Abstract
Rat somatosensory cortex contains a large sexually monomorphic genital representation. Genital cortex undergoes an unusual 2-fold expansion during puberty. Here, we investigate genital cortex development and female rat sexual maturation. Ovariectomies and estradiol injections suggested sex hormones cause the pubertal genital cortex expansion but not its maintenance at adult size. Genital cortex expanded by thalamic afferents invading surrounding dysgranular cortex. Genital touch was a dominant factor driving female sexual maturation. Raising female rats in contact with adult males promoted genital cortex expansion, whereas contact to adult females or nontactile (audio-visual-olfactory) male cues did not. Genital touch imposed by human experimenters powerfully advanced female genital cortex development and sexual maturation. Long-term blocking of genital cortex by tetrodotoxin in pubescent females housed with males prevented genital cortex expansion and decelerated vaginal opening. Sex hormones, sexual experience, and neural activity shape genital cortex, which contributes to the puberty promoting effects of sexual touch.
Highlights
Analysis of the development of visual cortex by Hubel and Wiesel focused on binocular interactions and showed that both anatomy and physiology of ocular dominance is plastic and shaped in a visually-driven, activity-dependent process [1]
We recently identified the somatosensory representation of rat genitals; remarkably, this cortical region—genital cortex—is sexually monomorphic, despite the marked sexual dimorphism of external genitals in rats
In order to shed light on this unusual expansion, we studied genital cortex development and sexual maturation in the female rat
Summary
Analysis of the development of visual cortex by Hubel and Wiesel focused on binocular interactions and showed that both anatomy and physiology of ocular dominance is plastic and shaped in a visually-driven, activity-dependent process [1]. From work on the barrel cortex a consensus emerged that cortical input layer 4 has an earlier critical period and shows less plasticity than other cortical layers [6]. Layer 4 of rat genital cortex showed a major expansion during puberty [7]. We wondered if this very late development of genital cortex has implications for the role of activity in cortical development and might even allow early sexual experience to impact on cortical development
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