City living and urban upbringing affect neural social stress processing in humans

Urban and rural brains respond differently to stressOver the years, a number of studies have found that city living increases the risk of certain mental health problems, such as mood and anxiety disorders, and is thought to be linked to stresses in the urban social environment. In this study, Lederbogen and colleagues placed 32 healthy German volunteers from urban areas, towns, and rural areas under stress and used functional magnetic-resonance imaging (fMRI) to scan their brains and examine their neural processes. In addition to examining where participants currently live (city, town, or country), researchers also assessed where participants grew up along the country to city spectrum. In analyzing the data, Lederbogen and colleagues found that urban and country residents' brains handled the stress from the experiment differently in that different parts of their brains were activated. Researchers discovered that people living in the country had the lowest levels of activity in their amygdalas, structures responsible for processing and memory of emotional reactions such as environmental threats, while people living in towns had higher levels, and people living in the city had the highest levels of activity in their amygdalas. In addition, Lederbogen and colleagues discovered that whether people grew up in the city or country differentially impacted their perigenual anterior cingulate cortex (pACC), structures in the brain that helps regulate the amygdalas. Researchers found that people who spent more time growing up in the city had a more active pACC under stress, regardless of where they currently live. Lederbogen and colleagues conducted two other similar experiments, one using a different stress test and the other using a different sample of participants, and found the same results. In addition, researchers examined the functional connectivity between the pACC and amygdalas and found that urban upbringing was associated with reduced connectivity, while current urban living had no impact, highlighting the importance of early urban exposure on brain processes.