23 February 1999

Brain Mapping Of Sexual Arousal

The complex cerebral bases of human sexual behavior have rarely been investigated but now Serge Stoleru and colleagues at CERMEP have unveiled one of the biological aspects of this supposedly abstract phenomenon we call desire. They have not only found that the activity of the brain is related to sexual desire, but have also identified the precise brain areas concerned.

Visual stimuli play a major role in human sexuality. The researchers therefore selected eight healthy young men aged between 21 and 25, all of whom were right-handed (emotions are lateralized in the brain, meaning that subjects in this type of study must all be either right-handed or left-handed), and showed them a series of three radically different six-minute films, in the following order: an emotionally neutral sequence (a geographic documentary); an extract from a comedy film (to provoke positive emotions) and a sexually explicit sequence (eliciting sexual emotions). The volunteers watched the films while being monitored by a positron emission tomograph, a device which provides extremely detailed images of the brain and can be used to identify brain regions that are activated during different mental operations.

Five brain areas were found to be more active during the sexually explicit film than during the neutral and/or comic film.

The researchers also measured various physiological parameters, especially the blood concentration of testosterone, the principal male hormone. The testosterone level rose very strongly during the sexually explicit film; it also increased slightly during the comedy sequence. These results may throw light on the neurophysiological basis of sexual arousal dysfunctions, which may take the form of sexual apathy or, on the contrary, pathological hyperactivity leading to deviant behavior such as rape. Serge Stoleru and colleagues have already started to study men with a marked and durable loss of sexual desire.