Brain activation areas of sexual arousal with olfactory stimulation in men: a preliminary study using functional MRI.
There have been extensive studies evaluating the functional neuroanatomy of the brain during visual sexual stimulation. However, little data exist concerning the role of olfactory stimulation in human sexuality. This preliminary study intended to elucidate the brain areas responding to an olfactory sexual stimulus using functional magnetic resonance imaging (fMRI). Eight healthy right-handed heterosexual male volunteers (20-35 years of age), having normal olfaction and no brain diseases, were recruited. During fMRI, a women's perfume was given as an olfactory sexual stimulant in an alternating block design with a 30-second stimulation period followed by a 30-second rest. After the fMRI sessions, the participants provided ratings for both the odorant's intensity and perceived arousal. The study subjects rated the odorant stimulation and perceived sexual arousal response by Likert-type rating scales. Brain activation maps were made by blood oxygenation level-dependent (BOLD)-based fMRI with an echo-planar imaging pulse sequence. Two out of eight subjects experienced "strong" sexual arousal, and three subjects experienced "moderate" arousal during olfactory stimulation, resulting in a mean score of 2.25 on a 4-point scale. The common brain areas activated in response to the odor stimulus in all eight subjects included the insula, the inferior and middle frontal gyrus, and the hypothalamus. The median cingulate gyrus, thalamus, angular gyrus, lingual gyrus, and cerebellar cortex were activated in subjects who had moderate or strong sexual arousal response. Olfactory stimulation with women's perfume produces the activation of specific brain areas in men. The brain areas activated differed according to the degree of perceived sexual arousal response. Further studies are needed to elucidate brain activation response according to the different kinds and intensities of olfactory stimulation.