The human brain may be the most complex object in the universe, but its construction mostly depends on one thing: the shape of neurons.
Different kinds of neuron are selective about which other neurons they connect to and where they attach. Specific signalling chemicals are thought to be vital in guiding this process.
Henry Markram of the Swiss Federal Institute of Technology in Lausanne and colleagues built 3D computer models of the rat somatosensory cortex, each containing a random mix of cell types found in rat brains, but no signalling chemicals. Nevertheless, 74 per cent of the connections ended up in the correct place, merely by allowing the cells to develop into their normal shape.
The results suggest that much of the brain could be mapped without incorporating signalling chemicals. This is good news for neuroscientists struggling to map the brain’s dizzying web of connections. “It would otherwise take decades to map each synapse in the brain,” says Markram.
The work could also help untangle the causes of conditions like schizophrenia that are thought to be caused by flaws in brain wiring. If Markram’s work proves correct, malformed neurons that don’t connect up properly could be a factor.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1202128109
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