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Evolution of cognition might be down to brain chemistry
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luke hayes/millennium images, UK
IF YOU have a fear of heights, you wouldn’t think being given extra stress hormone would help – yet Dominique de Quervain at the University of Basel, Switzerland, and colleagues report that it can. People with phobias are usually treated by exposing them to what they are frightened of. The idea is that if a phobia is learned, people can be desensitised by learning that there is in fact nothing to fear. Experiments on animals suggest that cortisol, a hormone made in response to stress, helps boost such relearning. To test whether it could help people combat phobia, de Quervain’s team gave cortisol to 40 people with a fear of heights before subjecting them to a desensitising programme of increasingly dizzying situations displayed via a virtual reality headset. They were also asked to walk up an outdoor, three-storey staircase. Three days later, those given cortisol felt significantly less fear of real and virtual heights as measured by standardised questionnaires and skin conductance tests. This difference was still apparent a month later (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1018214108). De Quervain suggests cortisol might help other conditions based on traumatic memories, such as post-traumatic stress disorder.
How the chemical food for human thought evolved THE molecules that fuel thinking and memory have evolved far more in human brains compared with other primates. Philipp Khaitovich of the Partner Institute for Computational Biology in Shanghai, China, and colleagues analysed brain tissue from deceased humans, chimpanzees and rhesus macaques to study the concentrations of 100 chemicals linked with metabolism. In the human prefrontal cortex, the levels of 24 of these were drastically different from levels in the corresponding brain regions
of the other primates. In the cerebellum, however, there were far fewer differences between humans and the other animals, with just six chemicals showing different concentrations. This suggests that, since our lineage split off from other primates, the evolution of metabolism in the thinking and learning parts of our brains has gone much further than in our “primitive” cerebellum (Proceedings of the National Academy of Sciences, DOI: 10. 1073/pnas.1019164108).
Khaitovich says the comparison confirms the key role played in human thought by glutamate, a chemical that energises brain cells and ferries messages between them. It was present at relatively low levels in humans, which he says is because it is used faster in energy-hungry human brains. “Brain metabolism probably played an important role in evolution of human cognition,” Khaitovich says, “and one of the potentially most important changes was in glutamate metabolism.” Chris Hellier/Corbis
Hormone calms fear of heights
Dye could slow brain’s ageing A COMMON dye used to identify the tangles of proteins that accompany ageing also helps to prevent protein misfolding – one of the hallmarks of Alzheimer’s disease. When Gordon Lithgow at the Buck Institute for Research on Aging in Novato, California, and colleagues grew the soil-dwelling nematode Caenorhabditis elegans in agar plates soaked in thioflavin T – a dye used to visualise clusters of amyloid beta protein – they found that the worms lived 30 to 70 per cent longer than average. Further investigation suggested that by binding to amyloid beta, the dye helps to preserve the environment that the proteins need to form complex threedimensional shapes. This may prevent the misfolding that accompanies ageing, which can lead to the formation of protein clumps seen in Alzheimer’s (Nature, DOI: 10.1038/nature09873). “People have been using these compounds for assays, but now we are showing they are also powerful biological agents,” says Lithgow. “We need to start thinking about compounds that target aggregation processes and protein misfolding pathways.”
The monkey that eats dinner twice WE HUMANS might have the gift of the gab, but only one primate can truly be said to chew the cud. Famous for their long noses, proboscis monkeys (Nasalis larvatus) live in the forests of Borneo. Ikki Matsuda of Kyoto University in Japan and colleagues made two trips there in recent years and were surprised to see the monkeys regurgitating food and chewing it again (Biology Letters, DOI: 10.1098/rsbl.2011.0197). The monkeys spent longer feeding on days when they regurgitated food, and Matsuda speculates that chewing the cud might help them to
clear large food particles from their foreguts, allowing them to eat more. Such large tree-living animals are confined to big branches so can only reach poorer-quality foliage. Being able to eat more could be crucial. The evidence is not totallly convincing, says Murray Logan of Monash University in Victoria, Australia, because Matsuda did not examine the monkeys’ mouths to confirm they contained food. But he knows from experience – he studies rumination in koalas – how difficult it is to do that. “I sympathise completely,” he says.
2 April 2011 | NewScientist | 19
luke hayes/millennium images, UK
IF YOU have a fear of heights, you wouldn’t think being given extra stress hormone would help – yet Dominique de Quervain at the University of Basel, Switzerland, and colleagues report that it can. People with phobias are usually treated by exposing them to what they are frightened of. The idea is that if a phobia is learned, people can be desensitised by learning that there is in fact nothing to fear. Experiments on animals suggest that cortisol, a hormone made in response to stress, helps boost such relearning. To test whether it could help people combat phobia, de Quervain’s team gave cortisol to 40 people with a fear of heights before subjecting them to a desensitising programme of increasingly dizzying situations displayed via a virtual reality headset. They were also asked to walk up an outdoor, three-storey staircase. Three days later, those given cortisol felt significantly less fear of real and virtual heights as measured by standardised questionnaires and skin conductance tests. This difference was still apparent a month later (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1018214108). De Quervain suggests cortisol might help other conditions based on traumatic memories, such as post-traumatic stress disorder.
How the chemical food for human thought evolved THE molecules that fuel thinking and memory have evolved far more in human brains compared with other primates. Philipp Khaitovich of the Partner Institute for Computational Biology in Shanghai, China, and colleagues analysed brain tissue from deceased humans, chimpanzees and rhesus macaques to study the concentrations of 100 chemicals linked with metabolism. In the human prefrontal cortex, the levels of 24 of these were drastically different from levels in the corresponding brain regions
of the other primates. In the cerebellum, however, there were far fewer differences between humans and the other animals, with just six chemicals showing different concentrations. This suggests that, since our lineage split off from other primates, the evolution of metabolism in the thinking and learning parts of our brains has gone much further than in our “primitive” cerebellum (Proceedings of the National Academy of Sciences, DOI: 10. 1073/pnas.1019164108).
Khaitovich says the comparison confirms the key role played in human thought by glutamate, a chemical that energises brain cells and ferries messages between them. It was present at relatively low levels in humans, which he says is because it is used faster in energy-hungry human brains. “Brain metabolism probably played an important role in evolution of human cognition,” Khaitovich says, “and one of the potentially most important changes was in glutamate metabolism.” Chris Hellier/Corbis
Hormone calms fear of heights
Dye could slow brain’s ageing A COMMON dye used to identify the tangles of proteins that accompany ageing also helps to prevent protein misfolding – one of the hallmarks of Alzheimer’s disease. When Gordon Lithgow at the Buck Institute for Research on Aging in Novato, California, and colleagues grew the soil-dwelling nematode Caenorhabditis elegans in agar plates soaked in thioflavin T – a dye used to visualise clusters of amyloid beta protein – they found that the worms lived 30 to 70 per cent longer than average. Further investigation suggested that by binding to amyloid beta, the dye helps to preserve the environment that the proteins need to form complex threedimensional shapes. This may prevent the misfolding that accompanies ageing, which can lead to the formation of protein clumps seen in Alzheimer’s (Nature, DOI: 10.1038/nature09873). “People have been using these compounds for assays, but now we are showing they are also powerful biological agents,” says Lithgow. “We need to start thinking about compounds that target aggregation processes and protein misfolding pathways.”
The monkey that eats dinner twice WE HUMANS might have the gift of the gab, but only one primate can truly be said to chew the cud. Famous for their long noses, proboscis monkeys (Nasalis larvatus) live in the forests of Borneo. Ikki Matsuda of Kyoto University in Japan and colleagues made two trips there in recent years and were surprised to see the monkeys regurgitating food and chewing it again (Biology Letters, DOI: 10.1098/rsbl.2011.0197). The monkeys spent longer feeding on days when they regurgitated food, and Matsuda speculates that chewing the cud might help them to
clear large food particles from their foreguts, allowing them to eat more. Such large tree-living animals are confined to big branches so can only reach poorer-quality foliage. Being able to eat more could be crucial. The evidence is not totallly convincing, says Murray Logan of Monash University in Victoria, Australia, because Matsuda did not examine the monkeys’ mouths to confirm they contained food. But he knows from experience – he studies rumination in koalas – how difficult it is to do that. “I sympathise completely,” he says.
2 April 2011 | NewScientist | 19