Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Current Biology 26 (2016): 106-113, doi:10.1016/j.cub.2015.11.041.
Description:
Mammalian external genitals show sexual dimorphism [1,2] and can change size and
shape upon sexual arousal. Genitals feature prominently in the oldest pieces of figural art
[3] and phallic depictions of penises informed psychoanalytic thought about sexuality [4,
5]. Despite this longstanding interest, the neural representations of genitals are still poorly
understood [6]. In somatosensory cortex specifically, many studies did not detect any
cortical representation of genitals [7-9]. Studies in humans debate, if genitals are
represented displaced below the foot of the cortical body map [10-12], or if they are
represented somatotopically [13-15]. We wondered, what a high-resolution mapping of
genital representations might tell us about the sexual differentiation of the mammalian
brain. We identified genital responses in rat somatosensory cortex in a region previously
assigned as arm/leg cortex. Genital responses were more common in males than in
females. Despite such response dimorphism, we observed a stunning anatomical
monomorphism of cortical penis and clitoris input maps revealed by cytochrome-oxidasestaining
of cortical layer-4. Genital representations were somatotopic, bilaterally
symmetric and their relative size increased markedly during puberty. Size, shape and
erect posture give the cortical penis representation a phallic appearance pointing to a role
in sexually aroused states. Cortical genital neurons showed unusual multi-body-part
responses and sexually dimorphic receptive fields. Specifically, genital neurons were coactivated
by distant body regions, which are touched during mounting in the respective
sex. Genital maps indicate a deep homology of penis and clitoris representations in line
with a fundamentally bi-sexual layout [16] of the vertebrate brain.
Description:
This work was supported by Marine Biological Laboratory, Humboldt Universität zu Berlin
and Neurocure. M.B. was a recipient of a Gottfried Wilhelm Leibniz Prize.
Keywords:
Somatosensory cortex
;
Sexual dimorphism
;
Monomorphism
;
Genitals
;
Penis
;
Clitoris
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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