Psychophysiologic correlates of nocturnal penile tumescence in normal males

Despite increasing clinical reliance on nocturnal penile tumescence (NPT) testing for the differential diagnosis of male impotence, little is known at present about the relationship between NPT and other aspects of sleep and waking psychophysiology. This study investigated patterns of NPT, sleep, and EEG hemispheric asymmetry in 20 male subjects, using standard polysomnographic laboratory procedures for the assessment of sleep and NPT, and a method of EEG amplitude integration developed by Goldstein. Additionally, the effects of daytime sexual activity and mood state on the duration and amplitude of NPT were studied. Overall, the results of this study confirmed the well-documented relationship between NPT and stage REM, as well as demonstrating a strong association between NPT phase and nondominant hemisphere activation. Furthermore, this association appeared to strengthen over the course of the night. Hemispheric asymmetry and stage REM were also closely linked throughout. On the other hand, no significant correlations were found between daytime sexual activity or mood state and NPT. It is suggested that concurrent assessment of hemispheric asymmetry may strengthen the diagnostic power of NPT testing in impotence cases involving central organic etiology.