Non-gray circles and their connections represent 80, 70 and 60 percent (from top to bottom) of all outgoing traffic within the sampled section of a cortical region. Credit: Indiana University
70% of all info within cortical regions in the brain passes through only 20% of its regions’ neurons. These high-traffic “hub neurons” could play a role in understanding brain health since this sort of highly efficient network – in which a small number of neurons are more essential to brain function – is also more vulnerable to disruption. That’s because relatively small breakages can cause the whole system to “go down”. If the higher metabolic rates of hub neurons make them more vulnerable, for example, the resulting damage could be particularly harmful in conditions in which neurons are known to die, such as Alzheimer’s disease.
The existence of neurons that carry the majority of information between cortical regions in the brain has been previously reported by Prof Olaf Sporns…. But the new study is the first to show that a similar dynamic exists in communication within cortical regions, or the “micro-structures,” of the brain. It is also the first to measure activity across a particularly large number of neurons in these regions.
METHOD: IU scientists recorded small electrical impulses from up to 500 neurons from the somatosensory cortex – responsible for the sense of touch – measuring a surprisingly large volume of traffic across a relatively small area. As a collaboration across the fields of physics, informatics, neuroscience, and psychological and brain sciences, they were able to reveal the flow of both outgoing and incoming information within the living neural network by combining data from extremely high-resolution imaging technology with complex biophysical computer simulations of the brain.
“This is the first study to combine such a large number of neurons with such high temporal resolution,” Nigam said. “As a result, we can actually detect the direction of the communication flowing between neurons, creating a ‘transportation map’ from the connections within the cortex.” The experiments, conducted in live and tissue samples, were based in rodents. But similar high-traffic zones in the cortex have been shown to exist in more advanced mammals, including primates and adult humans.
Nigam added that understanding how the brain maintains good “air traffic control” between information-rich and information-poor neurons will be the next step in unraveling the mystery of hub neurons. “If we ever want to understand how these types of neurons keep information in our heads flowing smoothly,” he said, “we really need to learn a lot more about how they work together.”
http://news.indiana.edu/releases/iu/2016/01/hub-neurons.shtml
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