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Brain's bouncer filters out distractions
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This week–
Brain’s gatekeeper caught in action ALISON MOTLUK
IF YOU’RE reading this on a train, while making a mental note of the shopping you need, watching for your stop and trying to ignore the motormouth in the seat to your left, your “working memory” is in full swing: it’s the mental space we use for dealing with the here and now, and it’s strongly linked to intelligence scores. Now a study claims to have found the parts of the brain responsible for deciding just what you let into your mental workspace – and what you ignore. Working memory enables most people to pay attention to only three or four things at a time. One theory is that it is finite, and that some people simply have more available than others. Another is that a good working memory is distinguished from a poor one by the ability to filter out irrelevant stuff and focus on the pertinent information. In other words, some people just have more trouble ignoring distractors (see “Focus, focus, focus”, page 30). This idea is backed up by a 2005 study in
Reprogrammed adult mouse cells reverse disease FOR the dream of personalised medicine using reprogrammed adult cells, it is an important proof of principle. Skin cells taken from mice with a form of sickle-cell anaemia have been reprogrammed back into an embryonic-like state, “corrected” so that they no longer produce defective proteins, and used to reverse the symptoms of the disease. The breakthrough is exciting 12 | NewScientist | 15 December 2007
which participants were asked to remember only red items shown on a screen, when blue items were being shown as well. They found that the better the volunteers were at ignoring the blue items, the better their working memory scores were, suggesting that an efficient working memory was related, at least in part, to the ability to stay focused and ignore irrelevant stimuli. Now the parts of the brain with this “gatekeeper” role have been pinpointed by Torkel Klingberg and Fiona McNab of the Karolinska Institute in Stockholm, Sweden. The pair used an fMRI scanner to measure the brain activity of 25 volunteers as they prepared to filter out irrelevancies. For example, they were told that if a triangle cue appeared on the screen, they should prepare to ignore any yellow circles that follow it and, conversely, if a square cue appeared, they should prepare to remember any yellow circles that follow. The researchers found that two regions of the brain were active as the volunteers prepared to filter this information. One was the
because it proves that reprogrammed adult cells – believed to be as versatile as stem cells obtained from a human embryo – could be used to cure disease in humans, provided researchers can find a way of reprogramming them safely. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, and his colleagues used a retrovirus to insert four genes into mouse skin cells, causing their development to run in reverse. They then used a precise form of gene “editing” called homologous recombination to pluck out the defective beta-globin gene responsible for sickle-cell
–Only the best information allowed in–
prefrontal cortex, which is known to be involved in a range of highlevel, executive control processes and is also linked to intelligence. The other was the globus pallidus, part of the brain involved in initiating and regulating motor commands and other actions. Klingberg says there was a positive association between the volunteers’ working memory (measured before the scans took place), the level of activity in the two brain areas during filtering,
and their scores in the filtering tasks (Nature Neuroscience, DOI: 10.1038/nn2024). “They have pretty compelling data,” says Edward Awh of the University of Oregon at Eugene. He likens the basal ganglia – of which the globus pallidus is a part – to the working memory’s own nightclub bouncer. “If you have an exclusive nightclub with limited capacity, then you’ll want to have someone good on the door,” he says. ●
anaemia and replace it with a correctly functioning version. Next, the researchers treated the corrected stem cells with growth factors to coax them into becoming blood stem cells, from which any type of blood cell can develop. These cells were injected back into the bone marrow of the mice, where they reversed the symptoms of sickle-cell anaemia within days (Science, DOI: 10.1126/science.1152092). “All improved
to almost normal,” says Jaenisch. “These mice are basically cured.” Obstacles remain before the technique could be used in humans, however. The reprogramming of adult cells currently relies on a retrovirus to insert the genes into the cells’ DNA, but there are concerns that it could insert the genes in the wrong place, leading them to cause cancer (see Interview, page 44). One of the genes, called c-Myc, is also a cancer-causing oncogene, although last week Shinya Yamanaka at Kyoto University, Japan, revealed the technique works just as well without it (Nature Biotechnology, DOI: 10.1038/nbt1374). Andy Coghlan ●
“The cells were injected back into the bone marrow of the mice, and reversed the symptoms of sickle-cell anaemia in days”
www.newscientist.com
This week–
Brain’s gatekeeper caught in action ALISON MOTLUK
IF YOU’RE reading this on a train, while making a mental note of the shopping you need, watching for your stop and trying to ignore the motormouth in the seat to your left, your “working memory” is in full swing: it’s the mental space we use for dealing with the here and now, and it’s strongly linked to intelligence scores. Now a study claims to have found the parts of the brain responsible for deciding just what you let into your mental workspace – and what you ignore. Working memory enables most people to pay attention to only three or four things at a time. One theory is that it is finite, and that some people simply have more available than others. Another is that a good working memory is distinguished from a poor one by the ability to filter out irrelevant stuff and focus on the pertinent information. In other words, some people just have more trouble ignoring distractors (see “Focus, focus, focus”, page 30). This idea is backed up by a 2005 study in
Reprogrammed adult mouse cells reverse disease FOR the dream of personalised medicine using reprogrammed adult cells, it is an important proof of principle. Skin cells taken from mice with a form of sickle-cell anaemia have been reprogrammed back into an embryonic-like state, “corrected” so that they no longer produce defective proteins, and used to reverse the symptoms of the disease. The breakthrough is exciting 12 | NewScientist | 15 December 2007
which participants were asked to remember only red items shown on a screen, when blue items were being shown as well. They found that the better the volunteers were at ignoring the blue items, the better their working memory scores were, suggesting that an efficient working memory was related, at least in part, to the ability to stay focused and ignore irrelevant stimuli. Now the parts of the brain with this “gatekeeper” role have been pinpointed by Torkel Klingberg and Fiona McNab of the Karolinska Institute in Stockholm, Sweden. The pair used an fMRI scanner to measure the brain activity of 25 volunteers as they prepared to filter out irrelevancies. For example, they were told that if a triangle cue appeared on the screen, they should prepare to ignore any yellow circles that follow it and, conversely, if a square cue appeared, they should prepare to remember any yellow circles that follow. The researchers found that two regions of the brain were active as the volunteers prepared to filter this information. One was the
because it proves that reprogrammed adult cells – believed to be as versatile as stem cells obtained from a human embryo – could be used to cure disease in humans, provided researchers can find a way of reprogramming them safely. Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, and his colleagues used a retrovirus to insert four genes into mouse skin cells, causing their development to run in reverse. They then used a precise form of gene “editing” called homologous recombination to pluck out the defective beta-globin gene responsible for sickle-cell
–Only the best information allowed in–
prefrontal cortex, which is known to be involved in a range of highlevel, executive control processes and is also linked to intelligence. The other was the globus pallidus, part of the brain involved in initiating and regulating motor commands and other actions. Klingberg says there was a positive association between the volunteers’ working memory (measured before the scans took place), the level of activity in the two brain areas during filtering,
and their scores in the filtering tasks (Nature Neuroscience, DOI: 10.1038/nn2024). “They have pretty compelling data,” says Edward Awh of the University of Oregon at Eugene. He likens the basal ganglia – of which the globus pallidus is a part – to the working memory’s own nightclub bouncer. “If you have an exclusive nightclub with limited capacity, then you’ll want to have someone good on the door,” he says. ●
anaemia and replace it with a correctly functioning version. Next, the researchers treated the corrected stem cells with growth factors to coax them into becoming blood stem cells, from which any type of blood cell can develop. These cells were injected back into the bone marrow of the mice, where they reversed the symptoms of sickle-cell anaemia within days (Science, DOI: 10.1126/science.1152092). “All improved
to almost normal,” says Jaenisch. “These mice are basically cured.” Obstacles remain before the technique could be used in humans, however. The reprogramming of adult cells currently relies on a retrovirus to insert the genes into the cells’ DNA, but there are concerns that it could insert the genes in the wrong place, leading them to cause cancer (see Interview, page 44). One of the genes, called c-Myc, is also a cancer-causing oncogene, although last week Shinya Yamanaka at Kyoto University, Japan, revealed the technique works just as well without it (Nature Biotechnology, DOI: 10.1038/nbt1374). Andy Coghlan ●
“The cells were injected back into the bone marrow of the mice, and reversed the symptoms of sickle-cell anaemia in days”
www.newscientist.com