July 19, 2024

Brain Mechanism in Mice Teaches them to Avoid Bullies: Insights into Human Social Disorders

 The study, published in Nature, reveals that after losing a fight, mice will flee from the aggressor for weeks, influenced by a distinct area of the hypothalamus known as the anterior ventrolateral part of the ventromedial hypothalamus (aVMHvl). This region, responsible for controlling hunger, sleep, and hormone levels, plays a critical role in driving longer-lasting avoidance behaviors after being defeated.

Initially, when rival mice encounter each other, the scent information about opponents is not strong enough to activate the aVMHvl cells and prompt a retreat response. However, once a fight begins and the defeated mouse experiences pain, oxytocin, commonly known as the cuddle hormone, is released. While oxytocin is typically associated with positive behaviors like caregiving, in this case, it binds to oxytocin receptors on aVMHvl cells and signals danger. This links the pain signals to the scent of the aggressor, conditioning the bullied mouse to avoid the aggressor based solely on its smell in future encounters.

The study’s lead author, Takuya Osakada, Ph.D., emphasizes the role of oxytocin in driving learning from traumatic social experiences within the hypothalamus. While the hormone is often associated with positive behaviors, the study highlights its crucial role in social conflict. Osakada, a postdoctoral fellow in the Departments of Psychiatry and Neuroscience and Physiology at NYU Langone Health, also suggests that while mice and humans share similar brain chemistry, further research is needed to understand if these findings can be translated directly to humans.

Previous research has shown that various species, including humans, exhibit retreat behaviors following social defeat. Additionally, studies in children have linked experiences of bullying to increased social isolation and school absences. This new study is the first to explore rapid social learning immediately following a single defeat, shedding light on how animals quickly adapt their behavior in response to traumatic experiences.

The research involved observing hundreds of mice, which were exposed to a rival for ten minutes before being separated. The scientists also measured the animals’ brain activity before and after a conflict. The results showed that 24 hours after a single defeat, social interaction levels dropped to just 20% of pre-defeat levels. Furthermore, the study revealed that pain triggers the immediate activation of oxytocin-releasing brain cells located adjacent to the aVMHvl region.

To further investigate the role of the aVMHvl in social avoidance, the researchers blocked the oxytocin receptors on these cells. They found that mice with blocked receptors were less likely to retreat from their aggressor in subsequent encounters. Conversely, when the aVMHvl cells were artificially activated, even mice that had not lost a fight preferred to keep to themselves.

These findings provide valuable insights into the role of oxytocin and the aVMHvl region in social behavior and learning in mice. Understanding these mechanisms may lead to a better understanding of human social disorders and potentially open avenues for developing therapeutic interventions to improve social interactions in individuals affected by such disorders.

1. Source: Coherent Market Insights, Public sources, Desk research
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