A group of researchers has developed a way for artificial neuronal networks to communicate with biological neuronal networks. The new development is a big step forward for neuroprosthetic devices, which replace damaged neurons with artificial neuronal circuitry.
The new method relies on the conversion of artificial electrical spiking signals to a visual pattern. That is then used, via optogenetic stimulation, in order to entrain the biological neurons.
The article titled “Toward neuroprosthetic real-time communication from in silico to biological neuronal network via patterned optogenetic stimulation” was published in Scientific Reports.
An international team led by Ikerbasque Researcher Paolo Bonifazi from Biocruces Health Research Institute in Bilbao, Spain, set out to create neuroprosthetic technology. He was joined by Timothée Levi from Institute of Industrial Science, The University of Tokyo.
One of the biggest challenges surrounding this technology is that neurons in the brain are extremely precise when communicating. When it comes to electrical neural networks, electrical output is not capable of targeting specific neurons.
To get around this, the team of researchers converted the electrical signals to light.
According to Levi, “advances in optogenetic technology allowed us to precisely target neurons in a very small area of our biological neuronal network.”
Optogenetics is a technology that relies on the light-sensitive proteins that are found in algae and other animals. When these proteins are inserted into neurons, light can be shined onto a neuron to make it active or inactive, depending on the type of protein.
The researchers used specific proteins that were activated by blue light in the project. The first step was to convert the electrical output of the spiking neuronal network into a checkered pattern made up of blue and black squares. This pattern was then projected by light down onto a 0.8 by 0.8 mm square of the biological neural network, which was growing in a dish. When this happened, only the neurons hit by the light coming from the blue squares were activated.
Synchronous activity is produced in cultured neurons whenever there is spontaneous activity. This results in a type of rhythm that is based on the way the neurons are connected together, the different types of neurons, and how they adapt and change.
“The key to our success,” says Levi, “was understanding that the rhythms of the artificial neurons had to match those of the real neurons. Once we were able to do this, the biological network was able to respond to the “melodies” sent by the artificial one. Preliminary results obtained during the European Brainbow project, help us to design these biomimetic artificial neurons.”
The researchers eventually found the best match after the artificial neural network was tuned to different rhythms, and they were able to identify changes in the global rhythms of the biological network.
“Incorporating optogenetics into the system is an advance towards practicality,” says Levi. “It will allow future biomimetic devices to communicate with specific types of neurons or within specific neuronal circuits.”
The future prosthetic devices that are developed with the system could replace damaged brain circuits. They could also restore communication between different regions of the brain. All of this could lead to an extremely impressive generation of neuroprosthesis.