Thought research stirs up ethical debate
In an experiment with profound medical and ethical implications, neuroscientists have for the first time enabled an apparently unconscious patient in a persistent vegetative state to communicate through her thoughts.
A woman who suffered severe head injury in a road accident last year - and seemed unable to communicate or respond to any stimulus - played tennis in her head and made a mental tour of her home, when requested to do so by the research team in Cambridge.
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"These are startling results," said Adrian Owen of the Medical Research Council's brain sciences unit, who led the project. The 23-year-old patient's mental activity was mapped through functional magnetic resonance imaging.
"Despite the diagnosis of vegetative state, this patient retained the ability to understand spoken commands and to respond to them through her brain activity, rather than through speech or movement," said Dr Owen. "Her decision to work with us by imagining particular tasks when asked represents a clear act of intent which confirmed beyond any doubt that she was consciously aware of herself and hersurroundings."
The results will stir up the ethical debate about how to treat patients who have been in a vegetative state for a long time and in what circumstances to turn off their life support.
Narender Ramnani, reader in cognitive neuroscience at Royal Holloway University of London, said: "Given that such patients might be conscious and capable of making their own decisions, is it acceptable for others to terminate their lives without their consent?"
In an unusual editorial, Science, the journal publishing the Cambridge study today, refers to the political storm in the US over last year's death of Terri Schiavo when her feeding tube was removed after 15 years in a vegetative state.
The paper "presents a single case study and therefore should not be used to generalise about all other patients in a vegetative state, particularly since each case may involve a different type of injury," it said.
The Cambridge scientists used a ￡1.2m FMRI machine to map the patient's brain responses to spoken sentences. These showed that she recognised speech at some level but did not prove she was consciously aware.
Then she was asked to imagine in sequence playing tennis and walking round every room in her house. The brain images were identical to those of healthy volunteers thinking about the same two activities and, according to Dr Owen, were unambiguous.
Further development of the technique might allow doctors to identify patients who have some level of awareness, he said, "but we would have to be extremely careful about how we interpreted negative results. Lack of response would not necessarily mean lack of awareness; for example a patient's auditory system might not be working".
英国研究人员：植物人有思维
神经科学家进行了一次在医学和伦理学方面意义深远的试验，并首次让一位明显丧失意识、处于持续植物状态(persistent vegetative state)的病人通过其思维进行了交流。
一位去年在道路交通事故中头部受伤的妇女看似无法进行交流，对任何刺激都没有反应，但她应剑桥大学研究团队的要求，在自己脑海中打了网球并神游了自己的家。
“这些结果令人吃惊，”剑桥医学研究委员会脑科学组(Medical Research Council Brain Sciences Unit)的阿德里安?欧文(Adrian Owen)表示。该科学组领导了这一项目。这位23岁女性病人的大脑活动，已通过功能核磁共振成像(fMRI)技术制图。
“尽管这名病人被诊断为植物状态，但她保留了理解口头指令并通过大脑活动、而非语音或动作做出反应的能力，”欧文表示。“她决定与我们合作，根据我们的指令想象特定的任务，这是一个清楚的意向行为，确凿无疑地证明，她有意识地认知自己和周围环境。”
他表示，如果该技术得到进一步发展，医生也许就能找出有一定认知能力的病人，“但在解释负面结果时，我们须极其小心。没有反应并不一定意味着没有认知能力，例如，病人的听觉系统可能有问题。”
这些结果将引起关于两个问题的伦理辩论，即如何对待处于植物状态已有一段时间的病人，以及在何种情况下可以切断他们的生命支持系统。
“鉴于这些病人可能有意识，并能够自己做决定，他人未经他们同意，就结束他们的生命，这样做能让人接受吗？”伦敦大学皇家霍洛威学院(Royal Holloway University of London)认知神经科学专业高级讲师纳伦德?拉姆纳尼(Narender Ramnani)问道。
