Simulating Neurons to Understand Where Brain Waves Originate
Scientists from the Blue Brain Project at Ecole polytechnique fédérale de Lausanne in Switzerland, are using a complex computer model as a new tool to solve the mystery of how billions of interconnected neurons work together to produce brain waves.
The brain has many different types of neurons, all carrying electrical signals. Exactly what is it about the structure and function of each and every neuron, and the way they network together, that give rise to these electrical signals measured in a human brain?
The Blue Brain Project is aimed at modeling a complete human brain. Currently, the team studies rodent brain tissue and characterizes different types of neurons to exacting detail, including their electrical properties, shapes, sizes, and how they connect.
The computer model draws on cellular biophysics and cognitive neuroscience. The two disciplines however, have different methods and scientific language.
Researchers want to bridge this gap via simulating electrical brain activity and relating the behavior of single neurons to brain waves, opening the way to better tools for diagnosing mental disorders, and on a deeper level, offering a better understanding of ourselves.
Unprecedented Brain Circuit Modeling
The work is based on a computer model of a neural circuit the sophistication of which has never been seen before, having an unparalleled amount of detail and simulating 12,000 neurons.
“It is the first time that a model of this complexity has been used to study the underlying properties of brain waves,” says Sean Hill of EPFL.
Researchers noticed that the electrical activity swirling through the entire simulated system was reminiscent of brain waves measured in rodents. Because the computer model uses an awesome amount of physical, chemical and biological data, the supercomputer simulation allows scientists to analyze brain waves at a level of detail simply unattainable with established monitoring of live brain tissue.
“We need a computer model because it is impossible to relate the electrical activity of potentially billions of individual neurons and the resulting brain waves at the same time,” explained Hill. “Through this view, we’re able to provide an interpretation, at the single-neuron level, of brain waves that are measured when tissue is actually probed in the lab.”
Ion Channel Behaviour and Brain Wave Shape
Like microscopic batteries, neurons need to be charged in order to fire off an electrical impulse known as a “spike”. Neurons communicate with each other through these “spikes” to produce thought and perception.
To “recharge” a neuron, charged particles called ions must travel through tiny ionic channels. These channels are like gates that regulate electrical current. In the end, the accumulation of multiple electrical signals throughout the entire circuit of neurons produces brain waves.
“Our model is still incomplete, but the electrical signals produced by the computer simulation and what was actually measured in the rat brain have some striking similarities,” says scientist Costas Anastassiou of the Allen Institute for Brain Science. “For the first time, we show that the complex behavior of ion channels on the branches of the neurons contributes to the shape of brain waves.”
Much work remains in order to reach a complete simulation. While the model’s electrical signals are comparable to in vivo measurements, researchers say that there are still many open questions as well as room to improve the model. For instance, the simulation is modeled on neurons that control the hind-limb, while in vivo data represent brain waves coming from neurons that have a similar function but control whiskers instead.
Even so, the computer model we used allowed us to characterize, and more importantly quantify, key features of how neurons produce these signals,” says Anastassiou.