Article summary of Early-life stress has persistent effects on amygdala function and development in mice and humans by Cohen et al. - Chapter

Introduction

Relatively little is known about neurobiological changes caused by stressors during childhood, even though it is associated with an increased risk of developing psychopathology in later life. A widely used method to investigate the risks of stressors in childhood is to study children who were adopted from orphanages. However, these studies cannot indicate whether the results found are only associated with the upbringing in orphanages or if they have to do with prenatal factors. Little is also known about the long-term effects of stressors during childhood. The current study looks at a rodent model of stressors in childhood. The outcome measurements are in line with the human paradigm, and are therefore generalizable to human behavior.

Many animal studies have focused on the effects of stress in adulthood or the consequences of childhood stressors in adult life. Adult stressors have been shown to reduce PFC (prefrontal cortex) and hippocampal dendritic complexity and volume, but this is effect is reversible. Childhood stressors lead to problems in hippocampal dependent memory in adulthood and inconsistency in anxious behavior.

Method

This study looked at the type of stressor and its timing. To compare mice to humans (who had been adopted from orphanages), mice were used that were still drinking milk from the mother. To create "an orphanage situation", nesting opportunities were kept to a minimum and the mother was interrupted in her care practices. The anxiety response was measured when the mice reached preadolescent, adolescent, and adult age. Two hypothesis have been formed based on previous literature. The first hypothesis is that the childhood stressor would affect the regulation of anxiety (which is measured as the ability to suppress anxiety in order to achieve a goal). The second hypothesis is that this behavior is parallel to an increased activity of the amygdala.

Results

A go-no-go task was used to measure the suppression of anxiety. The analysis show that childhood stressors influence the ability to suppress anxiety responses in order to perform targeted behavior and that these effects persist into adulthood. To measure neural activity, the basolateral amygdala and the c-fos gene were examined. This gene is associated with anxiety-related systems. The results showed that there were stronger responses in mice who were exposed to childhood stressors. These results are generalizable to humans.

Discussion

The results are therefore in line with previous research and show that disorganized interrupted care in orphanages influences emotional and behavioral regulation in humans which persist into adulthood.The type of stressor experienced and its timing (in what period of one's life) also affect the outcome. Chronic stressors at an early age have stronger effects than short stressors later in life. These effects remain even after the stressor is gone.