Optogenetics: A Breakthrough to Understanding Our Brains
The human brain is one of the most complex systems on Earth. The brain stores approximately 86 billion neurons. These neurons make up an elaborate system that forms our movements, behaviors, and habits. Although we have learned a lot about the human brain in the last decade, we still know very little. However, a new field of study called optogenetics allows us to learn more. Optogenetics is the use of light to control neuron pathways. This is made possible with the combination of neuroscience and the science of light. Let me explain more in the following paragraph:
So How does Optogenetics work?
First of all, we have to take a quick trip back to high school Biology:
For our brains to send signals, neurons, the information messenger cells of our body, have to communicate. Information in our bodies is stored in electrical signals. These electrical signals travel through our neurons: down the dendrites, across the axon, then through synapses to get into the next neuron.
Many neurons make up a neuron pathway. Neuron pathways are responsible for our movements, behaviors, and habits.
Information traveling in our bodies is much like a telephone game where a line of people takes turns whispering a message to the next one in line. Now imagine each person in the telephone game is a neuron and the whispered message is the electrical signal. That is pretty much how neurons work in our brain. The line of people is like a neuron pathway. But the only difference is that neurons are better communicators than us and the message doesn’t get distorted when traveling.
For a neuron to start sending signals, it requires neurotransmitters to open ion channels in the plasma membrane of the neuron. After the ion channel opens, an action potential occurs and a signal is sent to the connecting neuron. Ion channels are like locked on-off switches for signal sending. Neurotransmitters are like keys that open ion channels and start signal sending.
As the name implies, optogenetics requires optics, the study of light, and the study of genetics. In optogenetics, light replaces neurotransmitters in firing neurons. For this to work, we have to make neurons respond to light by taking genes from organisms that use photosynthesis. Genes from these organisms contain proteins called opsins. Opsins create electrical signals that can open ion channels in response to light. Afterward, genes responsible for creaking opsins are placed into neurons using gene theory. This works by having viruses house the gene and then injecting the virus into the animal’s brains.
Currently, the most popular opsin is channelrhodopsin-2(ChR2), which comes from Chlamydomonas reinhardtii, a kind of green algae. Neurons with ChR2 would react only when blue light is shined on them.
Optogenetics is better than electrical stimulation when studying brains because with the use of optogenetics only chosen neurons fire without interfering with neighboring neurons. Optogenetics is also faster than the use of pharmaceuticals since when using optogenetics it takes as fast as a millisecond for it to activate to silence neurons. Optogenetics is a more effective technique in studying brains than preexisting ones.
That’s cool! So how is it used now?
Optogenetics is currently used mostly on mice since there are still many complications with using optogenetics on humans.
The first written in vivo(in a living organism) optogenetics study was in 2007. This study was on the relationship between orexin‐producing neurons and waking up from sleep. Before this study, it was unclear whether the relationship between orexin‐producing neurons and waking up from sleep was correlative, causal, or have any relationship at all. In this study, scientists used optical fiber, a flexible transparent fiber that can transmit light signals, to flash blue light on ChR2-expressing orexin‐producing neurons. After this experiment, they found that orexin‐producing neurons do have a causal relationship with arousal from sleep.
In addition to learning about the function of specific neurons, optogenetics allows us to also learn more about mental health. For example, optogenetics can help us identify what causes depression chemically. According to Medical News, the development of methods with optogenetics can help scientists study the ventral tegmental area (VTA) of the brain which is responsible for development, motivation, and reward. Optogenetics allows for scientists to study the neuron circuits responsible for symptoms of anhedonia, the lack of pleasure. New knowledge about this brain region can help scientists come up with better treatments for depression. Optogenetics is also doing to same for other mental disorders like schizophrenia, Alzheimer’s disease, Parkinson’s disease, and obsessive-compulsive disorder.
Optogenetic will revolutionize mental health research and neuron function and much more. Optogenetics brings us a step closer to knowing more about the fascinating science of our brains!
