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Brain’s response to sexual images relates to number of sexual partners

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A person’s interest in sex at a particular moment in time depends on a number of factors such as an attractive face, a pleasant fragrance, or a sexy image. A new UCLA study evaluated the relationship between brain responses to real-world sexual behaviors. The study provided insight into why some individuals are prone to participate in risky sexual behaviors. The study was published in the current online edition of the journal Social Cognitive and Affective Neuroscience.

A key factor for engaging in sexual activity is motivation; however, individuals differ in their response to sex cues; some react strongly and some do not. A higher responsiveness to sexual cues might provide greater motivation for an individual to act sexually; furthermore, risky sexual behaviors typically occur when he or she is motivated by particularly potent, sexual reward cues. Researchers at the UCLA Semel Institute for Neuroscience and Human Behavior have discovered for the first time that how strongly the brain responded to viewing sexual images was related to the number of sex partners a person had in the previous year.

The study authors note that gaining understanding how the brain responds to sexual images could help scientists create a brain stimulation intervention to reduce sensitivity to sexual reward; thus, it might reduce some individuals urge to engage in risky sexual activities. Dr. Nicole Prause, a research scientist in the department of psychiatry in the UCLA Semel Institute for Neuroscience and Human Behavior, and her colleagues used an electroencephalogram (EEG) to measure a particular type of electrical activity in the brains of people as they were viewing a variety of images; some of the images were romantic, others were pornographic, and others had nothing at all to do with sex.

“These are the first data we know of that link brain responses to actual sexual risk behaviors,” explained Dr. Prause. She added, “If your brain responds very strongly even to very tame pictures of sex, then you seem to be easily sexually excited in the real world, too. If we show very explicit sex pictures, eventually everyone’s brain responds strongly. It is those weaker images, just hinting at sex, that show the difference.”

The study group comprised 40 men and 22 women, aged 18 to 40; they completed a questionnaire, which included the question, “How many partners have you had sexual intercourse with in the last 12 months?” They were then shown 225 images that included non-sexual, pleasant images (for example, skydiving), neutral images (such as portraits), and sexual images ranging from G-rated to explicit scenes. While viewing the images, the subjects’ brain activity was measured by an EEG. Specifically, the researchers assessed a type of activity called late positive potential, which reacts to images depending on their emotional intensity.

The investigators found that participants who reported having had a higher number of sexual partners in the previous year exhibited similar late positive potential responses to both the graphic and less-graphic sexual images. The subjects who reported having had fewer intercourse partners in the previous year had different responses. They showed reduced late positive potential responses to the less explicit sexual images and greater response to the more graphic images.

Dr. Prause explained, “This pattern helps tell us why people may choose to pursue new sex partners. For example, some researchers have suggested that people may pursue new partners to experience sexual excitement that they did not experience in their regular lives or with their regular partner. She noted, these results, “suggest that new partners actually might be pursued because people have high sexual excitement in response to any potential partner, whether regular or new. This distinction is very important if we want to help people feel in control of their sexual urges.”