Aggression is as rewarding as sex, food and drugs

January 15th, 2008 - 1:36 pm ICT by admin  

Washington, Jan 15 (ANI): Brain processes aggression as a reward, just like sex, food and drugs, says a new study.

The study, led by Craig Kennedy, professor of special education and paediatrics at Vanderbilt University, offers insights into humans propensity to fight and their fascination with violent sports like boxing and football.

Aggression occurs among virtually all vertebrates and is necessary to get and keep important resources such as mates, territory and food. We have found that the reward pathway in the brain becomes engaged in response to an aggressive event and that dopamine is involved, Kennedy said.

Dopamine receptors have key roles in many processes, including the control of motivation, learning, and fine motor movement.

Maria Couppis, who conducted the study as her doctoral thesis at Vanderbilt, said: It is well known that dopamine is produced in response to rewarding stimuli such as food, sex and drugs of abuse. What we have now found is that it also serves as positive reinforcement for aggression.

Researchers conducted the study on a pair of mice, one male, one female, which was kept in one cage and five intruder mice were kept in a separate cage.

The female mouse was temporarily removed, and an intruder mouse was introduced in its place, triggering an aggressive response by the home male mouse.

Aggressive behaviour included tail rattle, an aggressive sideways stance, boxing and biting.

The home mouse was then trained to poke a target with its nose to get the intruder to return, at which point it again behaved aggressively toward it. The home mouse consistently poked the trigger, which was presented once a day, indicating it experienced the aggressive encounter with the intruder as a reward.

The same home mice were then treated with a drug that suppressed their dopamine receptors. After this treatment, they decreased the frequency with which they instigated the intruders entry.

We learned from these experiments that an individual will intentionally seek out an aggressive encounter solely because they experience a rewarding sensation from it. 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, Kennedy said.

The study is published in the journal Psychopharmacology. (ANI)

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