The term “Optogenetics” was coined in 2006 by Karl Deisseroth. It refers to a method of probing and controlling genetically targeted neurons in vivo.
In simpler words researchers found a way to control neuronal firing by genetically engineering them to carry light sensitive Proteins from algae and archaebacteria (Opsins).
All brain cells are coded/enveloped by a membrane that has proteins (Ion-channels) in them that govern the flow of ions, the proteins from the microorganisms are analogues to ion channels, just light sensitive ones.
The algae (Chlamydomonas reinhardtii) : Light sensitive proteins that lets positive ions through in response to blue light (neural code for ON)
Archaebacteria (Natronomonas pharaonis) : Light sensitive proteins that lets negative ions through in response to yellow light (Neural code for OFF)
The proteins are encoded by genes (ChR2 and NphR) and the researchers could then take the genes and put them in neurons.
The genes are delivered via a viral vector (Lenti virus) to the specific neurons they want to control and they can then drive the neuron firing at the synapse level in response to light coming from a fiber-optical cable.
If the genes are coupled with an fluorescent protein, they can make whole neurons/neural circuits light up on activation!
…more to come