Background and Objective: The goal of this research was to define to mechanism of action for sexual arousal between the mind and the body for young men and women in the San Francisco Bay area.Working within the paradigm of the Sexual Response Cycle,helped to create the framework for understanding the male and female sexual response with sexual function and dysfunction at the core.The young male cohort was a group of heterosexual men who had experienced sexual function previously.The young female cohort was a group of heterosexual women who had experienced hypoactive sexual desire disorder(HSDD)previously.To review the fMRI research with male and female sexual arousal conducted at Stanford Medical Center and to propose some new research hypotheses.Methods: Young(between the ages of 18 and 30),heterosexual,right-handed(for the sake of research consistency)men and women were recruited for this research,after obtaining IRB approval and Informed Consent.The young male study was completed within one month of initiating recruitment.The initial female study took six months and over 280 applicants to find 20 participants for the initial study.This cohort was used to define the stimuli for the women because we thought it might be different than it was for the men.The second female study took over a year to complete and included 20 young women with no history of sexual dysfunction(NHSD)as compared to 16 women with HSDD.Each group included approximately 20 participants initially,after the phone screening,completing the Informed Consent,and remaining in the 3T fMRI scanner at Stanford Medical Center to view and respond to the various stimuli as it was presented to them.The protocol called for them to receive the stimuli in various orders between relaxation,sports stmuli,and sexual stimuli.Their heart rate,respiration,sexual/genital responses were monitored with either a turgometer(male)or vaginal photoplethysomograph(VPP-female),behavioral responses,and brain activation were all correlated with the kind of stimuli they were receiving at the time.Results: After a block analysis data assessment,the results demonstrated the young men had sexual arousal activation: in the right subinsular region,including the claustrum,left caudate and putamen,right middle occipital/middle temporal gyri,bilateral cingulated gyrus and right sensiormotor and pre-motor regions.This was in contrast to the female results,which demonstrated more behavioral response to the erotic stimuli by the NHSD women.Additionally,women with NHSD showed more activation in the bilateral entorhinal cortex.And,women with HSDD showed more activation in the medial frontal gyrus(Broadman Area-BA10),right inferior frontal gyrus(BA 47)and bilateral putamen.Findings were consistent across three experimental sessions.The results suggest differences between NHSD and HSDD women in encoding sexual stimuli,retrieval of past erotic experiences or both.Conclusions: While this presentation demonstrates gender differences of sexual arousal in brain activation,clearly,there is more work to be done to define the science behind the hypotheses.Some additional hypotheses to be explored might include: comparing male and female sexual arousal with fMRI technology across the lifespan;and,with various diseases and disorders.Once the science is defined,we might be able to more effectively understand the etiology and efficacy of various treatment methods for various diseases and disorders.