒子，研究人員認為這與記憶恢復不完全有關。
"What we're doing by stimulating the collection of neurons, which are active during encoding, is giving the system a little bit of a boost," Frankland told Sukanya Charuchandra at The Scientist.
“刺激記憶編碼過程中活躍的神經元集合，給系統(tǒng)帶來一點點提升。”Frankland告訴媒體。
"We're providing not only the external cues as the box but also some internal impact as well, which sort of pushes the memory above threshold so then the animals are able to remember it."
“我們不僅提供外部線索作為框架，而且還施加了一些內在影響力，這種方式將記憶推高到閾值以上，以便動物能夠記住它。”
The researchers think that the retrieval of memories is only part of the problem of infant memory loss, and with this incomplete memory recovery, there might also be issues with storage.
研究人員認為，記憶檢索不全只是嬰兒記憶喪失問題的部分答案，并且根據這種不完整的記憶恢復，嬰兒期的記憶存儲也可能存在問題。
But despite this, we don't know if human brains deal with infant memories the same way as they seem to do in mice, so it's best to exercise caution before drawing any major conclusions about our own memory.
但盡管如此，我們還不知道人類大腦的運作機制是否和老鼠相同，所以在得出任何重要結論之前，最好謹慎行事。
Still, the results provide an interesting look into how the brain can store and 'forget' memories from childhood - and it's tantalising to think that our very earliest moments in life might really be locked up in our neurons somewhere.
然而，該實驗至少提供了一個有趣的視角，讓我們了解到大腦是如何存儲和“忘記”童年時代的記憶——并且如果我們生命中最早的人生體驗可能就被鎖在某些失去了檢索目錄的神經元中，有待我們的發(fā)掘，那可真是非常吸引人的想法。
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