Nerve cell activity in the hypothalamus peaks just before initiating aggressive behavior, researchers have found, after conducting a study in mice.
There are, of course, ethical implications that need to be considered, but their study - published in Nature Neuroscience - is the first to link warning signs of premeditated violence, such as stalking, bullying and sexual aggression, to a specific part of the brain.
The hypothalamus, which was implicated in the study, is the area of the mammalian brain that controls body temperature, hunger and sleep.
Led by Dayu Lin, PhD, from the Neuroscience Institute at the New York University (NYU) Langone Medical Center, the study was conducted in mice, which share many brain structures with humans.
Lin and colleagues recently published another study that found sudden, violent behavior in male mice was associated with changes in a brain structure called the lateral septum.
For this latest study, the researchers trained male mice to attack weaker ones. The team then observed how aggressively the male mice tried to get access to and harass other mice.
The researchers measured the number of attempts the aggressive mice made to poke their noses through holes leading to another mouse entering their territory so they could then attack them.
Stopping VMHvl activity halts aggressive motivations
Although past studies have linked aggressive behavior to the hypothalamus, the latest study looked specifically at the ventrolateral part of the ventromedial hypothalamus (VMHvl), which is centrally located in the brain underneath the hypothalamus.
The researchers used probes that measured nerve activity in the mouse brains before, during and after they planned to attack.
From this, they observed that nerve cell activity in the VMHvl peaked just before the mice poked their noses through the holes, and this occurred even when the hostile mice could not smell or see the victim mice.
The team also found that nerve cell activity in the VMHvl increased ten-fold during the first moments after the victim mice appeared.
Interestingly, Lin says that genetically stopping VMHvl activity brought a halt to almost all of the aggressive motivations in the mice, but it did not stop other learned behaviors, such as nose poking to get a treat.
Targeting human brain 'a distant possibility'
"Our study pinpoints the brain circuits essential to the aggressive motivations that build up as animals prepare to attack," says Lin.
She notes that clinical implications for their findings are significant. For example, if they can learn how to control aggressive motivation, she says there could be a way to control such behaviors without using sedation.
In the meantime, however, targeting the VMHvl in the human brain in order to stop aggression is "only a distant possibility, even if related ethical and legal issues could be resolved," Lin says. She adds:
"That said, our results argue that the ventrolateral part of the ventromedial hypothalamus should be studied further as part of future efforts seeking to correct behaviors from bullying to sexual predation."
Lin and her team plan to begin investigations into which nerve cells and circuits in the VMHvl play a part in initiating and executing aggression.
Medical News Today recently reported on a study that suggested a hostile attitude in youth is linked to memory problems in later life.