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Brain scans reveal why some people feel your pain
THIS WEEK
No inhibition in feeling others’ pain to help us to understand other people’s actions and emotions. But the activation is not as strong as that caused by real pain because inhibitory mechanisms normally dampen the response.
FOR some people, seeing pain in someone else is more than emotionally distressing: they feel the pain in their own body too. Now some of the pathways involved have been identified. “Synaesthetic pain” occurs mainly in people who have lost a limb. Some amputees are already known to experience phantom limb pain – a feeling of pain in a limb that is no longer there – but synaesthetic pain is different. Rather than occurring spontaneously, it is triggered by observed or imagined pain. “When I hear my husband’s power tools, or see a knife, I often get a sharp pain through my phantom leg,” says Jane Barrett, who has experienced synaesthetic pain since losing her leg in a motorcycle accident. When we observe or imagine pain, it activates areas of the brain involved in the processing of real pain. This is called the mirror neuron system and is thought
Call to delay judgement on cellphone risk A DEFINITIVE assessment of whether cellphones pose a risk of brain cancer to their users should be put on hold, campaigners are claiming. The mainstream view is that there is no evidence for any such risk. But pressure groups want the World Health Organization’s International Agency for Research on Cancer (IARC) to delay a decision on the issue. They say that only half the data from the 13-country Interphone study of brain cancer and cellphone use, 12 | NewScientist | 28 May 2011
Enrico Fianchini/getty
Helen Thomson
collected in 2004, has been published. The IARC is due to decide the issue at a meeting in Lyon, France, which finishes next week. Data issued last year showed no evidence of any major risk of cancer from cellphone use. However, the campaigners say that Interphone data from individual countries and on other types of cancer, such as those of the parotid gland, has not yet been published or taken into account in establishing overall risks. “It’s irresponsible not to publish it all,” says Alasdair Philips of the lobby group Powerwatch UK, who is a co-signatory of a letter organised by the International EMF Alliance in Oslo, Norway, calling for the decision to be
Bernadette Fitzgibbon at Monash University in Melbourne, Australia, and colleagues, think those inhibitory mechanisms are themselves inhibited in pain synaesthetes. They used EEG to record brain activity in eight amputees who experience both phantom and synaesthetic pain, 10 amputees who experience just phantom pain and 10 healthy people with no amputations while they looked
at images of hands or feet in potentially painful and nonpainful situations. When viewing the images, pain synaesthetes exhibited decreased theta and alpha brainwaves compared with the other volunteers. Such a decrease reflects an increase in neural activity, suggesting that their mirror systems are activated more strongly (Social Cognitive and Affective Neuroscience, DOI: 10.1093/scan/nsr016). Fitzgibbon says the traumatic experience associated with losing a limb may heighten the sensitivity of pain synaesthetes to others’ pain. When threatened, our body naturally becomes hypervigilant to pain: our pain threshold lowers, which can make even small triggers painful. Pain synaesthesia may be a symptom of an abnormal, ongoing hypervigilance. Michael Banissy at University College London welcomes the new “building block” in our understanding of the condition. “The suggestion that acquired mirror-pain synaesthesia may be mediated by neural disinhibition is intriguing. It implies that plasticity in neural systems involved in our ability to process observed pain can –Just the thought of it…– trigger actual pain.” n
postponed. “We’re not looking for a mobile phone ban, but we should have much more sensible guidelines on usage,” Philips says. The IARC says that all necessary Interphone brain-cancer data was published. “Interphone was designed as a multi-country study to provide sufficient statistical power, so the single-country analyses requested by the EMF Alliance are not warranted,” IARC spokesman Nicolas Gaudin says. Some animal studies suggest that cellphone radiation can damage cells.
“We’re not looking for a mobile phone ban, but we should have more sensible guidelines on usage”
Nesrin Seyhan at Gazi University in Ankara, Turkey, showed that it could damage DNA in rabbits and their offspring. “We found significantly elevated patterns of damage in exposed compared to non-exposed animals, including DNA modification and other accepted biomarkers of increased risk of cancer,” she says (General Physiology and Biophysics, DOI: 10.4149/gpb_2010_01_59). Lukas Margaritis of the University of Athens, Greece, says cellphone radiation also impairs short-term memory in mice (Pathophysiology, DOI: 10.1016/j. pathophys.2010.11.001). Whether these studies translate to humans has yet to be determined. Andy Coghlan n
No inhibition in feeling others’ pain to help us to understand other people’s actions and emotions. But the activation is not as strong as that caused by real pain because inhibitory mechanisms normally dampen the response.
FOR some people, seeing pain in someone else is more than emotionally distressing: they feel the pain in their own body too. Now some of the pathways involved have been identified. “Synaesthetic pain” occurs mainly in people who have lost a limb. Some amputees are already known to experience phantom limb pain – a feeling of pain in a limb that is no longer there – but synaesthetic pain is different. Rather than occurring spontaneously, it is triggered by observed or imagined pain. “When I hear my husband’s power tools, or see a knife, I often get a sharp pain through my phantom leg,” says Jane Barrett, who has experienced synaesthetic pain since losing her leg in a motorcycle accident. When we observe or imagine pain, it activates areas of the brain involved in the processing of real pain. This is called the mirror neuron system and is thought
Call to delay judgement on cellphone risk A DEFINITIVE assessment of whether cellphones pose a risk of brain cancer to their users should be put on hold, campaigners are claiming. The mainstream view is that there is no evidence for any such risk. But pressure groups want the World Health Organization’s International Agency for Research on Cancer (IARC) to delay a decision on the issue. They say that only half the data from the 13-country Interphone study of brain cancer and cellphone use, 12 | NewScientist | 28 May 2011
Enrico Fianchini/getty
Helen Thomson
collected in 2004, has been published. The IARC is due to decide the issue at a meeting in Lyon, France, which finishes next week. Data issued last year showed no evidence of any major risk of cancer from cellphone use. However, the campaigners say that Interphone data from individual countries and on other types of cancer, such as those of the parotid gland, has not yet been published or taken into account in establishing overall risks. “It’s irresponsible not to publish it all,” says Alasdair Philips of the lobby group Powerwatch UK, who is a co-signatory of a letter organised by the International EMF Alliance in Oslo, Norway, calling for the decision to be
Bernadette Fitzgibbon at Monash University in Melbourne, Australia, and colleagues, think those inhibitory mechanisms are themselves inhibited in pain synaesthetes. They used EEG to record brain activity in eight amputees who experience both phantom and synaesthetic pain, 10 amputees who experience just phantom pain and 10 healthy people with no amputations while they looked
at images of hands or feet in potentially painful and nonpainful situations. When viewing the images, pain synaesthetes exhibited decreased theta and alpha brainwaves compared with the other volunteers. Such a decrease reflects an increase in neural activity, suggesting that their mirror systems are activated more strongly (Social Cognitive and Affective Neuroscience, DOI: 10.1093/scan/nsr016). Fitzgibbon says the traumatic experience associated with losing a limb may heighten the sensitivity of pain synaesthetes to others’ pain. When threatened, our body naturally becomes hypervigilant to pain: our pain threshold lowers, which can make even small triggers painful. Pain synaesthesia may be a symptom of an abnormal, ongoing hypervigilance. Michael Banissy at University College London welcomes the new “building block” in our understanding of the condition. “The suggestion that acquired mirror-pain synaesthesia may be mediated by neural disinhibition is intriguing. It implies that plasticity in neural systems involved in our ability to process observed pain can –Just the thought of it…– trigger actual pain.” n
postponed. “We’re not looking for a mobile phone ban, but we should have much more sensible guidelines on usage,” Philips says. The IARC says that all necessary Interphone brain-cancer data was published. “Interphone was designed as a multi-country study to provide sufficient statistical power, so the single-country analyses requested by the EMF Alliance are not warranted,” IARC spokesman Nicolas Gaudin says. Some animal studies suggest that cellphone radiation can damage cells.
“We’re not looking for a mobile phone ban, but we should have more sensible guidelines on usage”
Nesrin Seyhan at Gazi University in Ankara, Turkey, showed that it could damage DNA in rabbits and their offspring. “We found significantly elevated patterns of damage in exposed compared to non-exposed animals, including DNA modification and other accepted biomarkers of increased risk of cancer,” she says (General Physiology and Biophysics, DOI: 10.4149/gpb_2010_01_59). Lukas Margaritis of the University of Athens, Greece, says cellphone radiation also impairs short-term memory in mice (Pathophysiology, DOI: 10.1016/j. pathophys.2010.11.001). Whether these studies translate to humans has yet to be determined. Andy Coghlan n