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Touching Helps Build the Sexual Brain

Summary: While it is widely believed social cues can accelerate puberty, previous studies have found it difficult to clearly identify the most crucial signals responsible for the change. A new study in PLOS Biology reveals sexual touch contributes to the acceleration of puberty.

Source: PLOS.

Hormones or sexual experience? Which of these is crucial for the onset of puberty? It seems that when rats are touched on their genitals, their brain changes and puberty accelerates. In a new study publishing September 21 in the open access journal PLOS Biology researchers at the Bernstein Center, and Humboldt University, Berlin, led by Constanze Lenschow and Michael Brecht, report that sexual touch might have a bigger influence on puberty than previously thought.

It has been known for some time that social cues can either accelerate or delay puberty in mammals, but it hasn’t been clear which signals are crucial, nor how they affect the body and brain, and in particular the possible reorganization of the brain.

The researchers first observed that the neural representation of the genitals in the cerebral cortex expands during puberty. To begin with, the study confirms what was expected; that sexual hormones accelerate puberty and the growth of the so-called ‘genital cortex’. However, what’s new is that they find that sexual touch also contributes substantially to the acceleration of puberty.

During their study, the scientists first put young female rats together with male rats and found that the genital cortex expanded as a result. This didn’t happen when the females were housed with other females, or if the males were separated from them by wire mesh, thereby preventing direct contact. However, they found that the same acceleration of cortical expansion could be observed when the rats’ genitals were touched artificially using a lubricated brush.

Lenschow says: “the effects of sexual touch on puberty and the genital cortex are remarkable since you wouldn’t expect this area of the brain to expand at this stage of development.” Hence, the expansion of the genital cortex is not only triggered by hormones but also by sexual touch.

Image shows a diagram of a rat brain homunculus.

This is a scheme of the somatosensory homunculus of the rat cortex. NeuroscienceNews.com image is credited to Shimpei Ishiyama.

“The representation of the body changes in the cerebral cortex,” says Brecht, “and in particular the genital cortex doubles in size. Our results help to understand why the perception of our body changes so much during puberty.” Thus, changes of the body and the concurrent changes in the brain during puberty are not merely a matter of hormones – they are also co-determined by sexual experience.

About this neuroscience research article

Funding: This research was supported by the National Institute of Environmental Health Sciences (R01ES016531, R22ES022106, and P30-ES06096) and NIH/NCRR8UL1TR000077. The researchers cite no conflicts of interest.

Source: Constanze Lenschow – PLOS
Image Source: NeuroscienceNews.com image is credited to Shimpei Ishiyama.
Original Research: Full open access research for “Development of rat female genital cortex and control of female puberty by sexual touch” by Constanze Lenschow, Johanna Sigl-Glöckner, and Michael Brecht in PLOS Biology. Published online September 21 2017 doi:10.1371/journal.pbio.2001283

Cite This NeuroscienceNews.com Article
PLOS “Touching Helps Build the Sexual Brain.” NeuroscienceNews. NeuroscienceNews, 22 September 2017.
<http://neurosciencenews.com/touch-sexual-brain-7548/>.
PLOS (2017, September 22). Touching Helps Build the Sexual Brain. NeuroscienceNews. Retrieved September 22, 2017 from http://neurosciencenews.com/touch-sexual-brain-7548/
PLOS “Touching Helps Build the Sexual Brain.” http://neurosciencenews.com/touch-sexual-brain-7548/ (accessed September 22, 2017).

Abstract

Development of rat female genital cortex and control of female puberty by sexual touch

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.

“Development of rat female genital cortex and control of female puberty by sexual touch” by Constanze Lenschow, Johanna Sigl-Glöckner, and Michael Brecht in PLOS Biology. Published online September 21 2017 doi:10.1371/journal.pbio.2001283

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