美国国家公共电台 NPR Scientists Find A Brain Circuit That Could Explain Seasonal Depression

 

NOEL KING, HOST:

Today is the winter solstice. It's the shortest day of the year, and this is also a time of year when a lot of people feel down or depressed¹. Now scientists think they have new information on why short days lead to such dark moods. NPR's Jon Hamilton has the story.

JON HAMILTON, BYLINE²: About 1 in 5 adults gets the winter blues³ or a more serious problem called seasonal⁴ affective disorder⁵. But scientists haven't been sure whether a lack of daylight is really to blame. Samer Hattar is a researcher at the National Institute of Mental Health.

SAMER HATTAR: People have always wondered if even the effect of light and depression are true.

HAMILTON: Skeptics wanted to know how could light coming in through the eyes mess with brain circuits involved in mood. Hattar says there hasn't been a good answer until now.

HATTAR: It's completely novel. It's completely new, and people have completely missed it.

HAMILTON: The answer involves research that began in the early 2000s when Hattar was at Johns Hopkins University. Back then, most scientists thought that when light struck the retina, only two kinds of cells responded - rods and cones⁶. But Hattar's team was pretty sure there were other light-sensitive cells.

HATTAR: People used to laugh at us if we'd say there are other photoreceptors distinct from rods and cones in the retina.

HAMILTON: The skeptics stopped laughing when the team discovered a third kind of photoreceptor. These cells responded to light, but they didn't seem to help us see. Their most obvious function was keeping the brain's internal clock in sync with changes in daylight. And Hattar says many scientists assumed that this function also explained seasonal depression.

HATTAR: People thought that the only reason you get mood problems is because your clock is misaligned.

HAMILTON: Hattar was pretty sure there was a better reason. And after years of searching, he found one. In September, Hattar's team published a study of mice suggesting a direct pathway between the third kind of photoreceptor and brain areas that affect mood. When the cells were present, artificially shortened days caused a mouse version of depression. On the other hand...

JEROME SANES: If you remove those cells with genetic⁷ tools, the depression-like symptoms go away.

HAMILTON: That's Jerome Sanes, a researcher at Brown University. Sanes wasn't involved in Hattar's study, but he was so intrigued⁸ by the result that he decided⁹ to look for a similar brain circuit in people.

SANES: We studied young adults. We put them into an MRI machine and measured functional¹⁰ MRI signals.

HAMILTON: All while the participants were exposed to different levels of light. This allowed the team to identify brain areas receiving signals from the retina's special photoreceptors. Sanes says two of these areas were way up in the front of the brain.

SANES: It's interesting because these areas seem to be the areas that have been shown in many studies to be involved in depression and other affective disorders¹¹.

HAMILTON: Sanes' team presented their research at the Society for Neuroscience meeting in November. And Samer Hattar says the finding appears to be the last piece in a complex puzzle.

HATTAR: Now you have a circuit - that you know your eye is influencing your brain to affect mood.

HAMILTON: If so, it would explain how shorter days make people sad. Now Hattar says he has a new question. Why would evolution produce a brain that works this way?

HATTAR: You will understand why you would need light to see. But why do you need light to make you happy? We're not plants. Why do we need light to make us happy, and why do we need high-intensity light to make us happy?

HAMILTON: Hattar has no idea, but he hopes to find out. Jon Hamilton, NPR News.

1 depressed   

adj.沮丧的，抑郁的，不景气的，萧条的

参考例句：

• When he was depressed,he felt utterly divorced from reality.他心情沮丧时就感到完全脱离了现实。
• His mother was depressed by the sad news.这个坏消息使他的母亲意志消沉。

2 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

3 blues   

n.抑郁，沮丧；布鲁斯音乐

参考例句：

• She was in the back of a smoky bar singing the blues.她在烟雾弥漫的酒吧深处唱着布鲁斯歌曲。
• He was in the blues on account of his failure in business.他因事业失败而意志消沉。

4 seasonal   

adj.季节的，季节性的

参考例句：

• The town relies on the seasonal tourist industry for jobs.这个城镇依靠季节性旅游业提供就业机会。
• The hors d'oeuvre is seasonal vegetables.餐前小吃是应时蔬菜。

5 disorder   

n.紊乱，混乱；骚动，骚乱；疾病，失调

参考例句：

• When returning back,he discovered the room to be in disorder.回家后，他发现屋子里乱七八糟。
• It contained a vast number of letters in great disorder.里面七零八落地装着许多信件。

6 cones   

n.（人眼）圆锥细胞；圆锥体( cone的名词复数 )；球果；圆锥形东西；（盛冰淇淋的）锥形蛋卷筒

参考例句：

• In the pines squirrels commonly chew off and drop entire cones. 松树上的松鼠通常咬掉和弄落整个球果。 来自辞典例句
• Many children would rather eat ice cream from cones than from dishes. 许多小孩喜欢吃蛋卷冰淇淋胜过盘装冰淇淋。 来自辞典例句

7 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

8 intrigued   

adj.好奇的，被迷住了的v.搞阴谋诡计(intrigue的过去式)；激起…的兴趣或好奇心；“intrigue”的过去式和过去分词

参考例句：

• You've really intrigued me—tell me more! 你说的真有意思—再给我讲一些吧！
• He was intrigued by her story. 他被她的故事迷住了。

9 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。

10 functional   

adj.为实用而设计的，具备功能的，起作用的

参考例句：

• The telephone was out of order,but is functional now.电话刚才坏了，但现在可以用了。
• The furniture is not fancy,just functional.这些家具不是摆着好看的，只是为了实用。

11 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》