Memory Control

Scientists can now turn a particular memory “on” and “off” by controlling the specific neurons that help encode it, a new study reports.

Thanks to cutting-edge technology that allows researchers to control individual brain cells, a team has found a way to activate and deactivate memories of certain environments in mouse brains.

The past few years have brought some major breakthroughs in our understanding of how memory works – and in our ability to control it. For instance, we now know that memories aren’t stored in any specific location in the brain, but in interconnections among many regions. We’ve also learned that each time we recall a memory, our brains alter its details and “save” it anew; in other words – as Jorge Luis Borges famously wrote almost a century ago – all our memories are actually memories of memories.

This discovery has led to some astounding new technologies that can target specific memories and alter their content – or even download new memories directly into our brains. This field is still in its infancy – it’ll be a few more years before doctors can start opening up “Eternal Sunshine” clinics – but there’s no question that our children will grow up in a world where brains are as hackable as computers are today.

And a team led by Mark Mayford at the Scripps Research Institute has taken a historic step down that path, the journal Science reports. The team got their hands on some mice that had been genetically engineered to produce neurons that respond to artificial chemical triggers; and they introduced the little guys to some new colors, smells and textures in a box they called Box A.

Thanks to the fluorescent neurons of these special mice, the researchers were able to see exactly which neurons in their tiny rodent brains leaped into action when they formed a memory of a new experience (the team focused mainly on the hippocampus, basolateral amygdala, and cerebral cortex, all of which are known to play important roles in memory formation and recall).

You better stay out of our heads, mad scientists!

Now, here’s where things went Full Mad Scientist: the team moved the mice into a second box, Box B, and “turned on” the neurons associated with the mice’s memories of Box A.

What happened in the mice’s brains was extraordinary – they adapted to these strange circumstances by forming hybrid memories of Box A and Box B:

When an ensemble of neurons for one context (ctxA) was artificially activated during conditioning in a distinct second context (ctxB), mice formed a hybrid memory representation.

And when the mice were put in Box B without having their Box A memories artificially turned on, they didn’t seem to recognize the place at all. In other words, their “recognition” behavior in Box B was completely dependent on the researchers’ artificial activation of their Box A memories:

Reactivation of the artificially stimulated network within the conditioning context was required for retrieval of the memory, and the memory was specific for the spatial pattern of neurons artificially activated during learning.

This suggests something fascinating: memories don’t seem to be stored in distinct “files” in the brain at all – they seem to grow from existing knowledge patterns, like new branches on a tree. And that’s great news for scientists hoping to develop treatments for disorders like schizophrenia and PTSD, because it means we can learn to artificially disable aspects of a memory – such as certain emotional associations – without deleting its content.

The more we learn about the inner lives of our brains, the clearer it becomes that they work very differently from computers – or from any digital medium, for that matter. Just as weirder and weirder creatures keep turning up in the deep sea, our brains seem to get stranger and more mysterious the more we study them.

Which begs the question, How much more do scientists still need to learn before you’d feel safe letting them tweak your cerebral settings?

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