Optogenetics involves tweaking the genes of neurons so that they become sensitive to light. By combining this technique with genetic and viral approaches, researchers can insert these channels into very specific populations of neurons. Ultimately, this approach allows researchers to control distinct groups of neurons and individual circuits of the brain by stimulating them with light-emitting devices inserted into the brain. First, researchers inject the subject with a genetically engineered virus, designed to infect brain tissue. These viruses aren’t harmful and have been engineered by scientists to deliver a benign DNA strand that code for special surface proteins, which respond to specific wavelengths of light. These single-celled organisms produce a protein called channelrhodopsin that makes them sensitive to sunlight.
At present, optogenetics can be used only on animals whose brain functions associated with elemental emotions, like fear and anxiety and reward, are similar to those in humans. Early tests have been successful in mice and primates to restore sight in blind test animals. Optogenetics was a major spur to the Obama Administration’s announcement, in 2013, of the BRAIN Initiative, a $300 million program for developing technologies to treat such neurological ailments as Alzheimer’s disease, autism, schizophrenia, and traumatic brain injury. It is possible that optogenetics could be used as a therapeutic tool in humans. Some clinicians are already looking at possible treatments in the peripheral nervous system
Optogenetics has given researchers unprecedented access to the workings of the brain, allowing them not only to observe its precise neural circuitry in lab animals but to control behavior through the direct manipulation of specific cells. The aim is to gain an understanding of brain functions such as attention, memory, social skills and emotions. For instance, a person diagnosed with schizophrenia displays cognitive impairment, which may hinder the performance of day-to-day tasks, such as showing up to work or the ability to make decisions. The challenge is to understand how the brain performs cognitive processes in the first place and how this is changed in psychiatric disorders. Several new studies have shown the potential of optogenetic stimulation to rapidly modify depression and anxiety related behaviors in animal models. It is potentially more effective and has fewer adverse effects than classic light therapy or pharmacological approaches to treat mental illness.
Circuit-level understanding of psychiatric symptoms is allowing more sophisticated pathophysiological hypotheses, which is important for replacing the current system of subjective report-based measures. Second, by combining patient interviews and personalized genomics, diagnoses of mental illnesses are well poised to change substantially in a manner that could improve both prevention and treatment. Third, direct knowledge of cells that are involved in psychiatric symptoms is facilitating identification of clinically relevant circuit biomarkers, which could revolutionize not only diagnosis but also prediction of treatment outcomes. It’s too early to say that optogenetics could inform the treatment in humans. But the research could enact changes on our models of mental illness.
Albert, P.R. (2014). Light up your life: Optogenetics for depression? Journal of PsychiatryNeuroscience 39, 3-5.
Colapinto, J. (2015, May 18). Lighting the Brain. The New Yorker. Retrieved from http://www.newyorker.com/magazine/2015/05/18/lighting-the-brain
Myers, A. (2012, November 18). Optogenetics illuminates pathways of motivation through brain, study shows. Stanford Medicine. Retrieved from https://med.stanford.edu/news/all-news/2012/11/optogenetics-illuminates-pathways-of-motivation-through-brain-study-shows.html
Jonathan Torres, M.S.
WKPIC Doctoral Intern
[Director’s Note: No, Dr. Greene, you may not go back to the rat lab just because this is interesting. Seriously. No.]