In an ongoing effort to traumatise mice and then erase their bad memories, scientists have gone towards the light. I don't know what I'm saying. Here's Lisa Winter at IFLScience with a better explanation:

For sufferers of PTSD, bad memories can severely interrupt day-to-day life; episodic memories of specific places, people, or events can trigger insurmountable fear. Scientists though have found a way to target specific memories in mice and erase them using light, making it conceivable that conditions like PTSD might be thing of the past one day. Additionally, they proved a 40-year-old theory about how episodic memories are stored and retrieved in the brain.

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While it's not likely that this will be used to create an Eternal Sunshine of the Spotless Mind-like memory eraser, verifying how memories are stored and retrieved could open up possibilities for treatments for those experiencing memory loss or PTSD at some point down the road. (Source)

Thanks to Cristian for this one!

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