Neuroscientists at the Salk Institute have identified a small brain region next to the amygdala that may explain why fear responses outlast the threat that triggered them. Working in mice, the team focused on the amygdalostriatal transition zone, or ASt, which sits between the basolateral and central parts of the amygdala. Its neurons fired both strongly and for a sustained period, in contrast to amygdala neurons, which fire only briefly when danger first appears. The work was published in Neuron on September 14, 2026.
That timing mismatch has been a puzzle in fear research. Survival depends on a brain that scans for danger and stays alert until the danger passes, yet defensive behaviors like fight, flight, and freeze persist well beyond the short burst of amygdala activity that starts them. The Salk findings suggest the ASt may be what carries the response forward once the amygdala's initial alarm has quieted.
As the researchers put it, the amygdala has long been treated as the fear center while the space between its basolateral and central divisions was ignored entirely. Their question was what sustains fear after that first moment of firing - and the ASt is their candidate answer.
The practical interest here is in fear and panic disorders, where defensive responses become excessive or fail to switch off. A circuit that specifically maintains a fear state, rather than initiating it, would be a different kind of therapeutic target. This is animal research mapping basic circuitry, funded by private philanthropy and grants from the National Institutes of Health, so any treatment application remains a long way off.