Males but not females report genital sensations evoked by fixed-parameter stimulation of somatosensory cortex.

Abstract

The localisation of the human genital cortex has been debated since its unusual placement in Penfield's somatosensory homunculus. While male and female genitalia are different, it remains unclear how these external differences are mapped onto the male and female brain. We investigated genital representation in the human somatosensory cortex by patient-report of sensations evoked by fixed parameter electrical stimulation during awake craniotomies. We find a reproducible genital representation in male subjects (n = 3) at the somatotopically appropriate location between the legs situated in the dorsal postcentral gyrus and sulcus. Our findings contradict early stimulation-maps derived by Penfield and colleagues, which indicated an absence of genital responses in this brain region, but align with more recent imaging data from males and females that described blood-flow responses to genital stimulation at these coordinates. Surprisingly, however, we find no evidence for stimulation-evoked genital sensations in the postcentral gyrus and sulcus of females (n = 5) in line with Penfield's earlier conclusions. Specifically, females reported no genital sensations, but often leg sensations, when stimulated at the putative coordinates of female genital cortex. We conclude that reports of genital sensations differ between male and female somatosensory cortex upon stimulation. Our observations add to the growing evidence that genital representations differ between males and females.