A new study by researchers at the New York University School of Medicine pinpointed the changes in a specific brain structure tied to controlling anxiety and fear and related to violent, unprovoked outbursts in male mice. The findings reveal that the damage and loss of function in their lateral septum triggered a series of activities in other brain regions that resulted in "septal rage," referring to sudden, violent attacks that typically manifest as attacks on other mice. These results mirror other research that found similar connections in other rodents and some birds.
"Our latest findings show how the lateral septum in mice plays a gatekeeping role, simultaneously 'pushing down the brake' and 'lifting the foot off the accelerator' of violent behavior," Dayu Lin, senior investigator of the study, said in a press release.
The lateral septum is physically connected to the hippocampus, the part of the brain the controls emotion and learning, and both sends and receives electrical signals to it. Furthermore, it also projects into the hypothalamus, the region of the brain tied to aggression and hormone production. Lin claims that although septal rage has not been observed in humans, the study of male aggression in mice could help to uncover the neural circuitry involved in controlling violent behavior in humans.
One of the key findings of the study was the ability to excite specific groups of brain cells using a surgically inserted probe, allowing them to alter lateral septum activity and effectively start, stop or restart aggressive outbursts in male mice. Furthermore, excited lateral septum cells increased the activity of ventromedial hypothalamus cells, while at the same time decreasing nerve cell activity in another region.
Lin believes this points to the lateral septum as the gatekeeper of aggression by activating rage-inhibiting cells and suppressing rage-exciting cells.
"Our research provides what we believe is the first evidence that the lateral septum directly 'turns the volume up or down' in aggression in male mice, and it establishes the first ties between this region and the other key brain regions involved in violent behavior," he said.
The findings were published in the Feb. 11 issue of Current Biology.
