Could a brain stimulation device change our sex drive? The first study of this approach suggests that people鈥檚 libido can be turned up or down, depending on the device鈥檚 setting.
The study didn鈥檛 measure how much sex people had in real life, instead it measured participant鈥檚 sexual responsiveness. Unusually, this was done by fixing customised vibrators to people鈥檚 genitals and gauging how their brainwaves changed when they expected a stimulating buzz.
鈥淵ou want to see if they want what you鈥檙e offering,鈥� says at the University of California, Los Angeles. 鈥淭his is a good model for sexual desire.鈥�
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The technique involves transcranial magnetic stimulation (TMS), where a paddle held above the head uses a strong magnetic field to alter brain activity. It can be used to treat depression and migraines, and is being investigated for other uses, including preventing bed-wetting, and helping those with dyslexia.
Reward circuit
The part of the head targeted in this study 鈥� called the left dorsolateral prefrontal cortex, roughly above the left temple 鈥� is involved in the brain鈥檚 reward circuitry.
Prause鈥檚 team wondered if stimulating this area might affect how people feel about sex. One problem is that standard methods of assessing desire are too subjective, says Prause. 鈥淭he only way is to ask someone, 鈥楬ow much do you want to have sex right now?鈥� People might not be willing or able to tell you, or be using the scales differently.鈥�
To get around this, a vibrator was either connected to a sheath that the penis goes in or a small hood that fits over the clitoris. Electrodes on each participant鈥檚 head measured the strength of their brain鈥檚 alpha waves, which are weaker when people are more sexually aroused.
During the experiment, 20 people were given TMS for about two minutes, designed to either excite or inhibit the dorsolateral prefrontal cortex. Next, each volunteer was taken to a room where the EEG electrodes were placed on their head. They were then left to attach the vibrator themselves.
Finally, each participant carried out a task that involved pressing a button as fast as possible when shapes appeared on a screen. Depending on how quick they were, they were given a genital buzz lasting between half a second and five seconds 鈥� but only after a pause.
Desire in the lab
Their brainwaves were recorded during this waiting period. 鈥淭hey know they鈥檙e about to be sexually stimulated, but it hasn鈥檛 actually happened yet,鈥� says Prause. It is the closest analogue for measuring desire in the lab, she adds.
As predicted, after excitatory TMS, participants鈥� alpha waves were weaker 鈥� suggesting they were more sexually aroused 鈥� than after inhibitory TMS. The team couldn鈥檛 measure any changes to people鈥檚 sex lives, as the effects of a single session of TMS are short-lived. To treat depression, for instance, people get several sessions a week, and it is supposed to induce gradual changes to the brain over several weeks.
But people鈥檚 overall sexual responsiveness in the study, as gauged by their brainwaves, did correlate with the number of orgasms they had over the next three days, either through sex or masturbation. Prause says it would be interesting to know if people having TMS for depression report any changes in their sex lives. 鈥淏ut no one asks them.鈥�
at the London School of Hygiene & Tropical Medicine points out that sex is an extremely complicated social phenomenon.聽鈥淭o think you can fix a problem by fixing the physiological components is overly simplistic,鈥� she says. 鈥淏ut if it works there would be a huge market for it.鈥�
PLoS One
