美国英语听力80篇3 Lesson56
Child's Brain
Last month, scientists announced that they recorded the first detailed maps
of the development of a child's brain between the ages of three and fifteen.
Scientists at the University of California at Los Angeles School of Medicine led the group of scientists.
The study appeared in the magazine "Nature".
The researchers say their study provides new information
about what areas of the brain are used in learning at different ages.
The scientists at the University of California invented a process
that let them map brain growth in greater detail than ever before.
They used a machine called an M-R-I to take a picture of the brain of each child in the study.
Using a computer the scientists identified millions of areas of each brain.
They took more pictures of each child's brain during the fouryear study.
Then they mapped the changes in position as the brain developed.
The scientists mainly observed growth in the area of complex nerve tissue called the corpus callosom,
This area sends information between the two halves of the brain.
They say they found that a child's brain experiences two main periods of growth.
The first takes place between the ages of three and six.
The greatest growth appears in an area of the corpus callosom in the front of the brain.
This area is involved in learning new skills,planning and organizing new actions and working on an activity.
The second period of brain growth takes place in the middle and back areas of the corpus callosom from age six to twelve.
The most growth was in the areas of a child's brain involved in language skills and understanding relations in space.
The scientists say it is during these quick growth periods that the brain is best able to learn.
Scientists say the brain overproduces some cells when it grows.
The new cells organize into networks based on the connections that are used in mental or physical activity.
Cells and pathways used often form strong permanent connections.
Those used least die out as the brain returns to its normal size.
Scientists have known that such periods of growth and shrinkage happen before birth and in very early childhood.
And, they knew that the brain network connections continued to change until about the age of five.
But this study and two similar studies released late last year are the first to suggest the process continue to adulthood.
The scientists say their study may explain why the ability to learn new languages generally decreases after the age of twelve.
