美国英语听力80篇3 Lesson56

（单词翻译）

[00:05.75]Last month, scientists announced that they recorded the first detailed¹ maps
[00:13.06]of the development of a child's brain between the ages of three and fifteen.
[00:19.98]Scientists at the University of California at Los Angeles School of Medicine led the group of scientists.
[00:29.68]The study appeared in the magazine "Nature".
[00:34.01]The researchers say their study provides new information
[00:39.42]about what areas of the brain are used in learning² at different ages.
[00:45.22]The scientists at the University of California invented a process
[00:52.17]that let them map brain growth in greater detail than ever before.
[00:57.31]They used a machine called an M-R-I to take a picture of the brain of each child in the study.
[01:06.14]Using a computer the scientists identified millions of areas of each brain.
[01:13.64]They took more pictures of each child's brain during the fouryear study.
[01:20.61]Then they mapped the changes in position as the brain developed.
[01:25.03]The scientists mainly observed growth in the area of complex nerve³ tissue⁴ called the corpus callosom,
[01:34.75]This area sends information between the two halves of the brain.
[01:40.28]They say they found that a child's brain experiences two main periods of growth.
[01:48.09]The first takes place between the ages of three and six.
[01:53.53]The greatest growth appears in an area of the corpus callosom in the front of the brain.
[02:00.76]This area is involved in learning new skills,planning and organizing new actions and working on an activity.
[02:09.78]The second period of brain growth takes place in the middle and back areas of the corpus callosom from age six to twelve.
[02:20.77]The most growth was in the areas of a child's brain involved in language skills and understanding relations in space.
[02:30.54]The scientists say it is during these quick growth periods that the brain is best able to learn.
[02:39.11]Scientists say the brain overproduces some cells when it grows.
[02:45.38]The new cells organize into networks based on the connections that are used in mental or physical activity.
[02:55.96]Cells and pathways used often form strong permanent connections.
[03:02.67]Those used least die out as the brain returns to its normal size.
[03:09.86]Scientists have known that such periods of growth and shrinkage happen before birth and in very early childhood.
[03:20.91]And, they knew that the brain network connections continued to change until about the age of five.
[03:29.97]But this study and two similar studies released⁵ late last year are the first to suggest the process continue to adulthood⁶.
[03:40.71]The scientists say their study may explain why the ability to learn new languages generally decreases after the age of twelve