How 'Silent' Nerve Cells Trigger Aggression in Mother Mice

Recent research from Stockholm University and Karolinska Institutet sheds light on the neural mechanisms behind maternal aggression in mice. This study reveals that certain neurons in the brain, which are typically inactive in non-pregnant females, become highly active during motherhood, leading to aggressive behavior toward intruders. These neurons belong to a pathway that also regulates aggression in male mice, but in females, they remain dormant until pregnancy activates them through hormonal signals such as oxytocin and prolactin.

The researchers found that when these neurons are silenced, mother mice lose their aggressive tendencies, indicating the critical role they play in maternal defense. The activation of this neural circuit appears to be driven by hormonal changes associated with motherhood, enabling behaviors that are outside the normal repertoire of non-pregnant females.

While the study was conducted on laboratory mice, the findings raise intriguing questions about brain plasticity and how behaviors can be switched on or off based on physiological states. The scientists suggest that this mechanism exemplifies a broader principle of neural adaptability, potentially relevant for understanding human behaviors that emerge during specific life phases. According to Stefanos Stagkourakis, the study’s lead author, the same brain network controlling aggression in males is dormant in females until hormonal shifts during motherhood activate it. Neurochemistry expert Christian Broberger emphasizes caution in translating these results directly to humans but considers the findings valuable in exploring how the brain’s flexibility allows behavior changes during certain life stages.

This discovery highlights the intricate relationship between hormones, neural circuits, and behavior, offering new perspectives on the brain’s capacity for adaptation during critical periods like motherhood.