A classical lay summary by Roshni Shetty, from the University of California, Davis.
The article titled "Millisecond-timescale, genetically targeted optical control of neural activity" (Boyden et al. 2005) presents a ground-breaking technique called optogenetics, which allows scientists to control neural activity in the brain with extreme precision and speed. The approach involves introducing light sensitive proteins called opsins derived from microorganisms like algae and bacteria into neurons via genetic engineering. Opsins are like solar panels and when exposed to specific wavelengths of light, they have the ability to change the electrical activity of neurons. With this technique, scientists now have the power to turn specific neurons on and off. This can be advantageous since we can control a neuron, and actually see what it does.
Microorganisms producing light-gated proteins that regulate ion flow were discovered nearly 50 years ago. But it took scientists several years to bring this approach to neuroscience. The earliest study by Edward Boyden and Karl Deisseroth in 2005 (Boyden et al. 2005) introduced an opsin Channelrhodopsin-2 into neurons and demonstrated reliable, millisecond-timescale control of neuronal spiking. Since then, there have been exciting discoveries in understanding brain communication, neuronal circuits responsible in various functions and behaviour as well as understanding of diseases. For example, scientists have used optogenetics to identify the neural circuits that underlie specific behaviors, such as addiction, anger and memory. Optogenetics has also been used to study the neural basis of diseases such as Alzheimer's, with the hope of developing new treatments (Iaccarino et al. 2016). An amusing study by Dayu Lin and David Anderson (Lin et al. 2011) demonstrated that when they activated certain neurons previously known to be active when male mice fought using optogenetics, the mice would attack whatever was next to them, even a rubber glove!
The key advantage of this method compared to traditional methods such as electrical stimulation is that we can now selectively activate or inhibit specific neuronal populations or circuits in awake behaving animals.
Beyond neuroscience, optogenetics has applications in other fields including muscle, cardiac, immune cells, and embryonic stem cells. While optogenetics is still a relatively new field, it has the potential to revolutionize our understanding of the brain and other biological processes. As the technology continues to evolve, we can expect to see even more exciting breakthroughs in the years to come.
- Boyden, Edward S., Feng Zhang, Ernst Bamberg, Georg Nagel, and Karl Deisseroth. 2005. “Millisecond-Timescale, Genetically Targeted Optical Control of Neural Activity.” Nature Neuroscience 8 (9): 1263–68. https://doi.org/10.1038/nn1525.
- Iaccarino, Hannah F., Annabelle C. Singer, Anthony J. Martorell, Andrii Rudenko, Fan Gao, Tyler Z. Gillingham, Hansruedi Mathys, et al. 2016. “Gamma Frequency Entrainment Attenuates Amyloid Load and Modifies Microglia.” Nature 540 (7632): 230–35. https://doi.org/10.1038/nature20587.
- Lin, Dayu, Maureen P. Boyle, Piotr Dollar, Hyosang Lee, E. S. Lein, Pietro Perona, and David J. Anderson. 2011. “Functional Identification of an Aggression Locus in the Mouse Hypothalamus.” Nature 470 (7333): 221–26. https://doi.org/10.1038/nature09736.