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This Is Your Brain on Violence

Research using brain-scanning technology finds that images of violence stimulate specific responses in the human brain that do not occur in reaction to other types of imagery.
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Violent imagery "has privileged access to the brain," according to a Columbia University study that provides provocative new evidence in the ongoing debate over the effect of media violence.

A team at Columbia's Functional Magnetic Resonance Imaging Research Center found that on-screen violence stimulates specific responses in the human brain — activity that does not occur in reaction to other types of imagery. The study suggests that repeated exposure to violent images heightens our readiness to take action even as it suppresses the region of the brain that modulates aggression.

While these findings reveal violence has a unique effect on the brain, understanding the relationship — if any — between exposure to violent media and violent behavior remains an elusive goal, cautioned Joy Hirsch, director of the center and senior author of the paper.

"But we're chipping away at it," she said. "This is fertile grounds for further study."

The purported effects of media violence have been studied and analyzed for at least 50 years. According to a history of the topic compiled by the Canadian Media Awareness Network, researchers in 1956 asked 12 children to watch a violent cartoon while another dozen viewed a non-violent cartoon. As the kids played together afterward, those who had watched the violent cartoon were considerably more likely to hit other children and break toys.

In the decades since, researchers have disagreed sharply on the effect of media violence, some seeing a clear link while others remain skeptical. The Columbia team is one of the first to explore the issue through the use of brain-scanning technology.

When the study was initially proposed by an undergraduate, Christopher Kelly (now a Columbia medical student, and the paper's first author), Hirsch's first reaction was, "Surely this has been done before." But she found it had not — in part because the technology that makes it possible is relatively new.

"We've had 15 years of good, functional MRIs, but there has been a quantum leap in their capabilities in the past four or five years," she said. "We have much more understanding of the emotional system (in the brain), and techniques to study it are better."

Using mainstream Hollywood movies, Hirsch's team collected clips and into three categories. One group depicted acts of violence. A second featured images of fear — including facial expressions of terror - but no actual violence. A third was composed of intense physical activity that did not involve the threat of violence, such as dance or sporting events.

As the participants — all Columbia undergraduates or graduate students who volunteered to participate — watched the images, the researchers scanned their brains and recorded the activity. To understand what they saw, it is important to remember that the brain is an incredibly complex organ in which certain parts work together to process information and come up with an appropriate response.

"Many recent studies show tugs-of-war, if you will, within the brain," Hirsch said. "One area is pulling on another. We are beginning to see the cascade of neural events that result in behavior. That's enormously exciting."

One such cascade begins at the amygdala, which Hirsch called "a very specialized area of the brain — sort of a front-line emotional responder. It responds to aggression and other emotionally negative events. It's important for survival.

"But we have other parts of the brain that are directly connected to it that have a suppressive effect on it. They send inhibitory signals to the amygdala. One of them is the orbital frontal cortex.

"The amygdala sets off the siren, essentially. The first alarm. These other units of the brain then evaluate the threat and modulate the response."

Given this understanding, the researchers were not surprised to find that violent images set off both the amygdala and the orbital frontal cortex. What interested them was that with repeated exposure to the violent imagery, the inhibitory signal from the orbital frontal cortex to the amygdala — in which it essentially conveys the message "cool off!" — gradually grew weaker.

"This did not happen with the other control stimuli (i.e., the images showing sports action or frightened faces)," Hirsch said. "It is specific to violence.

"The other thing we observed, but didn't expect, is there was also an up-regulation of the motor cortex (in response to violent imagery) — the part of the brain that plans for action," she added. "That means there was preparedness for fight or flight."

Hirsch is quick to add that many parts of the brain are involved in aggression, and that her study does not address the issue of behavior. But she considers this a fertile area for further research. An interesting follow-up study, she said, would look at what is happening in the brain while people are playing violent video games. Being an active participant in virtual violence could provoke different neural responses than passively watching images of bloodshed.

Due to funding limitations, Hirsch has no immediate plans to conduct such a study. "But it's something I'm very interested in," she said.

Given the amount of violence in the media and the amount of time children and adults spend watching it, "I think we have a social obligation to study this," she said. "We've created this situation. Now we have to deal with it."