Inception for Mice


They used a conditional expression system  to express a light activated channel specifically in cells thought to be involved in fear memories (the dentate gyrus or CA1). When a mouse explores a new area, neurons involved in remembering that area begin to express this light activated channel.

First, they let a mouse explore a new area and the light activated channel accumulates in the neurons dedicated to remembering that space. The next day they perform a fear conditioning protocol where in a new space, the mice are exposed to foot shocks. While they are performing this training, they are also using a fiber optic cable to shine light into the mouse’s brain to turn on the light activated channels that had accumulated in the neurons dedicated to remembering the first day’s environment. After this training when the mice are placed in a third novel environment, they have their usual amount of trepidation in exploring a new place. When the mice are returned to the environment they were placed into on the first day (just to explore), they were significantly more afraid.

What this suggests, is that when those neurons dedicated to remembering the first space were activated during the foot shock training protocol, the mouse associated the foot shocks with the first environment. Effectively, now they remember being shocked in a place where they were never shocked. This would be the “implanting” of a new memory into the mouse’s brain.

This is pretty interesting in conjunction with some things I’ve heard about how our memory works. Each time you retrieve a memory from your subconscious it becomes malleable and new associations can be made such that the memory can actually change over a lifetime. So if for example, you were walking along thinking about your grandma’s delicious waffles and you were suddenly struck by a car, perhaps your brain could make a painful association with grandma’s waffles.

So unlike Inception, the mice aren’t asleep when the “new memory” is added. And unlike Inception, I think I actually understand what the heck happened to these mice.


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