Some people can experience unprovoked, violent outbursts that they are unable to control. But where do these fits of rage come from? A new study may offer clues.
Senior investigator Dayu Lin, PhD, of the Druckenmiller Neuroscience Institute at New York University (NYU) Langone Medical Center, and colleagues found that sudden, violent behavior in male mice was associated with changes in a brain structure called the lateral septum.
Furthermore, they found they could turn aggression on and off in the mice by activating certain brain cells in this region.
The researchers say their findings – published in the journal Current Biology – could help us better understand what triggers aggression in other animals, including humans.
According to the researchers, the lateral septum is connected to the hippocampus – the brain region responsible for emotion and learning – and protrudes into the hypothalamus – the brain region that is closely associated with hormone production and aggression.
The lateral septum also receives signals from both of these brain regions.
For their study, Lin and colleagues surgically inserted a probe into the brains of male mice, using the probe to “excite” certain groups of brain cells by shining a light on them.
The researchers found that by exciting brain cells in the lateral septum, they were able to alter their activity and repeatedly start and stop violent outbursts in the male mice, known as “septal rage,” in which they suddenly attacked other mice.
In detail, the researchers found that by activating cells in the lateral septum, they were able to increase activity in a set of brain cells belonging to a region of the hypothalamus, which the team identified as the ventrolateral part of the ventromedial hypothalamus.
In fact, while the activity in this particular set of brain cells increased with septal stimulation, the activity of another set in the same area decreased.
On analyzing brain cell activity during septal rage in the mice, the team found that the cells that were most active in the ventrolateral area during aggression were those that were most suppressed with septal stimulation, while the cells that were least active during aggression were those that were the most active with septal stimulation.
The team notes that disrupting the connection between the lateral septum and ventromedial hypothalamus did not interfere with the sexual behavior of the mice. Lin says this is an important observation because it suggests that aggression and sexual behavior can be modified independently.
According to Lin, the 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.”
“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.”
The team notes that septal rage has not been identified in humans, but they believe their findings could help pinpoint the brain circuitry involved in other forms of aggression in humans.
Lin and colleagues are now planning to conduct further research in order to identify exactly which brain cells in the lateral septum regulate male aggression and what factors activate or deactivate them to trigger violent behavior.
Last February, Medical News Today reported on a study that found angry outbursts may raise the risk of heart attack.