This post is by guest blogger Matthew Savage
Are you a fan of sci-fi? Do you feel that mind-control would be an amazing tool for humans to possess or do you believe it a power that should be left strictly for the X-men? Do you struggle with sleep and think it would be great to be able to sleep at the flick of a button? Or do you think the ability to turn off a negative emotion or change an unhappy memory would be an excellent tool? Well a scientific method called Optogenetics may just hold the key to all of the above and it is a scientific method that is thriving today. Simply put, Optogenetics uses a combination of genetic manipulation and optics to examine individual neurons which make up our brain (Kasparov, 2012). But this is not an easy task. The average human brain has around 86 billion neurons (Azevedo et al, 2009), specialised cells responsible for sending and receiving signals. These cells fire electrical currents down their axons and to gaps between the cells, known as synapses. Chemical changes then occur, and messengers cross the gap, delivering the desired message to the neighbouring cell. Through this complex communication process, our brains produce memories, emotions and behaviours (Fan, 2019). It is the examination of these billions of neurons that Optogenetics is focusing on and the clinical applications it offers potential for are extremely exciting and scary at the same time!
So, what is Optogenetics in a nutshell?
Optogenetics is “a method which uses light to modulate molecular events in a targeted manner in living cells or organisms” (Nature, 2020). It is a method that uses special proteins called opsins which are light-sensitive, originally discovered in the 1970s but their application was limited until the 21st century. In 2005, researchers announced that opsins had been introduced into rat brain cells and when a blue light was shone on to the cells, a spike in electrical activity was observed, creating a light sensitive brain cell.
However, this was an experiment that took place in a petri dish, so the next step was to demonstrate this technique in a live animal and in 2007, scientists undertook similar methods to modify cells in the motor cortex of a mouse. Once again, with the use of optic fibre blue light, scientists were able to make the mouse walk in circles, indicating how certain cell activity correlates with specific behaviour and motor movements. Since then, scientists have been able to put fruit flies to sleep on command, have taught mice to be fearful, to be sociable, to seek food and even to hallucinate an experience (Fan, 2019). Researchers have also claimed that optogenetics helped restore light sensitivity to cells in a mouse that had lost its vision and it is believed that clinical trials in human subjects may start soon. But recent focus has also been to develop wider uses for Optogenetics, including its use in curing neurodegenerative conditions, addiction, psychosis and other mental disorders.
So why is this important?
Optogenetics provides a whole array of possibilities. If we can turn a set of neuronal cells on, then we can figure out exactly how they contribute to behaviour, pinpointing exact cells which are contributing to a disease state (Boyden, 2013). In addition to this, if we can turn off cells which are causing a disease, we could potentially cure certain neurological diseases. More specific drugs could be created as we can aim light at individual cells and more specific treatments can occur, instead of treatments such as deep brain stimulation. For example, the effectiveness of many anti-depressants is often a cause for debate, with many studies noting efficacy levels of 28% (Sundaram, 2019). Optogenetics has noted changes in neuronal activity in the reward circuits of the brain of depressed individuals and it is this kind of understanding that is key to developing new treatments for depressive disorders. In addition to this, it is believed that optogenetics could soon help repair failing organs in a non-evasive way, including brain cells which are affected in neurodegeneration (Shevchenko, 2018).
What is the future of Optogenetics?
More sinister suggestions may be that these methods could be used eventually to control human behaviours and implant false emotions and experience in the human brain. It may even be possible to control people’s behaviours via such methods. However, for now, this scenario is still a long way off. At this moment, new technologies need to understand the principles of treating brain disorders, such as how specific cells contribute to these disorders and new modalities can be generated from increased understanding of the computations of the brain. Research may focus on finding cures for conditions whereby defective cells and neuronal circuits could be corrected. For example, research suggests that a lack of dopamine is a major contributor to Parkinson’s Disease, and when dopamine producing cells die, symptoms such as tremor, slowness, stiffness and balance problems occur. Parkinson’s disease therapy currently focuses on the alleviation of symptoms, but it is hoped, with the use of Optogenetics, it may be possible to reactivate defective dopamine producing cells to enhance therapeutic benefits and support a cure.
Optogenetics offers so many possibilities but it still must leap the hurdle of implementation in human subjects. Implanting genes to non-human primates has also proven to be far more of a challenge as implanting opsins into monkey neurons involves creating a hole in the monkeys’ skull and infecting the required cells with a virus. This virus also carries a “promotor” gene which restricts opsin expression in other cells and finding the right combination of virus and promotor is no easy task (Servick, 2020). Human and non-human primate brains are also far bigger and more complex than those of rodents and light therapy has been shown to be less effective due to dispersion. However, with neuroscience heavily focusing on single-cell behaviours and Optogenetics offering the ability to focus on individual neurons, so many things could be possible in the not too distant future. A future whereby scientists can implant experiences into our brains, insomniacs can sleep on command or where tiny optogenetic devices could be implanted into our bodies to provided targeted therapies may not be so far off!
About Matt Savage
Matthew Savage has an MSc in Psychology, is a qualified personal trainer, and has worked within the field of cognitive rehabilitation for 5 years. He is an FA qualified football coach, with a keen interest in moral behaviour and wellbeing within team sports. Matthew is also one of our Mental Health Triage Practitioners.
References
- Azevedo FA, et al. (2009) Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. J Comp Neurol 513:532–541
- Chen, Y., Xiong, M., & Zhang, S. C. (2015). Illuminating Parkinson's therapy with optogenetics. Nature biotechnology, 33(2), 149–150. https://doi.org/10.1038/nbt.3140
- Editor’s choice, Scientific Reports, (2020). Nature Editor's choice: optogenetics. Available at: https://www.nature.com/collections/rprjmxbnsg/ [accessed 10/01/2020]
- Fan, S., (2019). How Scientists Used Light to Incept Sensations and Memories in Mice. Available at: https://singularityhub.com/2019/07/23/how-scientists-used-light-to-incept-sensations-and-memories-in-mice/ [accessed 09/01/2020]
- Heusted, E., (2013). Explained: Optogenetics. Massachusetts Institute of Technology. Available at: https://www.youtube.com/watch?v=Nb07TLkJ3Ww [accessed 09/01/2021]
- Kasparov, S., (2012). Primer on the Autonomic Nervous System. Third Addition.
- Servick, K., (2020). Controlling monkey brains with light could get easier thanks to open data project. Available at: https://www.sciencemag.org/news/2020/10/controlling-monkey-brains-light-could-get-easier-thanks-open-data-project [accessed 11/01/2020]
- Sundaram, J., (2019). Optogenetics Applications. Available at: https://www.news-medical.net/life-sciences/Optogenetics-Applications.aspx [accessed 10/01/2020]