Flashbulb memories are intensely vivid memories, so-called because they are like photographs "flashed" into our minds, usually linked with emotionally charged events. But what makes these memories so clear and detailed? This is where our friend the amygdala, an almond-shaped structure deep in our brain, comes into play.

Just imagine a situation where 24 people were asked to remember what they did on a typical summer day in 2001, and also the horrific events of 9/11. The catch? They did all this while lying inside a big donut-like MRI machine, which captures images of brain activity. Some of these participants were in downtown Manhattan, just a stone's throw from the World Trade Center, while others were a few miles away in Midtown during the attacks.

Now, what happened when they remembered 9/11? The Downtown Manhattan group's amygdalae (that's the plural for amygdala!) lit up like a Christmas tree on the scanner, but not when they recalled their average summer days. In fact, 83% of these folks showed higher activity in their left amygdala when thinking about 9/11 than the summer day. But what about the Midtown group? Their brains were a bit more chill; only 40% of them showed that increased amygdala action. And when they remembered the summer events? Both groups were the same, no crazy light shows in the amygdala.

Interestingly, the closer the participant was to Ground Zero during the attacks, the more their amygdala fired up when remembering 9/11 (correlation of 0.45, which is quite significant).