Diffusion tensor imaging: A new valuable method for understanding male sexual functioning

Abstract

Available information regarding brain pathways involved in male sexual response is mainly derived from animal models and human neuroimaging studies. 1,2 Erection and ejaculation can be considered spinal reflexes supported by the integration of spinal centers of incoming genital sensory signals. However, sexual behavior and sexual pleasure require central integration of several pieces of information, many of which are not derived from the genital area. 2 Evidence from animals shows that sexual excitatory neurochemical mechanisms include mesolimbic and incertohypothalamic dopamine (DA) pathways for sexual incentive motivation, oxytocin, and melanocortin neurons within the hypothalamus and the limbic system to activate sexual attraction, and ascending noradrenaline circuits from hypothalamic, limbic, and cortical regions to increase augment sexual arousal. 2 Data obtained in humans are essentially derived from functional neuroimaging which can detect local neural activity by measuring blood flow, volume, and oxygenation changes while normal adults perform tasks. 2,3 131 PET and functional MRI (fMRI) are the most frequently used techniques. Based on these instruments, it has been reported that brain dimorphic responses to visual sexual stimulation induce the activation of the ventral striatum (including the nucleus accumbens), the amygdala, the anterior cingulate cortex (ACC), and