幼儿记忆或被唤醒
你最初的记忆是在什么时候?你永远不会拥有婴儿时期的记忆——大多数人最早的记忆都是在三四岁开始。
But why can we not remember our infant memories? And are they really lost, or just forgotten?
但为什么我们记不起自己的婴儿时期了呢?它们真的丢失了，还是只是被遗忘在某处角落里?
A team of neuroscientists from the University of Toronto set out to investigate, using mice to identify when and how brains forget these memories.
来自多伦多大学的神经科学家团队就此展开了调查。他们用老鼠来设计实验，希望追踪到早期记忆的遗忘过程。
"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.
他们在研究中写道，“人们猜测，早期记忆被快速遗忘的原因是，儿童缺乏巩固和组织自我记忆的认知工具。”
"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，在包括小鼠在内的非人类物种中也观察到类似的婴儿期遗忘现象，这就表明现象背后存在着完整的神经生物学机理。”
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.
研究人员训练新生小鼠将一个特定的盒子与对其足部的击打联系起来。老鼠在15天内就失去了对击打的记忆，这几乎相当于于人类在7岁左右忘记了婴儿期的记忆。
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.
研究人员随后换了一组新的幼鼠，并在训练中，找到它们海马体内活动的神经元并标记出来。
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.
几周之后，当记忆被遗忘时，研究人员使用光遗传学技术精确地刺激标记处的神经元，他们发现老鼠的表现行为就好像他们再次识别了这个盒子一样。
"The memory recall was remarkable," says senior author Paul Frankland, a neurobiologist from the SickKids Research Institute, and the University of Toronto.
“可被召回的记忆非常引人注目。”资深作者Paul Frankland说，他是儿童病理医学研究所和多伦多大学的神经生物学家。
"These results suggest our earliest experiences are not completely forgotten or erased from the brain. Instead, we can bring them back through direct stimulation."
“这些结果表明，我们最早的人生经历并没有完全被大脑遗忘或清除。相反，我们可以通过直接的刺激将它们带回来。”
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。在接下来的15-90天内，只有约70%的小鼠能够再次识别出这个盒子，研究人员认为这与记忆恢复不完全有关。
"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.
“刺激记忆编码过程中活跃的神经元集合，给系统带来一点点提升。”Frankland告诉媒体。
"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."
“我们不仅提供外部线索作为框架，而且还施加了一些内在影响力，这种方式将记忆推高到阈值以上，以便动物能够记住它。”
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.
研究人员认为，记忆检索不全只是婴儿记忆丧失问题的部分答案，并且根据这种不完整的记忆恢复，婴儿期的记忆存储也可能存在问题。
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.
但尽管如此，我们还不知道人类大脑的运作机制是否和老鼠相同，所以在得出任何重要结论之前，最好谨慎行事。
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，该实验至少提供了一个有趣的视角，让我们了解到大脑是如何存储和“忘记”童年时代的记忆——并且如果我们生命中最早的人生体验可能就被锁在某些失去了检索目录的神经元中，有待我们的发掘，那可真是非常吸引人的想法。
