Aggression generates sensation of reward in brain: mouse study
Aggressive behaviour is very rewarding from a cognitive perspective, with the brain interpreting it as a pleasurable activity on par with sex or recreational drugs, a new mouse study suggests.
"It is well known that dopamine is produced in response to rewarding stimuli such as food, sex and drugs of abuse," Maria Couppis, who conducted the study as her doctoral thesis at Vanderbilt University in Nashville, said in a release. "What we have now found is that it also serves as positive reinforcement for aggression."
Dopamine is a hormone-like substance that acts as neurotransmitter translating the effects of things like drugs into sensations.
The study of mice involved placing a female and male mouse in a cage, with five other mice in a separate enclosure. In the course of the experiment, the female mouse would be removed from the cage and temporarily replaced with an "intruder" mouse. The aggressiveness of the male mouse was then observed.
Over time, the male mouse, trained to poke a target with its nose if it wanted the intruder to arrive again, increasingly signalled it wanted the other mouse to return and that it perceived the encounter as a reward.
When the male and female mice were given drugs that stopped the dopamine receptors in their brains, they stopped being so eager to have the intruder mouse return.
"We learned from these experiments that an individual will intentionally seek out an aggressive encounter solely because they experience a rewarding sensation from it," said Craig Kennedy, professor of special education and pediatrics at Vanderbilt.
"This shows for the first time that aggression, on its own, is motivating, and that the well-known positive reinforcer dopamine plays a critical role."
The study will be published online the week of Jan. 14 in the journal Psychopharmacology.
, opps I mean 
