Researchers at the University of Iowa studied three women whose amygdalae on both sides of the brain had been destroyed by a rare genetic disease, one of whom had famously shown no fear of snakes or haunted houses, and had them breathe air mixed with extra carbon dioxide.
All three women experienced sudden panic attacks when they inhaled the carbon dioxide mixture, with rapid breathing and a genuine sense of suffocation and terror. Only 3 of 12 healthy comparison participants panicked under the same test.
The result split fear into two systems: one triggered from outside the body, by a snake or a haunted house, governed by the amygdala, and one triggered from inside the body, by a signal like rising carbon dioxide, running through a separate pathway that needs no amygdala at all. The finding rests on only three patients with this rare condition, striking but drawn from a very small group.
Read the original study
Feinstein et al., Nature Neuroscience, 2013 · doi.org/10.1038/nn.3323
No amygdala, and panic anyway.
Source
- Feinstein, J. S., Buzza, C., Hurlemann, R., Follmer, R. L., Dahdaleh, N. S., Coryell, W. H., Welsh, M. J., Tranel, D., & Wemmie, J. A. (2013). Fear and panic in humans with bilateral amygdala damage. Nature Neuroscience, 16(3), 270–2. https://doi.org/10.1038/nn.3323