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The main questions addressed in my dissertation are: 1) how does fMRI- measured activity of the brain respond to physical versus imagined stimulation of the genitals, and 2) as the brain activity progresses from response to genital stimulation through orgasm to its resolution, how does the regional activity change? These questions are addressed in the form of two studies: 1) Activation of sensory and other brain regions in response to imagined versus physical genital stimulation, and 2) Brain regional activation upon transition to self- and partner-induced orgasm in women. The first study developed from a genital sensory mapping study (Komisaruk, Wise et al, 2011) in which our control condition revealed the intriguing serendipitous finding that just imagining genital or nipple stimulation activated the same regions of the genital sensory cortex as did actual tactile stimulation of these body regions. We extended this surprising finding by focusing on a comparison between tactile versus imagined stimulation of the nipple and clitoris. We designed two additional conditions -- imagined dildo stimulation versus imagined speculum stimulation -- to investigate possible differences in erotic versus non-erotic imagery. The present findings provide evidence that imagery activates brain regions implicated in bodily sensation, orgasm, and reward, some of which overlap with, and others that are different from, the brain regions that respond to tactile self-stimulation, e.g., paracentral lobule (the “genital sensory cortex”) and the prefrontal cortex, respectively. The second study addressed a major discrepancy in the literature regarding whether frontal and temporal cortical regions are activated (Komisaruk et al., 2004; 2005) or deactivated (Georgiadis et al., 2006; 2009) during orgasm. In addition to the different methods used (fMRI versus PET, respectively), a major procedural difference was that genital self-stimulation was employed in our fMRI studies while genital partner-applied stimulation was used in the PET studies. In an attempt to resolve the discrepancy, in the present study, we compared the regional brain activity observed during self- versus the partner- induced orgasm conditions. We found no deactivation of frontal or temporal regions during self- or partner stimulation-induced orgasm. Neither were there significant regional differences in activity between the self- and partner stimulation-induced orgasms. Consequently, we combined the data from the self-stimulation and partner-stimulation-induced orgasm groups. This analysis revealed widespread activation throughout the brain, including primary sensory, motor, sensory-motor integration and reward regions, whose distribution pattern changed in sequence, leading up to, during, and after orgasm. [Please refer to Appendix H for defense presentation summary of both studies]