Optogenetics – Using Light to Watch Live Neuronal Transmission
Optogenetics is a relatively new neuroscience approach that combines genetics with the physics of light. It uses light to monitor and control neurons that have been genetically modified to sense and respond to light. Optogenetics allows neuroscientists to control and monitor the activities of individual neurons in living tissue – even within freely-moving animals – and to precisely measure the effects of those manipulations in real-time. Now, EPFL scientists have observed and measured synaptic transmission in a live animal for the first time.
This breakthrough work is published in Neuron with the title “In Vivo Measurement of Cell-Type-Specific Synaptic Connectivity and Synaptic Transmission in Layer 2/3 Mouse Barrel Cortex.” The open access paper can be freely downloaded.
Recording and Analyzing Synaptic Transmissions in the Mouse’s Brain
Optogenetics works by inserting the gene of a light-sensitive protein into live neurons, from a single cell to an entire family of them. The genetically modified neurons then produce the light-sensitive protein, which sits on their outside, the membrane. There, it acts as an electrical channel – something like a gate. When light is shone on the neuron, the channel opens up and allows electrical ions to flow into the cell; a bit like a battery being charged by a solar cell.
Then, it is possible to use light to precisely control the activity of specific neurons in living, even moving, animals in real time. Such precision is critical in being able to study the hundreds of different neuron types and understand higher brain functions such as thought, behavior, language, memory – or even mental disorders.
Aurélie Pala and Carl Petersen, researchers at EPFL’s Brain Mind Institute, used optogenetics to stimulate single neurons of anesthetized mice and see if this approach could be used to record synaptic transmissions. The targeted neurons were located in a part of the mouse’s brain called the barrel cortex, which processes sensory information from the mouse’s whiskers. When the researchers shone blue light on the neurons that contained the light-sensitive protein, the neurons activated and fired signals. The researchers recorded and analyzed synaptic transmissions in the mouse’s brain.
The mission of the EPFL’s Brain Mind Institute is to understand the fundamental principles of brain function in health and disease, by using and developing unique experimental, theoretical, technological and computational approaches. The Institute participates in the Blue Brain Project at EPFL and the Human Brain Project of the European Commission.
Aurélie Pala, who received her Ph.D. for this work, said:
This is a proof-of-concept study. Nonetheless, we think that we can use optogenetics to put together a larger picture of connectivity between other types of neurons in other areas of the brain.
In future studies, the researchers plan to extend these first in vivo measurements of cell-type-specific synaptic transmission to other well-defined neocortical cell types and to compare synaptic transmission across different behavioral states in awake mice.
In previous experiments in optogenetics research labs worldwide, researchers have been able to control the movements of laboratory animals and help them recovering from stroke. Today’s preliminary steps are still very far from science-fiction-like applications of optogenetics to mind reading and mind control, but research is advancing fast, and amazing applications involving optogenetics and other techniques are on the horizon. All seems to indicate that the next decade will see the beginning of a Golden Age of neurotechnology, with breathtaking implications. We may soon be able to drive our car by thought alone as foreseen by Nissan researchers and develop artificial telepathy between persons far away. Like today’s cell phones – but implanted in the brain.
Images from Stanford University and Shutterstock.