That title is incorrect. These researchers did not stimulate one neuron to activate one memory. They stimulated a group of neurons in one region using a fiber optic.
I'll go through the experiment for those who don't really get the write up. Quick background:
0. Neurons are specialized cells in your brain, their firing is the basis of cognition. Neurons that fire strongly together tend to get linked. Not all your neurons are firing all at once. Not all neurons participate in a memory, but a large collection (0.1-4% depending on brain region) are used for each memory. (at least in naive mice) Memories are highly distributed across brain regions and within brain regions.
1. There is a gene 'cFos' that turns on in neurons that undergo activity. It is very short lasting, about an hour, and then it is back down. It is very cell specific, only cells used have been activated will show this gene.
2. There is a genetically inducable protein you can put in cells so that when you shine them with light they will start firing.
3. Anything genetically inducible can have a tag added that will make it impossible to induce when an animal is on a specific drug. (We'll call it Dox.)
The researchers made it so that when cFos is activated, it will transcribe the inducible light activated channel. But, it will only do this when the animal isn't on Dox. So they took the animal off Dox, exposed it to fear conditioning (they shocked it in a unique box), then put it back on Dox. So only the cells that were active during the fear conditioning will be turn on when they shine light.
They then put the animal in a new box and shined light, and the animal froze. (A sign it was afraid) They concluded that activating cells that had been active during the storing of the memory can 'reactivate' the memory, even out of it's context.
Of course there are a few major problems with this. The region of the brain they worked in is a relatively minor area of the brain. They admit in the course of the paper that each cell is used to store many memories. (They claim the assembly of cells activate the memory? But they never bother testing this.) Their firing pattern is far from physiological. The mice who underwent this 'memory reactivation' did not freeze as much as mice in normal fear conditioning and did not seem to learn the 'reactivated memory' at all. (Though again they didn't really bother testing this.) Normal fear-memory is learned quite well. This is a very preliminary but very important study in the field. It will be interesting to see how they follow this up.
Also, the Npas4 stuff is completely irrelevant to this article. There are countless markers that when 'knocked out' make it impossible to store memory.
I'll go through the experiment for those who don't really get the write up. Quick background:
0. Neurons are specialized cells in your brain, their firing is the basis of cognition. Neurons that fire strongly together tend to get linked. Not all your neurons are firing all at once. Not all neurons participate in a memory, but a large collection (0.1-4% depending on brain region) are used for each memory. (at least in naive mice) Memories are highly distributed across brain regions and within brain regions.
1. There is a gene 'cFos' that turns on in neurons that undergo activity. It is very short lasting, about an hour, and then it is back down. It is very cell specific, only cells used have been activated will show this gene.
2. There is a genetically inducable protein you can put in cells so that when you shine them with light they will start firing.
3. Anything genetically inducible can have a tag added that will make it impossible to induce when an animal is on a specific drug. (We'll call it Dox.)
The researchers made it so that when cFos is activated, it will transcribe the inducible light activated channel. But, it will only do this when the animal isn't on Dox. So they took the animal off Dox, exposed it to fear conditioning (they shocked it in a unique box), then put it back on Dox. So only the cells that were active during the fear conditioning will be turn on when they shine light.
They then put the animal in a new box and shined light, and the animal froze. (A sign it was afraid) They concluded that activating cells that had been active during the storing of the memory can 'reactivate' the memory, even out of it's context.
Of course there are a few major problems with this. The region of the brain they worked in is a relatively minor area of the brain. They admit in the course of the paper that each cell is used to store many memories. (They claim the assembly of cells activate the memory? But they never bother testing this.) Their firing pattern is far from physiological. The mice who underwent this 'memory reactivation' did not freeze as much as mice in normal fear conditioning and did not seem to learn the 'reactivated memory' at all. (Though again they didn't really bother testing this.) Normal fear-memory is learned quite well. This is a very preliminary but very important study in the field. It will be interesting to see how they follow this up.
Also, the Npas4 stuff is completely irrelevant to this article. There are countless markers that when 'knocked out' make it impossible to store memory.
Also here is a (paywalled) link to the paper:http://www.nature.com/nature/journal/vnfv/ncurrent/full/natu...
Here is a link to another (paywalled) paper which came out today which did almost the same thing and say almost opposite results (the details explain this oddity): http://www.sciencemag.org/content/335/6075/1513.full?rss=1
Here is a (paywalled) more layperson write up to the second article: http://www.sciencemag.org/content/335/6075/1455.full