OPTOGENETICS

Controlling the Brain by Shining Light

Do you think that one day we can upload or download our memory? Is it possible to control behaviours and emotions of others? Have you ever imagined that memory can be unreliable?

BY ARMIN NAJARPOUR FOROUSHANI

ARMIN NAJARPOUR FOROUSHANI IS A PHD CANDIDATE IN BIOMEDICAL ENGINEERING AT POLYTECHNIQUE SCHOOL OF MONTREAL.

ARMIN NAJARPOUR FOROUSHANI IS A PHD CANDIDATE IN BIOMEDICAL ENGINEERING AT POLYTECHNIQUE SCHOOL OF MONTREAL.

In 2005, Karl Deisseroth’s laboratory at Stanford including graduate students Ed Boyden and Feng Zhang (both now professor at MIT) invented a method to stimulate particular population of neurons in the brain selectively using light. This method was called optogenetics [1].

The idea was taken from the nature: It was known that algae swims on the water away from light because of having a kind of light-sensitive ion channel on their cell membrane called channelrhodopsin2.

It was like a spark to produce the same ion channels on neurons. So, they did a genetic engineering trick. They extracted algae protein (gene) and connected it to another piece of DNA called promoter and put this sequence in a virus and injected the virus into the mouse brain. When the virus goes into the brain it infects neurons that activate the promoter and in those cells the algae protein activates cells (For the first try they used mouse cultured hippocampal cells). By doing this procedure, light sensitive ion channels (channelrhodopsin2) were created on neuron cells of certain region of the brain. Then it was shown that blue light can stimulate channelrhodopsin2 and each light pulse produces a single spike with high precision. Later it was shown that another type of light-sensitive ion channel (halorhodopsin) can be created on the neurons and silent them when the yellow light shines on those genetically engineered cells. So, using channelrhodopsin2 and halorhodopsin and by applying blue and yellow light it is possible to activate and silent neurons. In this way different brain functions can be controlled by activating and deactivating neurons associated for that function.

It was shown that using optogenetic on particular genetically engineered region of mouse brain can produce running behaviour on a circle. Another application was controlling anxiety and fear conditioning in the mouse brain. By stimulating channelrhodopsin-expressed cell bodies in basolateral amygdale (BLA) using blue light they could produce high level of freezing in mouse and by stimulating axons of certain part of amygdale they could reduce the level of anxiety in mouse [2].

In 2010, optogenetics was selected by Nature Methods as the method of the year [3]. In 2013, researchers at MIT created false memory in mouse hippocampus using optogenetics. In this experiment the mouse had fear about something that never experienced and was not naturally conditioned (classical conditioning) to any neutral stimulus [4].

So, in this way we can control the brain and mind using light. Imagine a society with no mental disorder. Optogenetics is one step toward that dream. Technology cannot be bad or good, this is human decision that defines it.


References: 

[1] Boyden, Edward S., et al. "Millisecond-timescale, genetically targeted optical control of neural activity." Nature neuroscience 8.9 (2005): 1263-1268.

[2] Tye, Kay M., et al. "Amygdala circuitry mediating reversible and bidirectional control of anxiety." Nature 471.7338 (2011): 358-362.

[3] Deisseroth, Karl. "Optogenetics." Nature methods 8.1 (2011): 26-29.

[4] Ramirez, Steve, et al. "Creating a false memory in the hippocampus."Science 341.6144 (2013): 387-391.