In a curious study, researchers at the University of California, Los Angeles showed that transcranial magnetic stimulation (TMS) — altering brain activity by zapping specific regions with magnetic pulses — can apparently increase people's libido, at least briefly. Neuroscientist Nicole Prause and her colleagues targeted the left dorsolateral prefrontal cortex (at the left temple), a region involved in reward-seeking. New Scientist explains the curious protocol used by the researchers:
…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's head measured the strength of their brain's 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 – but only after a pause.
Their brainwaves were recorded during this waiting period. "They know they're about to be sexually stimulated, but it hasn't actually happened yet," says Prause. It is the closest analogue for measuring desire in the lab, she adds.
As predicted, after excitatory TMS, participants' alpha waves were weaker – suggesting they were more sexually aroused – than after inhibitory TMS. The team couldn't measure any changes to people's sex lives, as the effects of a single session of TMS are short-lived.
"Zap to the brain alters libido in unique sex study" (New Scientist)