Characterizing sexual arousal physiology using NIRS: a non-invasive approach in translational research

Near-infrared spectroscopy (NIRS) is a noninvasive method for assessing hemodynamic responses related to sexual arousal and dysfunction. This presentation summarizes key findings from three studies using NIRS in both male and female models. In men, penile hemodynamics during visual sexual stimulation varied by probe location, with distinct hemoglobin changes on the dorsal versus lateral sides. Simultaneous brain-genital measurements revealed a ~4-second delay between prefrontal and penile responses, indicating central-to-peripheral arousal dynamics. In female rats, a custom NIRS probe monitored vaginal responses following apomorphine injection. Over eight weeks post-ovariectomy, hemoglobin responses declined alongside reduced estradiol, vaginal secretions, and temperature—hallmarks of female sexual arousal disorder. These studies demonstrate that NIRS can sensitively track genital and cerebral hemodynamics in real-time. Its portability and ease of use support its value as a research and diagnostic tool in sexual medicine.