When you’re scared, do you find yourself frozen stiff or trying to escape?
Scientists at the European Molecular Biology Laboratory and GlaxoSmithKline say they’ve uncovered the neural switch that regulates between an active or a passive response to fear. Those researchers conditioned mice to associate a particular sound with a nasty electronic shock, so that the mice would be scared when they heard the sound. Then, by selectively inhibiting certain neurons in the central nucleus of the amygdala — a brain region known to control fear — the researchers were able to stop frightened mice from freezing when the sound was played. Instead, the animals would display more active coping strategies: digging or rearing, for example. Brain imaging techniques revealed that this switch also was associated with increased brain activity in the cortex.
This research, which appears in the journal Neuron, helps us to understand the neural underpinnings of fear — and may help us to understand why different people respond in different ways when they’re frightened.
“When we inhibited these neurons, I was not surprised to see that the mice stopped freezing because that is what the amygdala was thought to do,” researcher Cornelius Gross said in a statement about his work. It’s well-known that the amygdala makes mice (and people) scared or not scared. But it was not well-known that this brain region might control how mammals act scared. “It seemed that we were not blocking the fear, but just changing [the mice's] responses from a passive to an active coping strategy,” Gross said. —By Laura Blue