Evolution of cognition might be down to brain chemistry
20:00 28 March 2011 by Andy Coghlan
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.
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."
Glutamate is the "brain's main energy metabolite", he says. "And as the main excitatory neurotransmitter it is responsible for virtually every possible cognitive task, including learning and memory."
David Kingsley of Stanford University in California was not involved in the study, but his team recently revealed genetic differences accounting for humans' larger brains. "It's clear that humans have accumulated some interesting differences in the thinking regions of the brain," he says. "It will be interesting to see how such differences arise from changes in our genomes and those of our closest relatives."
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