Hjernens udvikling
The research suggests that it is not size alone that gives more brain power, but that, during evolution, increasingly sophisticated molecular processing of nerve impulses allowed development of animals with more complex behaviours.
I artiklen Origins of the brain: Complex synapses drove brain evolution bliver vi fortalt om en forståelse af hvordan vores hjerne har udviklet sig og hvilke elementer der gør at hjerneaktivitet har den komplekse virke, som den har
Current thinking suggests that the protein components of nerve connections – called synapses – are similar in most animals from humble worms to humans and that it is increase in the number of synapses in larger animals that allows more sophisticated thought.
“Our simple view that ‘more nerves’ is sufficient to explain ‘more brain power’ is simply not supported by our study,” explained Professor Seth Grant, Head of the Genes to Cognition Programme at the Wellcome Trust Sanger Institute and leader of the project. “Although many studies have looked at the number of neurons, none has looked at the molecular composition of neuron connections. We found dramatic differences in the numbers of proteins in the neuron connections between different species”.
Forsøget indikere at synapsernes virke og opbygning har en væsentligt rolle i forhold til udviklingen af hjernen og dens funktion. Og at det således ikke alene afhænger af størrelsen på hjernen i helhed.
“We studied around 600 proteins that are found in mammalian synapses and were surprised to find that only 50 percent of these are also found in invertebrate synapses, and about 25 percent are in single-cell animals, which obviously don’t have a brain.”
Synapses are the junctions between nerves where electrical signals from one cell are transferred through a series of biochemical switches to the next. However, synapses are not simply soldered joints, but mini-processors that give the nervous systems the property of learning and memory.
Remarkably, the study shows that some of the proteins involved in synapse signalling and learning and memory are found in yeast, where they act to respond to signals from their environment, such as stress due to limited food or temperature change.
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Simple invertebrate species have a set of simple forms of learning powered by molecularly simple synapses, and the complex mammalian species show a wider range of types of learning powered by molecularly very complex synapses.“It is amazing how a process of Darwinian evolution by tinkering and improvement has generated, from a collection of sensory proteins in yeast, the complex synapse of mammals associated with learning and cognition,” said Dr Richard Emes, Lecturer in Bioinformatics at Keele University, and joint first author on the paper.
The new findings will be important in understanding normal functioning of the human brain and will be directly relevant to disease studies. Professor Grant’s team have identified recently evolved genes involved in impaired human cognition and modelled those deficits in the mouse.
“This work leads to a new and simple model for understanding the origins and diversity of brains and behaviour in all species” says Professor Grant, adding that “we are one step closer to understanding the logic behind the complexity of human brains”
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