Pontine control of ejaculation and female orgasm

Introduction: The physiological component of ejaculation shows parallels with that of micturition, as both are essentially voiding activities. Both depend on supraspinal influences to orchestrate the characteristic pattern of activity in the pelvic organs. Unlike micturition, little is known about the supraspinal pathways involved in ejaculation and female orgasm.

Aim: To identify brainstem regions activated during ejaculation and female orgasm and to compare them with those activated during micturition.

Methods: Ejaculation in men and orgasm in women were induced by manual stimulation of the penis or clitoris by the participants' partners. Positron emission tomography (PET) with correction for head movements was used to capture the pattern of brain activation at the time of sexual climax.

Main outcome measures: PET scans showing areas of activation during sexual climax.

Results: Ejaculation in men and orgasm in women resulted in activation in a localized region within the dorsolateral pontine tegmentum on the left side and in another region in the ventrolateral pontine tegmentum on the right side. The dorsolateral pontine area was also active in women who attempted but failed to have an orgasm and in women who imitated orgasm. The ventrolateral pontine area was only activated during ejaculation and physical orgasm in women.

Conclusion: Activation of a localized region on the left side in the dorsolateral pontine tegmentum, which we termed the pelvic organ-stimulating center, occurs during ejaculation in men and physical orgasm in women. This same region has previously been shown to be activated during micturition, but on the right side. The pelvic organ-stimulating center, via projections to the sacral parasympathetic motoneurons, controls pelvic organs involved in voiding functions. In contrast, the ventrolateral pontine area, which we term the pelvic floor-stimulating center, produces the pelvic floor contractions during ejaculation in men and physical orgasm in women via direct projections to pelvic floor motoneurons.