This synaptic pruning, as it is called, causes the brain's cortex-the outer layer of gray matter where we do much of our conscious and complicated thinking-to become thinner but more efficient.

我们称之为突触的自我修剪，保持意识清醒和用来复杂思维的大脑皮层，外面的灰质外层变得更薄但更高效。

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The outer layer of the cerebrum is called the cortex (also known as "gray matter").

大脑外层叫做皮质(也称“灰质”)。

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Cerebral cortex: layer of gray matter that constitutes the outer layer of the cerebrum and is responsible for integrating sensory impulses and for higher intellectual functions.

大脑皮质：指大脑外层的灰质层，负责整合感觉冲动和各种高级智力活动。

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