Scans reveal the brain's early growth, late decline and surprising variability

Scans reveal the brain's early growth, late decline and surprising variability

Transcript¹

The human brain starts with a bang and ends with a whimper.

That's the conclusion of a project that used more than 120,000 brain scans to chart the organ's changes throughout the lifespan. The results appear in the April 6 issue of the journal Nature.

Among the key findings:

The brain reaches 80% of its maximum size by age 3.

The volume of gray matter, which represents brain cells, peaks before age 6.

The volume of white matter — a way of measuring the connections between brain cells — peaks before age 29.

The loss of white matter accelerates after age 50.

The ongoing² study could eventually lead to brain growth charts that would allow doctors to look for signs of atypical development in young patients. But for now, the results are meant for scientists who study typical brain growth or brain disorders³ like schizophrenia and Alzheimer's disease.

One goal is to "use this huge amount of existing data to help understand and treat psychiatric diseases," says one of the study's authors Dr. Aaron Alexander-Bloch, a psychiatrist⁴ at the University of Pennsylvania and Children's Hospital of Philadelphia.

The project began more than six years ago when two young researchers at a scientific conference began talking about a simple question: How does a person's brain change during their lifespan?

They realized there was no good answer because most studies that involved MRI brain scans had been limited to a small number of people at a single point in time. Also, the studies used different designs and kept their data in different forms.

So the researchers had an idea.

Researchers decided⁵ to turn more than 100 small studies into one big one

"We could just stitch together all these other studies and all these common data sets to create some sort of ground truth and a common language," says Richard Bethlehem, a research associate in the psychiatry⁶ department at the University of Cambridge.

Bethlehem and Jakob Seidlitz, a postdoctoral researcher at the University of Pennsylvania and Children's Hospital of Philadelphia, began asking other researchers if they would contribute their study data to the effort.

"And really everyone came back and said, 'This looks great, we should definitely be doing this,'" Seidlitz says.

The pair assembled an international team and began the hard work of turning more than 100 small studies into one big one.

"Richard and I spent months literally⁷ just curating a lot of these data sets," Seidlitz says.

They began to realize how different brains can be

Eventually, they had brain scan data from more than 100,000 individuals, ranging from a fetus⁸ to a centenarian. And when they analyzed⁹ the data, they began to realize how different brains could be.

"One of the fundamental things that we started to see was just the sheer variability of how big the brain gets throughout development," Seidlitz says.

The team also found variation in the growth patterns of several dozen different areas of the brain's outermost¹⁰ layer and in the volume of white matter, gray matter, subcortical gray matter and in the fluid-filled cavities known as ventricles.

Despite its huge size, the study still has gaps, the researchers say, including a lack of racial and ethnic¹¹ diversity. "That's one of the things we've been humbled¹² by," he says.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 ongoing   

adj.进行中的，前进的

参考例句：

• The problem is ongoing.这个问题尚未解决。
• The issues raised in the report relate directly to Age Concern's ongoing work in this area.报告中提出的问题与“关心老人”组织在这方面正在做的工作有直接的关系。

3 disorders   

n.混乱( disorder的名词复数 )；凌乱；骚乱；（身心、机能）失调

参考例句：

• Reports of anorexia and other eating disorders are on the increase. 据报告，厌食症和其他饮食方面的功能紊乱发生率正在不断增长。 来自《简明英汉词典》
• The announcement led to violent civil disorders. 这项宣布引起剧烈的骚乱。 来自《简明英汉词典》

4 psychiatrist   

n.精神病专家；精神病医师

参考例句：

• He went to a psychiatrist about his compulsive gambling.他去看精神科医生治疗不能自拔的赌瘾。
• The psychiatrist corrected him gently.精神病医师彬彬有礼地纠正他。

5 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

6 psychiatry   

n.精神病学，精神病疗法

参考例句：

• The study appeared in the Amercian science Journal of Psychiatry.这个研究发表在美国精神病学的杂志上。
• A physician is someone who specializes in psychiatry.精神病专家是专门从事精神病治疗的人。

7 literally   

adv.照字面意义，逐字地；确实

参考例句：

• He translated the passage literally.他逐字逐句地翻译这段文字。
• Sometimes she would not sit down till she was literally faint.有时候，她不走到真正要昏厥了，决不肯坐下来。

8 fetus   

n.胎，胎儿

参考例句：

• In the fetus,blood cells are formed in different sites at different ages.胎儿的血细胞在不同时期生成在不同的部位。
• No one knows why a fetus is not automatically rejected by the mother's immune system. 没有人知道为什么母亲的免疫系统不会自动排斥胎儿。

9 analyzed   

v.分析( analyze的过去式和过去分词 )；分解；解释；对…进行心理分析

参考例句：

• The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
• The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程，因为对他来说，爱是个不可分析的迷。 来自《简明英汉词典》

10 outermost   

adj.最外面的，远离中心的

参考例句：

• He fired and hit the outermost ring of the target.他开枪射中了靶子的最外一环。
• The outermost electron is shielded from the nucleus.原子核对最外层电子的作用受到屏蔽。

11 ethnic   

adj.人种的，种族的，异教徒的

参考例句：

• This music would sound more ethnic if you played it in steel drums.如果你用钢鼓演奏，这首乐曲将更具民族特色。
• The plan is likely only to aggravate ethnic frictions.这一方案很有可能只会加剧种族冲突。

12 humbled   

adj. 卑下的，谦逊的，粗陋的 vt. 使 ... 卑下，贬低

参考例句：

• The examination results humbled him. 考试成绩挫了他的傲气。
• I am sure millions of viewers were humbled by this story. 我相信数百万观众看了这个故事后都会感到自己的渺小。