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Signature of consciousness captured in brain scans
IN BRIEF
TSUNEO YAMASHITA/TAXI JAPAN/GETTY
EVEN at the tender age of 3, children who later go on to be convicted of a crime are less likely to learn to link fear with a certain noise than those who don’t. This may mean that an insensitivity to fear could be a driving force behind criminal behaviour. Adult criminals tend to be fearless, but whether this characteristic emerges before or after they commit a crime wasn’t clear, says Adrian Raine, a psychologist at the University of Pennsylvania in Philadelphia. To find out, his team turned to data from a study in the 1970s which measured the sweat response of about 1800 3-year-olds in Mauritius when they were exposed to two different sounds. One sound was always followed by a noisy blare, the other by nothing. The children learned to anticipate which sound preceded the blare, and sweated in response to it – an indicator of fear. Decades later, the team looked to see if any of the subjects had criminal records and found that 137 did. Raine’s team discovered that these people had sweated significantly less in anticipation of the blare compared with subjects of similar race, gender and background for whom no criminal record was found (American Journal of Psychiatry, DOI: 10.1176/app1. ajp.2009.09040499).
18 | NewScientist | 21 November 2009
Conscious perception leaves its mark on brain scans A SIGNATURE pattern of brain activity has been found that could help determine whether braindamaged patients are conscious. A team led by Aaron Schurger of Princeton University reasoned that repeatedly presenting the brain with the same sensory input should evoke similar neural activity each time – if the input is processed consciously. If it does not enter consciousness, activity should vary because other subconscious processes will be running at the same time. To see if this could be used
to disentangle conscious from unconscious brain processes, the researchers asked 12 volunteers to look at images of faces and houses. The volunteers were shown either normal images, or versions of the same images presented as “invisible stimuli”, to evoke unconscious processing. The invisible images are formed by two drawings, one shown to each eye. In each pair, one drawing is in orange on a green background, while in the other the colours are reversed. Confronted with such contradictory inputs, the brain
reconciles them by creating a yellow patch. So while the brain has subconsciously processed the face or house, the volunteer consciously sees nothing but yellow. A set of functional magnetic resonance imaging recordings of the temporal lobes during both tasks backed up the researchers’ hypothesis: brain activity was similar each time a volunteer consciously looked at the same face or house, but invisible stimuli evoked a more variable response (Science, DOI: 10.1126/science.1180029). S. CHATTERJEE/J.M. CORDES/PALOMAR OBSERVATORY
Fearlessness may be linked to crime
Earth’s cosy blanket under a feeble sun SOME 2.5 billion years ago, the sun was so faint the oceans should have been ice. They weren’t, and this “faint young sun paradox” has puzzled scientists for decades. Now a modelling study suggests the answer lies with well-known greenhouse gases aided by an extra helping of nitrogen. Previous modelling attempts to resolve the paradox by loading the early atmosphere with greenhouse gases assumed that it has always had the same amount of nitrogen. But Colin Goldblatt of NASA Ames Research Center in California ran a model in which the pressure of nitrogen was twice what it is today. Nitrogen is not a greenhouse gas, but the increased pressure would have led to more frequent collisions between nitrogen molecules and greenhouse gases, causing them to absorb at more infrared wavelengths. Goldblatt found that this would have raised global temperatures by 4.4 °C (Nature Geoscience, DOI: 10.1038/ ngeo692). He admits that this doesn’t close the temperature gap entirely, but it could be part of the answer. Goldblatt says he has evidence that the crust and mantle have since absorbed the extra nitrogen.
Try ‘Stairway to Heaven’ on this bad boy IT’S the biggest guitar in the galaxy. The Guitar pulsar is a stellar corpse that is tearing through interstellar gas and creating a guitar-shaped wake of hot hydrogen (pictured). Its birthplace may now have been found. Little is known about the origins of such wayward stellar remnants. To hunt for the pulsar’s birthplace, Nina Tetzlaff at the University of Jena in Germany and colleagues projected the paths of 140 nearby groups of stars backwards in time over 5 million years. Previous work suggests the star was ejected at over 1500 kilometres per second. The team says the
pulsar’s path indicates that 800,000 years ago it was fired from a cluster of massive stars that now lies about 6500 light years away from Earth (Monthly Notices of the Royal Astronomical Society, vol 400, p L99). It’s a puzzle why the pulsar is moving so fast. Speeds greater than 1000 kilometres per second are hard to account for with current astronomy models, says James Cordes of Cornell University in Ithaca, New York. The object’s distance is not known for sure, he points out, which could mean the pulsar’s speed and its position have been misjudged.
TSUNEO YAMASHITA/TAXI JAPAN/GETTY
EVEN at the tender age of 3, children who later go on to be convicted of a crime are less likely to learn to link fear with a certain noise than those who don’t. This may mean that an insensitivity to fear could be a driving force behind criminal behaviour. Adult criminals tend to be fearless, but whether this characteristic emerges before or after they commit a crime wasn’t clear, says Adrian Raine, a psychologist at the University of Pennsylvania in Philadelphia. To find out, his team turned to data from a study in the 1970s which measured the sweat response of about 1800 3-year-olds in Mauritius when they were exposed to two different sounds. One sound was always followed by a noisy blare, the other by nothing. The children learned to anticipate which sound preceded the blare, and sweated in response to it – an indicator of fear. Decades later, the team looked to see if any of the subjects had criminal records and found that 137 did. Raine’s team discovered that these people had sweated significantly less in anticipation of the blare compared with subjects of similar race, gender and background for whom no criminal record was found (American Journal of Psychiatry, DOI: 10.1176/app1. ajp.2009.09040499).
18 | NewScientist | 21 November 2009
Conscious perception leaves its mark on brain scans A SIGNATURE pattern of brain activity has been found that could help determine whether braindamaged patients are conscious. A team led by Aaron Schurger of Princeton University reasoned that repeatedly presenting the brain with the same sensory input should evoke similar neural activity each time – if the input is processed consciously. If it does not enter consciousness, activity should vary because other subconscious processes will be running at the same time. To see if this could be used
to disentangle conscious from unconscious brain processes, the researchers asked 12 volunteers to look at images of faces and houses. The volunteers were shown either normal images, or versions of the same images presented as “invisible stimuli”, to evoke unconscious processing. The invisible images are formed by two drawings, one shown to each eye. In each pair, one drawing is in orange on a green background, while in the other the colours are reversed. Confronted with such contradictory inputs, the brain
reconciles them by creating a yellow patch. So while the brain has subconsciously processed the face or house, the volunteer consciously sees nothing but yellow. A set of functional magnetic resonance imaging recordings of the temporal lobes during both tasks backed up the researchers’ hypothesis: brain activity was similar each time a volunteer consciously looked at the same face or house, but invisible stimuli evoked a more variable response (Science, DOI: 10.1126/science.1180029). S. CHATTERJEE/J.M. CORDES/PALOMAR OBSERVATORY
Fearlessness may be linked to crime
Earth’s cosy blanket under a feeble sun SOME 2.5 billion years ago, the sun was so faint the oceans should have been ice. They weren’t, and this “faint young sun paradox” has puzzled scientists for decades. Now a modelling study suggests the answer lies with well-known greenhouse gases aided by an extra helping of nitrogen. Previous modelling attempts to resolve the paradox by loading the early atmosphere with greenhouse gases assumed that it has always had the same amount of nitrogen. But Colin Goldblatt of NASA Ames Research Center in California ran a model in which the pressure of nitrogen was twice what it is today. Nitrogen is not a greenhouse gas, but the increased pressure would have led to more frequent collisions between nitrogen molecules and greenhouse gases, causing them to absorb at more infrared wavelengths. Goldblatt found that this would have raised global temperatures by 4.4 °C (Nature Geoscience, DOI: 10.1038/ ngeo692). He admits that this doesn’t close the temperature gap entirely, but it could be part of the answer. Goldblatt says he has evidence that the crust and mantle have since absorbed the extra nitrogen.
Try ‘Stairway to Heaven’ on this bad boy IT’S the biggest guitar in the galaxy. The Guitar pulsar is a stellar corpse that is tearing through interstellar gas and creating a guitar-shaped wake of hot hydrogen (pictured). Its birthplace may now have been found. Little is known about the origins of such wayward stellar remnants. To hunt for the pulsar’s birthplace, Nina Tetzlaff at the University of Jena in Germany and colleagues projected the paths of 140 nearby groups of stars backwards in time over 5 million years. Previous work suggests the star was ejected at over 1500 kilometres per second. The team says the
pulsar’s path indicates that 800,000 years ago it was fired from a cluster of massive stars that now lies about 6500 light years away from Earth (Monthly Notices of the Royal Astronomical Society, vol 400, p L99). It’s a puzzle why the pulsar is moving so fast. Speeds greater than 1000 kilometres per second are hard to account for with current astronomy models, says James Cordes of Cornell University in Ithaca, New York. The object’s distance is not known for sure, he points out, which could mean the pulsar’s speed and its position have been misjudged.