Thinking about doing something that you shouldn't? Those bad intentions originate from a specific part of the brain, and a new study published in Nature Neuroscience identified just where that is.
The warning signs of premediated violence turn up in the hypothalamus, a part of the brain that also regulates temperature, hunger and sleep. Specifically, the ventrolateral part of the ventromedial hypothalamus, or VMHvl, is the area responsible for our ill will.
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Understanding the neurological underpinning of aggressive actions in the brain could provide scientists with new therapeutic techniques for controlling these behaviors, which has implications for violent crime prevention. However, any treatments to that effect are "only a distant possibility, even if related ethical and legal issues could be resolved," according to researcher Dayu Lin of the Neuroscience Institute at NYU Langone.
Because of those same "ethical and legal issues," the subjects used in the NYU study were not humans but instead mice, which share many of our brain structures. The researchers monitored aggression in male mice trained to attack weaker rodents.
The aggressive mice would have to choose between two options: It could stick its snout an empty port, yielding no reward, or a hole leading to another mouse, which resulted in a food reward.
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In the angry mice, just before they literally were about to stick their noses in another mouse's business, nerve cell activity in the VMHvl spiked. Activity increased 10 times normal levels after the aggressive rodents spotted the weaker ones.
After the researchers genetically inhibited VMHvl activity, the once-aggressive mice calmed down, though retained some of their learned behaviors associated with the training in order to get a food reward.
"Our study pinpoints the brain circuits essential to the aggressive motivations that build up as animals prepare to attack," Lin said in a statement.
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The latest study continues a thread of research probing the neurological roots of aggression. Last month, the same scientists identified what they described as the origin of rage in the male animal brain. Damage to the lateral septum, a part of the brain linked to control of anxiety and fear, triggers a domino effect in the brain that leads to "septal rage," or outbursts of unprovoked violence.
In addition to identifying the structure associated with rage, the researchers proved able to control aggressive outbursts, starting and stopping them using a surgically inserted probe.
Septal rage has not been seen in people, but the study of the neurological patterns underling this condition could provide a window that allows scientists to understand violent behavior in humans.