EARLY LIFE ENVIRONMENTAL STRESS EFFECTS ON ADULT BEHAVIOR AND BRAIN MORPHOLOGY IN ZEBRA FINCHES

Abstract

Early developmental stress can influence brain development and ultimately shape behavioral variation in humans and other animals. While laboratory studies have repeatedly shown that exposure to developmental stressors affects brain morphology and behavioral variation across vertebrates, these studies often use direct application of severe stressors in experimental contexts to induce a response. Less well known is how naturally occurring environmental stressors impact brain and behavioral development and whether distinct stressors have distinct impacts. On the one hand, offspring development may be well buffered from natural environmental stressors, limiting their impact on behavioral traits. On the other hand, natural stressors during development may serve as cues to offspring of environmental conditions and induce changes that enable them to perform better in challenging environments later in life. In the latter case, impacts on behavior might be tuned to specific stressors. We investigate these possibilities in a semi-natural outdoor colony of the zebra finches (Taeniopygia guttata). We assessed individual exposure to three distinct environmental stressors during development, measured activity, aggression and anxiety-related behaviors in adulthood, and used magnetic resonance imaging (MRI) to investigate the impact of stressors on structural variation in regions of the brain associated with these behaviors. Overall, we found that early life environmental stressors impacted the development of brain and behavior, with particularly strong effects on aspects of fearfulness. However, individual stressors impacted behaviors differently, suggesting that, rather than generally inhibiting normal brain development, the natural stressors assessed here may instead act as cues of environmental conditions that individuals will experience later in life.