Anxiety disorders are common and can strongly affect daily life. People with anxiety often face an inner conflict: should I go for something rewarding, or avoid it because it feels scary or risky? In this thesis, I investigated how serotonin – an important brain chemical – influences this kind of decision-making. We developed a semi-natural experiment in which rats had to collect food while facing a potential threat. This allowed us to study how they balance reward and safety. We then changed the serotonin system, either with a widely used antidepressant (fluoxetine) or through genetic modifications. Our findings show that serotonin affects how cautiously or quickly decisions are made under stress. Higher serotonin levels slowed down decision-making, while very low levels led to faster, less fearful behavior. These results improve our understanding of why some individuals are more vulnerable to anxiety and how anxiety treatments work in the brain.
Xianzong Meng (Alex Meng, 孟宪宗; born 5 August 1993) earned dual bachelor’s degrees in Laboratory Medicine (Dalian Medical University) and Biomedical Science (Curtin University). After completing an honours program and working on serotonin research using HPLC-MS, he began his PhD at the Donders Institute in 2019, studying serotonin’s role in risky foraging behavior in rats.