Prefrontal cortex activation and functional connectivity during human male orgasm measured with fNIRS

Background: Understanding of brain activity during orgasm has been limited to hospital-based neuroimaging modalities; this study leverages functional near-infrared spectroscopy (fNIRS) technology to directly observe prefrontal cortex (PFC) responses and functional connectivity (FC) in an ecologically valid setting.Aim: Our aim was to perform the first fNIRS single-subject pilot study to investigate the ability of fNIRS to detect PFC activation during human male orgasm.Methods: The participant viewed a pornographic clip and commenced genital self-stimulation ad libitum. Hemodynamic changes were measured fNIRS bilaterally over the prefrontal cortex before the beginning of visual stimulation and after orgasm. Dynamic FC, heart rate, and relative changes in oxyhemoglobin (HbO) were computed over the whole duration of the experiment.Outcome: Dynamic FC, relative changes in HbO, and pulse rate were all derived from fNIRS recordings.Results: Visual stimulation increased HbO over the left prefrontal cortex and pulse rate with no changes in dynamic FC. Manual self-stimulation also increased pulse rate and decreased mean FC without any changes in HbO. Orgasm increased pulse rate, HbO, and decreased FC bilaterally.Clinical Implications: This study offers insights into prefrontal cortex activation and FC during male orgasm.Strengths & Limitations: The main strength of this study is its novelty, while its main limitation is that it is a pilot study from a single subject.Conclusion: Bilateral activations and decreased dynamic FC accompany male orgasm.