It seems nothing excites the brain more than erotic images, as a new study has found that sensual pictures evoked the strongest response from the brain as compared to any other image.
Researchers at Washington University School of Medicine in St. Louis measured brainwave activity of 264 women as they viewed a series of 55 colour slides that contained various scenes from water skiers to snarling dogs to partially clad couples in sensual poses.
When study volunteers viewed erotic pictures, their brains produced electrical responses that were stronger than those elicited by other material that was viewed, no matter how pleasant or disturbing the other material may have been. This difference in brainwave response emerged very quickly, suggesting that different neural circuits may be involved in the processing of erotic images.
“That surprised us,” says first author Andrey P. Anokhin, Ph.D., research assistant professor of psychiatry. “We believed both pleasant and disturbing images would evoke a rapid response, but erotic scenes always elicited the strongest response.”
As subjects looked at the slides, electrodes on their scalps meas ured changes in the brain’s electrical activity called event-related potentials (ERPs). The researchers learnt that regardless of a picture’s content, the brain acts very quickly to classify the visual image. The ERPs begin firing in the brain’s cortex long before a person is conscious of whether they are seeing a picture that is pleasant or neutral.
But when the picture is erotic, ERPs begin firing within 160 milliseconds, about 20 percent faster than with any of the other pictures. Soon after, the ERPs begin to diverge, with processing taking place in different brain structures for erotic pictures than those that process the other images. “When we present a stimulus to a subject — for example, when a picture appears on a screen — it changes ongoing brain activity in certain ways, and we can detect those changes,” Anokhin says.
Women equally responsive “Usually men subjectively rate erotic material much higher than women,” he says. “So based on those data we would expect lower responses in women, but that was not the case. Women have responses as strong as those seen in men.”
Because the electroencephalogram technology cannot specify brain structures involved in this visual processing. Anokhin says it’s not clear which circuits are reacting to these visual scenes. Recent studies in primates recorded the electrical activity of single neural cells within the brain and have shown that the frontal cortex contains neurons that can discriminate between different categories of visual objects such as dogs versus cats. Whether or not the human prefrontal cortex contains special neurons that are “tuned” for sex remains a subject for future studies.