Abstract
Danger signals elicit an immediate behavioural response as well as a prolonged increase in sensitivity to threats. We investigated the alarm response in larval zebrafish to identify neural circuits underlying such transitions. 5-7 day old larvae react to the alarm substance (Schreckstoff) by increased intervals between swim bouts and extended immobility. Calcium imaging indicates that olfactory sensory neurons innervating a lateral glomerulus detect the substance. Several telencephalic regions including the entopeduncular nucleus are also activated, with sustained activity outlasting stimulus delivery observable in the lateral habenula, posterior tuberculum, superior raphe, locus coeruleus, and periaqueductal gray. Consistent with the idea that these changes are related to an increased sensitivity to threats, larvae show increased dark avoidance after Schreckstoff removal. These results demonstrate that danger cues activate multiple brain circuits resulting in the expression of a continuum of defensive behaviors, some of which extend beyond stimulus detection.
Competing Interest Statement
The authors have declared no competing interest.