Why a ticklish dream could hold the key to psychosis & s

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Why a ticklish dream could hold the key to psychosis & s

Postby emad » Wed Nov 16, 2005 1:10 pm

Why a ticklish dream could hold the key to psychosis and schizophrenia<br><br>In the land of nod we all go a bit psychotic, suggests Dr Raj Persaud<br><br><br><br>Why can't we tickle ourselves? It may seem a trivial question but neuroscientists now believe the answer could provide a clue to the underlying mechanism behind such disorders as schizophrenia. <br><br>This insight follows the recent discovery by Dr Sarah-Jayne Blakemore at University College London that people with schizophrenia are less able to distinguish between self-produced touch and a touch produced by someone else, suggesting they may be more capable of tickling themselves. <br><br>Now, working with a Dr Mark Blagrove of the Department of Psychology, University of Wales, Swansea, and colleagues, she is about to publish a study in the journal Consciousness and Cognition that also shows that you can tickle yourself under some circumstances; basically when you have just been aroused from dreaming sleep.<br><br>The experiment involved waking people up and tickling them. With the help of brainwave-detecting apparatus, some were woken up just after dreaming and others when they weren't dreaming.<br><br>The latest theory why, as the neuroscientists put it, "self-produced tactile stimulation" feels much less tickly than when someone else is doing it is that the brain possesses a mechanism to blot out self produced stimulation to focus on more meaningful sensations generated by events outside the body: it is more important to detect when something landing on your arm than when you move your arm and it brushes against something else. <br><br>Part of this mechanism appears to be the brain making predictions about what should happen next, based on its knowledge that it controls the movement that causes the stimulation.<br><br>While we are dreaming this mechanism is temporarily suspended, as if our minds appear convinced the dream represents external reality. So the monster chasing us in our nightmare appears real no matter how bizarre, contradictory or unrealistic the dream might be.<br><br>In psychosis and schizophrenia it might be that the characteristic symptoms of hallucinations and "passivity experiences" - where sufferers believe their body is being controlled by an outside agency - are explained if once again the mechanism is suspended, as with our everyday dreams.<br><br>As a result, stimuli conjured up by the brain fool the mind into thinking they come from the outside world. A person with schizophrenia fails to appreciate that his inner voice is his own. The utterances are perceived as alien to his mind, and he hears voices. And this is also why sufferers can more successfully tickle themselves.<br><br>It could also be that because this mechanism is turned off during dreaming we do not predict the consequences of our actions during our dreams, there is little sense of anticipation of the future and all experiences seem immediate. In short, this new research suggests that we all go a bit psychotic - and ticklish - every night.<br><br>• Dr Raj Persaud is director of the public engagement unit at the Institute of Psychiatry, King's College London<br> <!--EZCODE AUTOLINK START--><a href="http://www.telegraph.co.uk/connected/main.jhtml?xml=/connected/2005/11/15/ecfraj15.xml&sSheet=/connected/2005/11/15/ixconn.html">www.telegraph.co.uk/conne...xconn.html</a><!--EZCODE AUTOLINK END--> <p></p><i></i>
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