Researchers at the University of California, Los Angeles have discovered that chronic stress significantly alters brain activity in the amygdala, impairing decision-making and increasing habitual behaviors.

The study reveals that chronic stress reduces the capacity for deliberate decision-making while enhancing automatic, habitual responses in the brain.

These findings underscore the necessity for further research in humans to confirm the effects of stress on behavior and decision-making processes.

Led by neuroscientist Jacqueline Giovanniello, the research was inspired by her own experiences with stress during her university years.

In experiments, mice were subjected to mild stressors such as damp bedding and white noise to simulate chronic stress conditions.

The stressed mice learned to press a lever for food rewards, but their decision-making was notably impaired compared to a control group of unstressed mice.

Behavioral tests indicated that while control mice adapted their lever-pressing behavior based on reward value, stressed mice became insensitive to changes in reward, demonstrating a shift towards habitual actions.

When presented with an abundance of food, unstressed mice displayed flexible decision-making by refraining from pressing the lever, whereas stressed mice continued to press it frequently, highlighting their habitual behavior.

The research focuses on the roles of two brain circuits: the basolateral amygdala–dorsomedial striatum (BLA→DMS) and central amygdala–dorsomedial striatum (CeA→DMS), which are crucial in learning and habit formation.

After exposure to stress, the CeA→DMS projections became more active, further promoting habit formation among the stressed mice.

The study suggests that targeting these specific brain circuits could provide therapeutic strategies for addressing stress-related compulsive behaviors.

Published in Nature, the study titled 'A dual-pathway architecture for stress to disrupt agency and promote habit' details the biological mechanisms by which stress favors routine behaviors over thoughtful decision-making.