Pheromones and Gender Identity: A pilot study using cerebral electrical activity Molo Mt, Cappai E, Castelli L, Perozzo P, Tomassoni C, Vighetti S CE.R.NE., Fondazione Carlo Molo, Torino, Italy

AIM OF THIS STUDY To examine cerebral electrical activity during the nasal administration of male and female pheromones in transsexuals and eterosexuals, during erotic visual stimulation

The vomeronasal organ (VNO) Here is the VNO pit

The vomeronasal organ: connection with the hypothalamus

Subjects: 6 heterosexual male 6 heterosexual female 6 male-to-female (MtF) transsexuals First session MtF Estratetraenol/Androstadienone Males Estratetraenol/placebo Females Androstadienone/placebo Second session MtF the opposite Males the opposite Females the opposite

Results A specific software transformed all the numerical values recorded by each electrode into a spectrum of colours, thus creating a brain map

Procedure MtF Estratetraenol Males Estratetraenol/placebo Females Androstadienone/placebo MtF Androstadienone Males the opposite Females the opposite Results 1) In the MtF subgroup comparing the Androstadienone to the Estratetraenol condition we found: major decrease in alpha rhythm (p=0.015) major increase in beta rhythm (p=0.001) with androstadienone = cerebral arousal

Androstadienone VS Estratetraenol MTF Androstadienone VS Estratetraenol Example of a brain map referring to the frequency of β waves. The two coloured maps show the mean values of β frequency activation. As indicated in the column, the colour spectrum goes up from a lower value to a highier one, where the blu area represents a stronger activation. The gray map shows the statistical difference between the two conditions. Data statistically significant with p<0.05 are in the red zone, left frontal region

Procedure MtF Estratetraenol Males Estratetraenol/placebo Females Androstadienone/placebo MtF Androstadienone Males the opposite Females the opposite Results 2) During the Androstadienone condition, comparing the MtF and the Female subgroups we found: major decrease in alpha rhythm (p=0.045) major increase in beta rhythm (p=0.045) in the MtF subgroup = cerebral arousal

MtF VS Heterosexual females Androstadienone MtF VS Heterosexual females A picture similar to the previous, but the major activation of MtF compared to women is bilaterally in frontal region.

Procedure MtF Estratetraenol Males Estratetraenol/placebo Females Androstadienone/placebo MtF Androstadienone Males the opposite Females the opposite Results 3) No significant differences were found among the other conditions:  between the MtF and the heterosexual males in the estratetraenol condition  between the estratetraenol condition and placebo in the heterosexual males between the androstadienone condition and placebo in the heterosexual females

Conclusion Our study highlights two important findings: New evidence of biological differences between transsexuals and men Transsexuals are more aroused than heterosexuals by erotic stimuli