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4 How many states of consciousness are there?
HOW MANY STATES OF CONSCIOUSNESS ARE THERE?
4
YOU might think consciousness is like a light switch, either on or off. But the true picture now seems rather murkier, challenging our notions of awareness and free will, as well as raising issues of consent in coma patients. People used to think just three states of consciousness existed, says Adam Zeman of the Peninsular Medical School in Exeter, UK. “You’re either awake or asleep – and if you’re asleep you’re either in dream or nondream sleep.” But brain imaging suggests there are more. Take sleepwalking, which affects as many as 1 in 20 adults. “The sleepwalking brain is literally in a half-awake, halfasleep state,” says Zeman. Researchers once manoeuvred a sleepwalker into a brain scanner, and while they saw that much of
the cortex – involved in awareness and consciousness – was offline, other brain areas were active, including those linked with emotion. Similar overlaps might explain other weird states of consciousness. In dreaming sleep – also known as REM sleep – we lie still because an area of the brainstem called the pons blocks signals to the muscles. People with REM behaviour disorder lose this inhibition and physically act out their dreams. The opposite condition, known as sleep paralysis, occurs if people wake up while still unable to move. There may also be some hitherto unnoticed stopping-off points in the twilight between consciousness and coma. In February, a team led by Adrian Owen at the University of
CHRIS STOWERS/PANOS
Yoga may boost physical health via the immune system
HOW POWERFUL IS THE MIND-BODY CONNECTION?
30 | NewScientist | 3 April 2010
5
Cambridge discovered that it was possible to communicate with a man in a vegetative state – in which someone has intact reflexes and can breathe unaided, but seems completely unaware of their surroundings. By asking him to visualise playing tennis or moving around his house as he lay in a brain scanner, they were able to elicit yes or no answers from him. Such patients are currently treated as unconscious, but if they can understand questions and communicate, they might be able to express opinions about their treatment – and whether or not it should be withdrawn. We may not yet know how many states of consciousness there are, but the nature of consciousness is looking increasingly like a ladder rather than a light switch. Linda Geddes
IF YOU’RE unlucky enough to be staying in hospital, try to get a room with a view. You may recover quicker if you overlook a grove of trees rather than a brick wall. The study of the links between mind and body is as old as the practice of medicine. Wise doctors know, for example, to probe the mental state of a patient whose symptoms are hard to explain physically. And we have all heard of cases where a bereavement or divorce seems to have triggered the onset of illness. Yet considering how much we take such links for granted, their mechanisms remain mysterious. Why are some diseases more influenced by mental state than others? What’s behind the mind-boggling placebo effect? Could we ever learn to think ourselves well? Many of these effects seem to be mediated by the immune system. Severe stress has been shown to reduce immune cell activity, both in the test tube and in people. There seem to be several ways in which the brain influences the immune system, from chemical mediators to direct neural control. One branch of the vagus nerve connects the brain to a key regulator of immune functioning, says Kevin Tracey of the Feinstein Institute for Medical Research in Manhasset, New York. “Signals that originate in the brain travel down the vagus nerve where they change the behaviour of immune cells in the spleen,” he says (Nature, vol 420, p 853). Tracey’s team has since found that electrically stimulating the vagus nerve decreases inflammation, a state of immune system high-alert implicated in a large number of diseases, including cancer. They suspect there may be other nerve-immune links that have the effect of “turning up” inflammation. If we can’t consciously control the immune system, we might at least be able to manipulate it with drugs or perhaps via the vagus nerve. Linda Geddes
4
YOU might think consciousness is like a light switch, either on or off. But the true picture now seems rather murkier, challenging our notions of awareness and free will, as well as raising issues of consent in coma patients. People used to think just three states of consciousness existed, says Adam Zeman of the Peninsular Medical School in Exeter, UK. “You’re either awake or asleep – and if you’re asleep you’re either in dream or nondream sleep.” But brain imaging suggests there are more. Take sleepwalking, which affects as many as 1 in 20 adults. “The sleepwalking brain is literally in a half-awake, halfasleep state,” says Zeman. Researchers once manoeuvred a sleepwalker into a brain scanner, and while they saw that much of
the cortex – involved in awareness and consciousness – was offline, other brain areas were active, including those linked with emotion. Similar overlaps might explain other weird states of consciousness. In dreaming sleep – also known as REM sleep – we lie still because an area of the brainstem called the pons blocks signals to the muscles. People with REM behaviour disorder lose this inhibition and physically act out their dreams. The opposite condition, known as sleep paralysis, occurs if people wake up while still unable to move. There may also be some hitherto unnoticed stopping-off points in the twilight between consciousness and coma. In February, a team led by Adrian Owen at the University of
CHRIS STOWERS/PANOS
Yoga may boost physical health via the immune system
HOW POWERFUL IS THE MIND-BODY CONNECTION?
30 | NewScientist | 3 April 2010
5
Cambridge discovered that it was possible to communicate with a man in a vegetative state – in which someone has intact reflexes and can breathe unaided, but seems completely unaware of their surroundings. By asking him to visualise playing tennis or moving around his house as he lay in a brain scanner, they were able to elicit yes or no answers from him. Such patients are currently treated as unconscious, but if they can understand questions and communicate, they might be able to express opinions about their treatment – and whether or not it should be withdrawn. We may not yet know how many states of consciousness there are, but the nature of consciousness is looking increasingly like a ladder rather than a light switch. Linda Geddes
IF YOU’RE unlucky enough to be staying in hospital, try to get a room with a view. You may recover quicker if you overlook a grove of trees rather than a brick wall. The study of the links between mind and body is as old as the practice of medicine. Wise doctors know, for example, to probe the mental state of a patient whose symptoms are hard to explain physically. And we have all heard of cases where a bereavement or divorce seems to have triggered the onset of illness. Yet considering how much we take such links for granted, their mechanisms remain mysterious. Why are some diseases more influenced by mental state than others? What’s behind the mind-boggling placebo effect? Could we ever learn to think ourselves well? Many of these effects seem to be mediated by the immune system. Severe stress has been shown to reduce immune cell activity, both in the test tube and in people. There seem to be several ways in which the brain influences the immune system, from chemical mediators to direct neural control. One branch of the vagus nerve connects the brain to a key regulator of immune functioning, says Kevin Tracey of the Feinstein Institute for Medical Research in Manhasset, New York. “Signals that originate in the brain travel down the vagus nerve where they change the behaviour of immune cells in the spleen,” he says (Nature, vol 420, p 853). Tracey’s team has since found that electrically stimulating the vagus nerve decreases inflammation, a state of immune system high-alert implicated in a large number of diseases, including cancer. They suspect there may be other nerve-immune links that have the effect of “turning up” inflammation. If we can’t consciously control the immune system, we might at least be able to manipulate it with drugs or perhaps via the vagus nerve. Linda Geddes