医学时文阅读：silent minds

Medical Dispatch

silent Minds

What scanning techniques are revealing about vegetative patients.

by Jerome Groopman October 15, 2007

Brain scans showed one patient was able to imagine playing tennis.

Keywords Vegetative Patients; Comas; Owen, Adrian; Neurology, Neurologists; Brain Scans; Consciousness; Addenbrooke’s Hospital (University of Cambridge)


Ten years ago, Adrian Owen, a young British neuroscientist, was working at a brain-imaging center at Addenbrooke’s Hospital, at the University of Cambridge. He had recently returned from the Montreal Neurological Institute, where he used advanced scanning technology to map areas of the brain, including those involved in recognizing human faces, and he was eager to continue his research. The imaging center was next to the hospital’s neurological intensive-care unit, and Owen heard about a patient there named Kate Bainbridge, a twenty-six-year-old schoolteacher who had become comatose after a flulike illness, and was eventually diagnosed as being in what neurologists call a vegetative state. Owen decided to scan Bainbridge’s brain. “We were looking for interesting patients to study,” he told me. “She was the first vegetative patient I came across.”
For four months, Bainbridge had not spoken or responded to her family or her doctors, although her eyes were often open and roving. (A person in a coma appears to be asleep and is unaware of even painful stimulation; a person in a vegetative state has periods of wakefulness but shows no awareness of her environment and does not make purposeful movements.) Owen placed Bainbridge in a PET scanner, a machine that records changes in metabolism and blood flow in the brain, and, on a screen in front of her, projected photographs of faces belonging to members of her family, as well as digitally distorted images, in which the faces were unrecognizable. Whenever pictures of Bainbridge’s family flashed on the screen, an area of her brain called the fusiform gyrus, which neuroscientists had identified as playing a central role in face recognition, lit up on the scan. “We were stunned,” Owen told me. “The fusiform-gyrus activation in her brain was not simply similar to normal; it was exactly the same as normal volunteers’.”
Excited by this result, Owen resolved to try to conduct brain scans of other vegetative patients in the Cambridge area. Since 1997, he has studied several dozen people, though he decided to use speech sounds rather than photographs to stimulate their brains. (Owen was concerned that showing images of faces might not be a reliable way to test recognition, since the eyes of vegetative patients often wander. “We shifted to auditory responses because you can always put a pair of headphones on the person and know that you are transmitting sound,” he said.) Three years ago, he began using a functional MRI (fMRI) scanner, which is faster than a PET scanner, capturing changes in blood flow in the brain almost as they occur. The patients’ brains were scanned while they listened to a recording of simple sentences interspersed with meaningless “noise sounds.” The scans of some of the patients showed the same response to the sentences as scans of healthy volunteers, but Owen wasn’t sure that the patients had understood the words. “So we went the next step up the cognitive ladder, to look at comprehension,” he said.
Psycholinguists have shown that when we hear a noun at the beginning of a sentence we tend to associate the word with its most common meaning. For example, Owen said, most people hearing a sentence that begins, “The shell was . . .” think of an object typically found at the beach. But if the sentence is completed by the phrase “fired at the tank,” the listener quickly corrects himself, a process that is evident on a brain scan. “You can actually see it happening and image it on the scanner,” Owen said. “The beautiful thing about the psychological task is that we just do it automatically. When you play ambiguous sentences, areas in the inferior frontal lobe and in the posterior temporal lobe become activated, and these areas are very important for speech comprehension. They show that you understand the meaning of the word: it’s not just about perceiving speech; it’s about decoding. Your brain somehow appreciates that there are two meanings to a word like ‘shell.’ ”
Owen eventually identified two vegetative patients whose brains showed the same activity in response to ambiguous sentences as the brains of healthy volunteers. He also took brain scans of healthy physicians, who were presented with the ambiguous sentences while under general anesthesia. Owen found that, as the effects of the anesthesia increased, the physicians showed less activity in the brain regions associated with comprehension. “That, of course, is in keeping with our personal experience of consciousness, which is that as you sort of drift into sleep you understand less and less of what is around you,” he said. (An article about this experiment appears this week in PNAS, the journal of the National Academy of Sciences.)
Owen’s final experiment was the most ambitious: a test to determine whether vegetative patients who seemed able to comprehend speech could also perform a complex mental task on command. He decided to ask them to imagine playing tennis. (“We chose sports, and tried to find one that involved a lot of upper-body movements and not too much running around,” he said.) First, he took brain scans of thirty-four healthy volunteers who were instructed to picture themselves playing the game for at least thirty seconds. Their brains showed activity in a region of the cerebrum that would be stimulated in an actual match. “This was an extremely robust activation, and it wasn’t difficult to tell whether somebody was imagining tennis or not,” Owen said. He then repeated the experiment using one of the vegetative patients, a woman who had been severely injured in a car accident. The woman had to be able to hear and understand Owen’s instructions, retrieve a memory of tennis—including a conception of forehand and backhand and how the ball and the racquet meet—and focus her attention for at least thirty seconds. To Owen’s astonishment, she passed the test. “Lo and behold, she produced a beautiful activation, indistinguishable from those of the group of normal volunteers,” he said. (Another vegetative patient, a man in his twenties, also passed the test, though Owen, having learned that the man was a soccer fan, asked him to imagine playing that sport instead of tennis.)


PHOTOGRAPH: BILL ARMSTRONG, “APPARITION #906” (2005)/CLAMP ART

转自http://www.newyorker.com/reporti ... 015fa_fact_groopman

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冬季，气候寒冷，阴盛阳衰。人体受寒冷气温的影响，机体的生理功能和食欲等均会发生变化。因此，合理地调整饮食，保证人体必需营养素的充足，对提高老人的耐寒能力和免疫功能，使之安全、顺利地越冬，是十分必要的。

　　首先应保证热能的供给。冬天的寒冷气候影响人体的内分泌系统，使人体的甲状腺素、肾上腺素等分泌增加，从而促进和加速蛋白质、脂肪、碳水化合物三大类热源营养素的分解，以增加机体的御寒能力，这样就造成人体热量散失过多。因此，冬天营养应以增加热能为主，可适当多摄入富含碳水化合物和脂肪的食物。对于老年人来说，脂肪摄入量不能过多，以免诱发老年人的其它疾病，但应摄入充足的蛋白质，因为蛋白质的分解代高谢增强，人体易出现负氮平衡。蛋白质的供给量以占总热量的15～17%为好，所供给的蛋白质应以优质蛋白质为主，如瘦肉、鸡蛋、鱼类、乳类、豆类及其制品等，这些食物所含的蛋白质，不仅便于人体消化吸收，而且富含必需氨基酸，营养价值较高，可增加人体的耐寒和抗病能力。

　　冬天，又是蔬菜的淡季，蔬菜的数量既少，品种也较单调，尤其是在我国北方，这一现象更为突出。因此，往往一个冬季过后，人体出现维生素不足，如缺乏维生素C、并因此导致不少老人发生口腔渍疡、牙根肿痛、出血、大便秘结等症状。其防治方法首先应扩大食物来源，冬天绿叶菜相对减少，可适当吃些薯类，如甘薯、马铃薯等。它们均富含维生素C，维生素B，特别是缺乏维生素A，红心甘薯还含较多的胡萝卜素。多吃薯类，不仅可补充维生素，还有清内热、去瘟毒作用。此外，在冬季上市的大路菜中，除大白菜外，还应选择圆白菜、心里美萝卜、白萝卜、胡萝卜、黄豆芽、绿豆芽、油菜等。这些蔬菜中维生素含量均较丰富。只要经常调换品种，合理搭配，还是可以补充人体维生素需要的。冬季的寒冷，还可影响人体的营养代谢，使各种营养素的消耗量均有不同程度的增加。老年人由于消化吸收和体内代谢因素的影响，往往缺乏钾、钙、钠、铁等元素，再加上冬季人体尿量增多，使上述无机盐随尿液排出的量也增多，因此，应及时予以补充。可多吃些含钙、铁、钠、钾等丰富的食物，如虾米、虾皮、芝麻酱、猪肝、香蕉等。如有钠低者，做菜时，口味稍偏咸，即可补充。

怎么没有翻译呀

医学英语很有用啊