Controlling the Brain with Light and Lasers
An Introduction to Optogenetics
In 2005, scientists created a technique called optogenetics, where light is used to control neuron activity in the brain. Since then, optogenetics became super popular in neuroscience labs for studying the brain and the interactions neurons have with each other.
But outside the realm of neuroscience, no one really knows about it (a tragedy, in my opinion).
But I’m here to change that. By the end of this article, you’ll have a better understanding of what optogenetics is and why it’s important.
The Brain 🧠
What even happens up there?
The brain is the most complex part of the human body. It controls all your bodies’ functions, interprets information, and embodies your mind. Our brain rules our intelligence, beliefs, emotions and creativity. Simply put, we are who we are because of the brain.
This biological wonder consists of three main parts: the cerebrum (this consists of the 4 lobes), cerebellum and the brainstem.
Beyond this, there are 10¹⁵ connections in the brain, which is around 100 billion. Just to put that in perspective: that’s roughly the same number of stars in the Milky Way Galaxy.
Fun fact: We have less than 1% of the human connectome completely mapped right now (connectome: the map of all the neural connections in the brain)
For more on the human connectome, click here!
Optogenetics studies how different parts of the brain interact with each other, so it’s really important to understand the magnitude of neurons and connections we’re working with.
Nervous System ⚡
Your nervous system is what transmits signals through the body and the brain. This system is made up of neurons (approximately 86 BILLION) that consist of an axon, dendrite, and a cell body.
Your brain gets signals because of communication between neurons through a process called synaptic transmission. Information is transmitted through electric impulses called “action potential” that travel down the axon to the axon terminal. In these axon terminals are synaptic vesicles that contain neurotransmitters: chemical messengers of the brain. Once the impulse reaches the synaptic vesicles, they release necessary neurotransmitters that carry the action potential across the synapse to the dendrites of the next neuron.
Optogenetics studies the transmission of signals from neuron to neuron to understand how neurons communicate with each other.
Optics 🔦
Optics is the branch of physics that deals with the behaviour and properties of light (visible, infrared and ultraviolet).
Enter, Optogenetics 🔬
Finally, we get to the cool stuff.
Like I mentioned at the very beginning of the article, optogenetics is a technique where light and genetic engineering are used to control neuron activity.
But, why is optogenetics important?
First and foremost, it’s super cool. But on a more serious note, optogenetics enables scientists to study the interaction of neurons on a much, much, deeper scale. The brain is almost all unexplored territory and the list of how much we don’t know heavily outweighs the list of how much we do.
I talked about neuron communication through synaptic transmission earlier, but as it turns out, not all neurons communicate in the same way! That’s just one of the big gaps in our knowledge of the brain — we don’t fully understand how neurons communicate with each other.
Still, it’s responsible for making us who we are, and that’s why it’s so important to understand it.
To learn more about how much we don’t know about the brain, click here.
How does it work? 📝
First, neurons are genetically modified by the insertion of a new piece of code to express photo-sensitive proteins called opsins. Opsins are super powerful “switches” that can be activated/deactivated by light. They were first discovered in algae, including channelrhodopsin-2(ChR2), the opsin most commonly used for optogenetic experiments.
Scientists found a way to inject the ChR2 protein into a virus.
Quick note: The way viruses spread is by putting their genetic information into a cell and giving the cell instructions to replicate the virus.
Along the membrane of a neuron are ion channels. These channels are proteins that let certain ions enter or exit the neuron. When a neuron is activated (normally by neuron depolarization), ion channels open and signals can be transmitted.
When the (harmless) ChR2 virus is injected into a part of the brain, the ChR2 gene is converted into a protein through transcription and translation. The opsins then hijack these ion channels and get expressed in that section of the brain.
If you don’t know about genetic transcription and translation, here’s a video to help you out!
After this, the brain ready to be controlled. Scientists use photon lasers, computers and fibre optics to precisely control neural circuits with impeccable timing.
What we can do with optogenetics 🔍
So far, optogenetics has opened many new avenues down which we can venture. Because of its insane precision, optogenetics is super valuable in detecting which exact sections of the brain light up during different activities. This is helpful in endeavours to map out the brain and to understand the neurological implications of many diseases.
Currently, experiments have been mainly on mice, but even by only experimenting on non-human subjects, we’ve been able to cure epilepsy and symptoms of Parkinson’s, restore sight, treat hearing loss, and summon memories.
And even more good news: virtually any disease or activity that involves the brain can be understood and solved with optogenetics.
Here are a few resources to learn more about breakthroughs in optogenetics:
- New advances in optogenetics a key step towards the treatment of neurological disorders
- Optogenetics in Cellular Biology and Human Disease Models
- Steve Ramirez and Xu Liu: A mouse. A laser beam. A manipulated memory.
Key Takeaways 🔑
- Optogenetics is the use of genetic engineering and optics in order to control neural circuits
- Opsins (photo-sensitive proteins) get injected in the brain and expressed in neural circuits after genetic transcription and translation
- When light hits the encoded proteins, parts of the brain can be turned on and off
- So far, optogenetics has found treatment or cures to epilepsy, Parkinson’s, blindness, etc.
- Optogenetics can cure basically any disease that affects the brain!
