A new study suggests the brain is quickly turned on and “tuned in” when a person views erotic images.
School of Medicine researchers measured brainwave activity of 264 women as they viewed a series of color slides that contained various scenes from water-skiers to snarling dogs to partially clad couples in sensual poses.
What they found may seem like a “no-brainer.” 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,” said 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 measured changes in the brain’s electrical activity called event-related potentials (ERPs). The researchers learned 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, unpleasant or neutral.
But when the picture is erotic, ERPs begin firing within 160 milliseconds, about 20 percent faster than occurred 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 said.
Past research has suggested that men are more visual creatures than women and get more aroused by erotic images than women. Anokhin said the fact that the women’s brains in this study exhibited such a quick response to erotic pictures suggests that, perhaps for evolutionary reasons, human brains are programmed to preferentially respond to erotic material.
Because the electroencephalogram (EEG) technology cannot pinpoint specific brain structures involved in this visual processing, Anokhin said it’s not clear exactly which circuits are reacting to these visual scenes.
“The newer and more advanced technologies such as MRI and PET provide much better spatial resolution,” he said. “Those methods can better localize areas of brain activity, but ERPs have a much better temporal resolution. The EEG can record neuronal activity in real time. When measuring activity in milliseconds, any delay is undesirable.”