Emotional Contagion Boosts Resilience Via Serotonin in Mice

"Bystander" mice that briefly watched other mice be harmed show fewer signs of behavioral despair when faced with their own harmful event, compared to mice who do not observe their fellow mice being harmed. The negative emotional contagion experienced by the bystander mice appears to build resilience against a depressive-like state, according to new research by Sarah Mondoloni and colleagues. Mondoloni et al. demonstrate that resilience in these mice requires an increase in serotonin release in a part of the brain called the lateral habenula. "These findings support the notion that, as is the case in humans, graded trauma can be resilience-promoting, enabling individuals to cope with future challenges," the researchers write. They also note that their findings may refine the current model of the key neuronal circuits involved in depression. The negative emotional contagion in bystander mice was produced when they watched their cagemates receive a mild foot shock, prior to their own shock experience. The researchers suggest that serotonin release helps produce bystander resilience by reducing neuronal bursting in the lateral habenula. This type of neuronal hyperactivity underlies depressive behaviors in the mice. In a related Perspective, Martin Metzger and Jose Donato Jr. say the findings "have great potential relevance to be incorporated into the treatment of major depression, post-traumatic stress disorder and addiction."