Wednesday, November 30, 2016

Sexual violence may reshape the female brain

“My independence, natural joy, gentleness and steady lifestyle I had been enjoying became distorted beyond recognition. I became closed off, angry, self-deprecating, tired, irritable, empty.” These chilling words, penned in a letter that a woman known only as “Emily Doe” read aloud in June to her attacker, former Stanford University student Brock Turner, offer a mere glimpse into the emotional devastation left by her rape. For Doe and others among the estimated one in three women who experience sexual violence, the damage can ripple throughout a lifetime.

But sexual violence may leave more than just emotional scars:  New research suggests sexual violence may change victim’s brains.

A recent study published in Scientific Reports found that sexual aggression from older male rats not only boosted the production of stress hormones in pubescent females, but it also disrupted their ability to learn various behaviors, including those needed to care for offspring. Females that struggled with maternal behaviors also had poorer survival of newly generated neurons in the hippocampus, a brain region crucial in memory and learning.

Women tend to be more sensitive to stress than men. Study lead author Tracey Shors of Rutgers University has wondered whether stress specifically from sexual violence changes the brain and learning in females. Despite growing openness to talking about sexual violence, “certainly it hasn’t been studied at a scientific level,” she says. “What does that actually do to the female brain?”
To find out, Shors and her colleagues developed the Sexual Conspecific Aggressive Response, or SCAR, a model of how stress from experiencing sexual aggression affects females. (Historically, lab models of stress have focused solely on its effects on males.) SCAR involves pairing a pubescent female rat with an adult male or adult female, or placing her alone in an unfamiliar cage for 30 minutes a day. An adult male caged with a pubescent female typically chases her genital region and pins and mounts her as she tries to escape.

After the experiment, Shors’ team measured levels of the stress hormone corticosterone in pubescent females’ blood. Sure enough, those that had been caged with adult males had higher corticosterone levels than those that hadn’t. The researchers also measured the pubescent females’ learning ability by using electrodes to stimulate their eyelids whenever a sound played, which trained them to eventually blink when they heard the tone, even without the stimulus. Pubescent females that had been paired with adult males did not learn this response as well as females that had not been exposed to them. The researchers also observed whether pubescent females exhibited maternal behaviors — like licking and grooming — when housed with two newborn pups. Those that had been caged with an adult male showed fewer maternal behaviors than the controls. “You have to learn new ways of thinking and behaving if you want your offspring to survive,” Shors says. “It has implications for not only women, but the species.”

What’s more, pubescent females that showed fewer maternal behaviors as a consequence had fewer newly generated cells in the hippocampus, necessary for learning about time. “If you’ve had a lot of trauma in your past, you might have difficulty paying attention to what’s happening in the present,” Shors says, which could explain the learning deficiencies her team observed.To be sure, we can’t completely generalize these findings to humans. J. Douglas Bremner of Emory University wonders whether adult male rats naturally display sexual aggression when trapped with younger females — “just a general question to make sure that the degree to which the model of this type of stress really corresponds to what it would be for humans,” he says. And as with any new model, SCAR “should be replicated by another group.”

Shors agrees SCAR can only go so far in explaining how sexual violence affects women and girls. She cautions against a fatalistic interpretation of the results — that just because a woman experiences sexual violence, she can’t learn maternal or other behaviors. Still, SCAR does highlight potential changes. Ultimately, Shors hopes the model will lead to effective interventions. Currently, Shors is providing MAP Training, an intervention that combines meditation and aerobic exercise, to women who have experienced sexual violence. “If we’re really going to help women with these experiences, we need to learn about how it’s changing their brain and behavior. If we do that, maybe we can design interventions that are more tailored to their needs and lives and experiences.”


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