Swiss researchers have created a digital representation of a section of a brain of a juvenile rat to better understand the functioning of brain circuitry.
Consisting of 31,000 virtual neurons, 55 layers of cells and 207 different neuron subtypes, the digital brain will allow the researchers to study the activity of neurons and map connections between them.
Part of the Blue Brain Project overseen by the Ecole Polytechnique Federale de Lausanne (EPFL), the digital brain took ten years to develop. The result has been presented in the latest issue of the journal Cell.
"The reconstruction required an enormous number of experiments," said Henry Markram, who led the EPFL team. "It paves the way for predicting the location, numbers, and even the amount of ion currents flowing through all 40 million synapses."
Using powerful supercomputers, the researchers simulated actual processes in the digital brain, a slice of neocortex – an area of the brain responsible for sight and hearing in mammals.
They found that subtle changes in parameters, such the level of calcium ions, can produce changes across the brain circuits that could not be predicted based on the features of individual neurons.
For instance, slow synchronous waves of neuronal activity, which have been observed in the brain during sleep, were triggered in their simulations, suggesting that neural circuits may be able to switch into different ‘states’ that could underlie important behaviors.
"An analogy would be a computer processor that can reconfigure to focus on certain tasks," Markram explained. "The experiments suggest the existence of a spectrum of states, so this raises new types of questions, such as 'what if you're stuck in the wrong state?'"
For instance, Markram suggests that the findings may open up new avenues for explaining how initiating the fight-or-flight response through the adrenocorticotropic hormone yields tunnel vision and aggression.