Brain activation-based sexual orientation in female-to-male transsexuals.

This study was performed to identify the sexual orientation in association with brain activation pattern in response to visual erotic stimuli in female-to-male (FtM) transsexuals by using functional magnetic resonance imaging (fMRI). Eleven FtM transsexuals who have had sex-reassignment surgery to alter their natal bodies with the gender-identity disorder were participated. Brain activation for sexual orientation was induced by visual stimuli with female and male erotic nude pictures compared with emotionally-neutral pictures. During viewing the erotic female pictures, the brain areas dominantly activated consist of the superior frontal gyrus, supplementary motor area, anterior/median cingulate gyri and hypothalamus, whereas during viewing male pictures, the brain areas with predominant activities were the middle frontal gyrus, precentral gyrus, middle temporal gyrus, fusiform gyrus, angular gyrus, precuneus, superior/middle occipital gyri, cerebellar cortex and vermis. These findings demonstrate that the brain activation patterns induced by viewing male or female erotic pictures show some correlation to the sexual orientation opposite to the genetic sex in FtM transsexuals. This study would be helpful to understand the neural mechanism associated with visual sexual arousal in patients with gender disorder.

A new potential of blood oxygenation level dependent (BOLD) functional MRI for evaluating cerebral centers of penile erection.

It is well known that penile erection is dependent on commands from the central nervous system. However, there has been little research on the central control of penile erection. The aim of this study was to evaluate, for the first time, the cerebral centers of penile erection using BOLD-functional MRI. Functional magnetic resonance imaging (fMRI) on a 1.5T MR scanner was performed in 12 sexually potent male volunteers (mean age: 23) and two hypogonadal impotent patients. In this study, blood oxygenation level dependent (BOLD) technique was utilized to create fMRI reflecting local brain activities. Real-time visual stimulation was performed with an alternatively combined erotic and non-erotic film to identify and quantify the activated brain regions associated with sexual response. Subjective sexual arousal and penile erection responses were assessed using 5-point scales ranging from 1 (no change) to 5 (maximal increase). In normal volunteers, the mean scores on subjective sexual arousal and penile erection by sexual stimulation with erotic film were 3.0 and 3.3 respectively, whereas there were no changes by non-erotic stimulation. During the visual stimulation the occipital cortex was activated by either an erotic or non-erotic film, the erotic film gave 150-200% stronger activation. However, more than seven of the 12 healthy subjects were significantly activated in the areas of inferior frontal lobe, cingulate gyrus, insula gyrus, corpus callosum, thalamus, caudate nucleus, globus pallidus, and inferior temporal lobe by erotic stimulation. In the hypogonadal patients, brain activation in response to the erotic film decreased compared to normal volunteers, however, it was restored by testosterone supplementation. These results are the first demonstration to show the functional neuroanatomy of the brain associated with sexual arousal by visual sexual stimulation using BOLD-based fMRI. Further studies are needed to verify that fMRI provides an important new tool in evaluating the cerebral center of the penile erection.

Blood-oxygenation-level-dependent functional magnetic resonance imaging for evaluating cerebral regions of female sexual arousal response.

OBJECTIVES: To evaluate, for the first time, the cerebral regions associated with female sexual arousal evoked by visual stimulation using noninvasive blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI). METHODS: A total of 6 healthy right-handed female volunteers (mean age 33 years, range 25 to 41) underwent fMRI on a 1.5-T MR scanner, in which the BOLD technique was used to create fMR images reflecting local brain activities. Real-time visual stimulation was performed with alternatively combined erotic and nonerotic films to identify the activated brain regions associated with sexual response. The perceived sexual arousal response was assessed using a scale ranging from 1 (no change) to 5 (maximal increase). RESULTS: The mean score for perceived sexual arousal by erotic visual stimulation was 2.7 on the 5-point scale and was unchanged by nonerotic stimulation. During the visual task, the occipital cortex was activated by both the erotic and the nonerotic films; however, the following cerebral areas were significantly (P <0.05) activated, varying from 4 of 6 to 6 of 6 women: inferior frontal lobe, cingulate gyrus, insula gyrus, corpus callosum, thalamus, caudate nucleus, globus pallidus, and inferior temporal lobe. CONCLUSIONS: This study is the first to evaluate noninvasive BOLD-fMRI in identifying cerebral regions associated with sexual arousal response evoked by visual stimulation in women.