Decades of research have highlighted the amygdala’s role in fear behavior. In this report, Feinstein and colleagues found that inhalation of 35% CO2 evoked not only fear, but also panic attacks, in three rare patients with bilateral amygdala damage. They suggest that an intact amygdala is not always required for fear and panic, and make an important distinction between fear triggered by external threats from the environment versus fear triggered internally by CO2.
Feinstein JS, Buzza C, Hurlemann R, Follmer RL, Dahdaleh NS, Coryell WH, Welsh MJ, Tranel D and Wemmie JA: Fear and panic in humans with bilateral amygdala damage. Nature Neuroscience 16: 270–272 (2013), doi:10.1038/nn.3323 .