Erotic images elicit strong response from brain
- From: adam.kamil@xxxxxxxxx
- Date: 16 Jun 2006 19:54:39 -0700
http://www.rxpgnews.com/psychiatry/psychology/coginitivescience/article_4457.shtml
Jun 15, 2006, 11:36, Reviewed by: Dr. Priya Saxena
"We believed both pleasant and disturbing images would evoke a rapid
response, but erotic scenes always elicited the strongest response."
Researchers at Washington University School of Medicine in St. Louis
measured brainwave activity of 264 women as they viewed a series of 55
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," 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 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 says.
Pictures appeared on a screen at 12 to 18 second intervals, and each
picture remained on the screen for about 6 seconds. The subjects were
instructed to do nothing other than look at the pictures.
A great deal of past research has suggested that men are more visual
creatures than women and get more aroused by erotic images than women.
Anokhin says the fact that the women's brains in this study exhibited
such a quick response to erotic pictures suggests that, perhaps for
evolutionary reasons, our brains are programmed to preferentially
respond to erotic material.
"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 (EEG) technology cannot pinpoint
specific brain structures involved in this visual processing, Anokhin
says it's not clear exactly 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.
"The newer and more advanced technologies such as MRI and PET provide
much better spatial resolution," he says. "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."
Most of Anokhin's research is centered on the genetic and
neurobiological bases of behavioral traits that might be associated
with increased vulnerability to alcoholism and addictive disorders. He
believes this study could contribute to that work by detecting
differences between responses to images with different emotional
significance. Because many psychiatric disorders also are associated
with poor processing of signals associated with reward and pleasure, as
well as sexual disturbances, he believes the way the brain processes
emotional pictures, including erotic materials, might help scientists
better understand some forms of mental illness.
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