Name:______Block:______
Tacked up beside Yvon Delville’s computer is a microphotograph of a stressed brain. Swollen clusters of black dots on the rumpled photocopy tell viewers all they need to know about nature versus nurture: your environment, literally, can change your mind.Dr. Yvon Delville's research with hamsters is providing answers to the source of aggressive behavior in humans.
For the past decade Delville, a University of Texas at Austin psychology professor, has conducted research that yields intriguing insights into aggression, social stress and brain biochemistry during a child’s development. Delville’s research has evolved right alongside a spate of media-hyped acts of violence by teenagers over the past few years.
Very curious about the brain mechanisms that control aggression and that may change because of exposure to threat and stress, Delville began to examine the effects of social stress and aggression on a rather late developmental period: adolescence.
Because of their solitary and territorial predisposition, Delville selected golden hamsters as the animal model with which he would experiment. Hamsters are weaned at around 25 days of age, at which time the mother bumps them from the nest, and they venture out to live on their own. At this age they can be described as hamster teens.
In a series of experiments, weaned, male pubescent golden hamsters were placed for an hour a day, for two weeks, into an adult hamster’s cage. The older hamsters’ territorial and antisocial tendencies compelled them to respond with aggression and hostility to the adolescent males, nipping and chasing them. Although the adult hamsters’ behavior was antagonistic and disturbing to the young hamsters, it was not violent or lethal.
A second control group of adolescent male hamsters were simply placed in an empty, unfamiliar cage for one hour a day. Both environments elicited stress reactions in the young hamsters, but the long-term effects of the two different kinds of stress were surprisingly dissimilar.
Cortisol, a stress hormone secreted by the adrenal glands in hamsters and humans, was found to be high in both groups of adolescents during the first day of the experiment. However, the cortisol levels remained elevated for the entire two weeks only in the chased and threatened hamsters. The bullying was a stressor to which they could not seem to adapt.
“The concern with humans is that children who are bathing their brains in cortisol may be at risk for abnormal brain development and irreversible changes to the brain,” said Dr. George Holden, associate chair of The University of Texas at Austin Department of Psychology.
Before they are repeatedly exposed to threat and stress, adolescent hamsters engage in benign play behavior.
Closely observing the young males that had been threatened by hostile adults during the experiment, Delville and graduate students Joel Wommack and Kereshmeh Taravosh-Lahn saw that the traumatized adolescents exhibited exaggerated attack behavior toward smaller males, while being fearful and subordinate with hamsters of equal size or larger. The kitten-like play behavior of their youth had disappeared.
The bullied hamsters had turned into classic bullies themselves. Both their behavior and their brain chemistry revealed a distinct transformation.
“What was found was that the stressors in the environment accelerate the onset of adult-like behavior and the termination of childhood play-fighting,” Delville said. “The exposure to stress and threat make the adolescents attack earlier and act more like adults.”
In contrast, control littermates who had spent time alone in a novel environment showed no lasting changes in behavior.
An examination of the bullied adolescent hamsters’ brains showed significant changes in the concentrations of the neurotransmitters vasopressin and serotonin. In humans, high levels of vasopressin are associated with increased aggression, while serotonin is known to inhibit aggression in males.
The levels of vasopressin in the hypothalamus were lower in abused hamsters than in their littermates in the control set, and levels of serotonin were higher. These neurotransmitter levels correlated well with the cowardly behavior that the stressed hamsters showed and suggested that the chemical makeup of a bully may be unique.
In addition to vasopressin and serotonin, another neurotransmitter called dopamine had also been altered. Visible on microphotographs of neurons was graphic evidence that the expression of dopamine increased when the hamsters were bullied, and this increase occurred in the amygdala, a social integration center in the brain that is responsible for aggression and social interaction.
Most important, the chemical cocktail of the distressed hamsters’ brains seemed to point to the fact that adolescence is a singularly significant period in the development of adult social behavior. Traumatic experiences and the threat of stress and attack early in life affect the topography of the brain as well as behavior.
“Scientists first thought that most brain development occurred in the first four years of life, but Dr. Delville’s research shows that this later time is a highly sensitive and crucial period of development,” said Holden. “Not many scholars are doing studies of bullying, and Delville is one of the only ones who’s successfully linking the behavior with neurochemistry.”
Saliva holds clue to chronic bullying
May 15, 2007
Saliva holds clue to chronic bullying
University Park, Pa. -- Hormones in children's saliva may be a biological indicator of the trauma kids undergo when they are chronically bullied by peers, according to researchers who say biological markers can aid in the early recognition and intervention of long-term psychological effects on youth.
"Bullying is mainly self-reported either by students or observed by teachers," said JoLynn V. Carney, associate professor of counselor education at Penn State.
Carney and Richard Hazler, professor of counselor education at Penn State, looked at the hormone cortisol in students' saliva to evaluate its validity as a reliable biomarker in assessing effects of precursors to bullying. They worked with Douglas Granger, professor of biobehavioral health and human development and family studies; Leah Hibel, doctoral student in biobehavioral health; and Insoo Oh, doctoral student in counselor education.
In humans, this hormone is responsible for regulating various behavioral traits, such as the fight-flight response and immune activity that are connected to sensory acuity and aspects of learning and memory.
"A lot of kids suffer in silence. When you hear of school shootings, or students who commit suicide as reaction to chronic peer abuse, those are kids who are not coping with the abuse by seeking appropriate support," said Carney. "They keep their anger and frustration within and fantasize either how they are going to escape the abuse through suicide or how they are going to get revenge on their abusers."
When a person senses a threat, the cortisol level spikes and learning and memory functions are negatively impacted, Carney said. The body basically focuses the bulk of its attention on surviving the threat. The longer such a spike continues, the more damage it can do to various aspects of a person's physical, social and emotional health. However, when a person undergoes a lengthy period of stress similar to the chronic bullying experience, researchers have found less than normal cortisol reactions that are related to a decreased sensitivity to stress, a sort of numbing or desensitizing effect.
This hypocortisol finding, Hazler noted, has serious physical and psychological implications for kids -- both victim and bystander. Research with adults exposed to repeated stressful events has linked hypocortisol with conditions such as chronic fatigue syndrome, chronic pelvic pain and post traumatic stress disorder (PTSD).
The Penn State researchers tested the saliva of 94 sixth-grade students between ages 9-14, along with a questionnaire on their experience on being bullied or watching someone being bullied, and additional measures of anxiety and trauma.
Since cortisol has a predictable daily pattern of highest levels in early morning and declining levels throughout the day, researchers collected samples of saliva when the students first arrived at school and then again before lunch.
"Lunchtime is one of those less supervised periods when kids are more likely to be bullied. One of the things we are trying to measure is not the reaction immediately following a bullying event, but instead the anticipatory anxiety that takes place with the approach of situations where bullying is more commonly occurs. Even kids who are not bullied suffer from such anticipatory stress because they anticipate watching their friends getting bullied and worry that they might be next," said Hazler.
"It is this anxiety that we believe is most dangerous because that anxiety stays with you. It is not dependent on the bullying happening on a continual basis," he added.
Results from the study suggest that while bullying is directly linked to trauma and anxiety, it is indirectly linked to cortisol levels.
"This confirms our theory that while exposure to a one-time or very rare bullying episode might cause higher cortisol levels, exposure to bullying on a chronic basis would be associated with hypocortisol levels," said Carney and Hazler, who recently presented their findings at the American Counseling Association Convention in Detroit.
The Penn State researchers liken their research on bullying to the study of depression, which used to be solely about psychiatric observations and behavioral tests until researchers began to find biological changes.
"All of a sudden depression was not simply a psychological phenomenon, but it also has a physical aspect with potential medication treatments to support counseling," they noted.