American Scientist

Neuroscientist Ahmad Hariri explains how the watchdog of the brain—the amygdala—is overactive in those with depression and anxiety.

A Sleep of Reason Produces Monsters from Jagmeet Mac on Vimeo.

Ahmad Hariri is a neuroscientist at Duke University studying the brain activity underlying depression and anxiety. Even though depression and anxiety can manifest in a variety of ways, people experiencing such disorders share a striking commonality that Hariri is working to understand. An excerpt of Hariri’s explanation from the video above:

The amygdala is a structure that exists in every animal with a backbone, and it exists as essentially the same structure in all of those animals, too. And for all of us, from reptiles to birds to amphibians to mammals, the amygdala serves to detect changes in the environment. So, we study it often in the context of helping us prepare and respond to threat. [Like a watchdog,] it notices something and it starts to bark. And then it’s the job of the prefrontal cortex to say, “OK, I hear you, amygdala. You’ve noticed something and you’ve woken me up. I’m going to figure out what it is.” And, the prefrontal cortex is what allows you to look more carefully ahead of you and decide: Is that a stick or branch, or is it a snake that could bite me and maybe even be fatal?

That’s the give-and-take of the amygdala and the prefrontal cortex. Without the amygdala, you kind of blunder over that object. And if it’s a snake, you’re bit, and you probably don’t go on to have many more days like that. Evolutionarily speaking, the amygdala helps us survive. And it exists in all of these creatures because of that role. But at the same time, you don’t want to stop at every stick and every snake and be frozen without any idea of how best to respond. That’s where the prefrontal cortex comes in. It provides regulation.

There’s a famous Spanish painter that I admire named Francisco Goya. One of his famous etchings is The Sleep of Reason Produces Monsters. I think it’s a very nice way to think of it: When the prefrontal cortex is no longer doing its job of listening to the amygdala, acknowledging that signal, and then regulating it, we get all of the problems that we think of as depression, anxiety, and PTSD. There are natural differences between individuals in their capacity to both regulate emotions as well as in their general tendency to respond strongly with emotion.

When I talk about measuring amygdala reactivity or even prefrontal cortex activity, it’s all through this functional MRI, or fMRI, technique. We’re bringing as many scientific tools and technologies to bear on the question of what makes us who we are and how we react to our worlds.