Rats may hold key to human aggression

WBy James Gibby
The Lariat
Baylor University

wACO, Texas (U-WIRE) – Sometimes the human brain can work too well and the results can be less than desirable. Dr. Brad Keele in the psychology department at Baylor University is investigating the causes of anxiety and aggressive behavior. “We are developing a clinically relevant model of impulsive aggression, so we can promote safer, more effective therapeutic treatments,” Keele said.

The amygdala is the structure in the brain Keele researches. The amygdala is part of the limbic system, which is responsible for emotional responses. Specifically, the amygdala controls the fear response. When it works “too well,” the fear response is minimized, resulting in inappropriate aggression.

Keele observes his subjects’ (rats) aggressive behavior by placing an unfamiliar male in the cage with the aggressive male. Under observation, abnormally aggressive behavior is mainly characterized by unprovoked biting.

Scientists control the subject’s aggression in two ways – by chemically decreasing the levels of seratonin in the brain and isolating the subject.

Seratonin is the chemical that helps to maintain “happy” feelings as well as aid with sleep and mood moderation. Rats, like humans, are social creatures becoming agitated when isolated. The aggressive rats are then observed in two trials that normally induce anxiety, the “open field” test and the “elevated plus.”

In the open field test, the subject is placed in a large chamber and observed. Normal behavior for a rat in this case would be to spend most of the time “hidden” against the side of the box, but the aggressive subjects tend to stay in the middle of the box.

The “elevated plus” is a platform in the shape of an addition symbol held approximately a foot off the ground. Two of the arms are exposed and two are walled in.

The subject is set at the intersection and then observed. Rats, being curious by nature, will explore the entire platform, but the aggressive subject will not seek shelter as fast or at all like a control subject. “Why are psychopaths the way they are?” Keele asked. “Probably from a lack of anxiety. Any time we are in a social situation there are outside cues that dictate our behavior. For instance, one would behave differently when sitting with parents than we would out with friends. The amygdala is one of the components of the brain that interprets those cues.”

After these initial trials, the subject’s brain is extracted and cross sections are examined using a methodology that allows the observation of single cells in the amygdala. Drugs are introduced into the cross sections, and the reactions help identify what neurochemicals are influencing the aggressive behavior.

Keele is not trying to explain why your roommate harasses the Wendy’s drive-through guy. He’s identifying the causes of certain behaviors that are anti-social. More specifically, he is trying to find the neurotransmitters and receptors associated with aggression.

“(Humans) have a system that allows us to be social,” Keele said. “When that goes wrong we get things like autism, social misfits or sociopath behavior.”