新记忆究竟如何形成?

记忆究竟如何形成?过程乱了套会怎样?如今,神经科学家对此有了突破性的洞见。研究人员对意识清醒的老鼠进行实验,研究其新生大脑细胞。该过程被称为“成体神经发生”,即产生新的神经元,并整合进当前的回路中。
神经科学副教授、论文的高级作者Attila Losonczy解释道:
通过此方法,我们得以对活动物大脑的新生细胞和成熟细胞的活动进行比较。研究结果有助于科学家破解“成体神经发生”在健康和疾病中所起的作用。
这回,研究人员所关注的大脑区域为“齿状回”,这是大脑深处的一个小结构——由于埋藏得很深,因此研究起来十分困难。同时,它是少数几个在出生之后仍能继续长出新细胞的区域之一(绝大部分大脑细胞在出生前就已形成)。
不过,我们并不太理解此处为何会长出新细胞。这是神经科学中的一个未解大谜团:为何大自然决定要在“齿状回”中补充新细胞,而非其它大脑部位?
之前的研究表明,大脑之所以能够区分出熟悉的新环境(该过程被称为“模组分离”),齿状回及其细胞可能是其中的原因。“模组分离”是大脑内部GPS的不可或缺的一部分,它使我们能够记住相似但不同的新地点。
Mazen Kheirbek表示,以往的研究无法如此详细地描绘出齿状回的图像,更不必说其中的单个细胞了。如今,其团队表明,这些成体新生颗粒细胞和周围成熟细胞的活动模式不同。具体而言,这些细胞的独特活动模式的差异在于:出生过后不久,它们便比成熟细胞表现出更高的兴奋性。六周过后,这一现象逐渐减少。不过,其最初的亢奋为科学家进一步理解记忆和模组分离提供了线索。
研究显示,这些成体新生颗粒细胞不仅可以编码新经验的记忆,还能判断两次经验是否不同。理解成体新生颗粒细胞对活大脑的行为影响非常重要,它有助于我们将来利用此过程进行治疗。

http://www.sciencealert.com/scientists-get-their-first-glimpse-at-how-new-memories-are-born

Scientists get their first glimpse at how new memories are born

Our brains are incredible.

Neuroscientists have gained unprecedented insight into how memories are formed - and what happens when that process goes haywire.

Led by a team from Colombia’s Mortimer B. Zuckerman Mind Brain Behaviour Institute and the Columbia University Medical Centre (CUMC), the study was conducted on newly generated brain cells in conscious mice. This process (of generating new neurons that integrate into existing circuits) is known as 'adult neurogenesis'.

Attila Losonczy, senior author on the paper and assistant professor of neuroscience, explained the significance. He asserts: "Our approach allows us to compare the activity of newborn and mature cells in the brains of behaving animals. These findings could help scientists decipher the role that adult neurogenesis plays in both health and disease."

The region of the brain that these researchers are focused on is known as the dentate gyrus, a small structure buried deep within the brain, making it difficult to study. This region is also one of the very few areas that is able to continue to grow new cells after birth (most brain cells are made before one is born).

However, we don’t really understand why new cells are produced here. "One of the great unanswered questions in neuroscience is, why did nature decide to replenish cells in this region of the brain, but not others?" says Losonczy.

This research may help us answer this question.

Previous studies on the dentate gyrus and its cells suggested that they could be responsible for how the brain is able to differentiate between familiar yet new environments, which is a process known as pattern separation. This process is integral to your brain’s internal GPS and allows you to remember locations that look alike but are otherwise new ground.

Mazen Kheirbek explains that previous research has failed to image the dentate gyrus at this level of detail, to say nothing of imaging the individual cells that reside within it. Now, their team was able to show that adult-born granule cells act differently than their mature neighbours, and they determined why that difference is so critical.

Specifically, the difference is in the unique activity pattern of adult-born granule cells that, shortly after they are born, exhibit a heightened excitability compared to more mature cells. This activity tapers off after six weeks, but that initial burst offers clues to understanding memories and pattern separation.

"These findings reveal that adult-born granule cells are required not only to encode the memory of a new experience, but also to determine whether one experience is different from the next," said Kheirbek.

René Hen, professor of neuroscience and pharmacology (in psychiatry) at CUMCsaid that "understanding how adult-born granule cells impact behaviour in the living brain is an important step toward one day harnessing this process for therapeutic purposes".

Their findings are published in the journal Neuron.


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