Mirror neurons control erection response to porn
New Scientist, 16 June 2008
have to be a scientist to observe that pornographic images lead to
erections in men. But you would have to be one to show those images to
volunteers while meticulously measuring the volume of response in the
brain and penis.
Harold Mouras, at University of Picardie Jules
Verne in Amiens, France, and his colleagues wanted to understand the
cerebral underpinnings of visually-induced erections.
suspected there might be a role for mirror neurons, a special class of
brain cell that fires both when people perform an action and when they
observe it being performed.
The researchers invited eight young
men into the lab and asked them to view three types of video clips.
Along with late-night fishing documentaries and snippets of Mr Bean,
the volunteers got to see erotic videos of men stroking naked women,
enjoying fellatio and engaging in intercourse.
the volunteers watched the movies, the researchers watched their brains
using functional magnetic resonance imaging (fMRI).
kept tabs on the tumescence of the other target organ, using a
hand-crafted "penile plethysmograph" - essentially an airtight tube in
which the enlarging penis causes measurable pressure changes.
As expected, all the subjects got erections and many parts of the brain lit up.
the volume of the erections correlated with the strength of activation
in a part of the brain called the pars opercularis, which is known to
display mirror neuron activity. Even more intriguing, the brain
activation, say the researchers, precedes the penile response.
"The mirror neurons are like the command," says Mouras. "The activation comes before the erection."
study, says Mouras, is the first to suggest that mirror neurons are
involved not only in observed actions, but in the "automatic" responses
to those observations - in this case, erection.
Ramachandran, at the University of California at San Diego, who also
studies mirror neurons, calls it a "bold" study, and congratulates the
group on defying the taboo on studying human sexual physiology.
he thinks it is perfectly plausible that mirror neurons play a role in
how porn turns us on, he says more needs to be done to understand what
that role is. For a start, he says, a large number of the brain's
structures seem to be involved, not just the pars opercularis, and the
interaction between these regions in response to porn is unclear.
"It doesn't give you an experimental lever into the problem," he adds.
while Ramachandran agrees that the timing of mirror neuron activation
and erection is probably critical, fMRI isn't accurate enough to show
clearly what is going on with these brain regions over such short time
Journal reference: NeuroImage (DOI: 10.1016/j.neuroimage.2008.05.051)