Fear of Predators Suppresses Neurogenesis in the Brains of Wild Songbirds

TL;DR

Fear of predators can suppress brain cell growth in wild birds, suggesting lasting memories of fear may have evolutionary benefits.

Contribution

This study shows predator-induced fear suppresses neurogenesis in wild songbirds, revealing potential sex differences and adaptive memory retention.

Findings

Males showed suppressed hippocampal cell proliferation after predator cue exposure.

Both sexes had reduced immature neurons in the avian amygdala.

Enduring memory of fear may have adaptive evolutionary value in wild animals.

Abstract

Fear of predation can lead to behavioral changes indicative of an enduring memory of fear, as acknowledged by both ecologists and biomedical scientists studying post-traumatic stress disorder (PTSD). Enduring memories are often linked to suppressed neurogenesis in laboratory rodents as a potential mechanism to prevent the replacement of existing memories. We used predator vocalizations to assess the enduring effects of fear on neurogenesis in a wild songbird, black-capped chickadees (Poecile atricapillus), quantifying cell proliferation (PCNA immunoreactivity), and immature neurons (doublecortin immunoreactivity) in both sexes. Seven days after predator cue exposure, we found suppression of hippocampal cell proliferation in males, with no effect in females, and suppression of immature neurons in the avian amygdala (medial ventral arcopallium) in both sexes. Our results are consistent with the hypothesis that animals retained an enduring memory of fear, with potential sex differences in the behavioral and ecological consequences of these enduring neuronal changes. Finding effects indicative of an enduring memory of fear in wild caught animals supports the notion that there may be evolutionarily adaptive value to retaining an enduring, PTSD-like memory.

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