title: Sexually Monomorphic Maps and Dimorphic Responses in Rat Genital Cortex.
abstract: 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 whether genitals are represented displaced below the foot of the cortical body map [10-12] or whether 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-oxidase-staining of cortical layer 4. Genital representations were somatotopic and 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 co-activated 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.
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Bernstein Center for Computational Neuroscience Berlin, Humboldt-Universität zu Berlin, Philippstrasse 13, Haus 6, 10115 Berlin, Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Lenschow
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Department of Biology, Case Western Reserve University, 2080 Adelbert Road, Room 108, Cleveland, OH 44106, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Copley
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Division of Natural Sciences, New College of Florida, 5800 Bayshore Road, Sarasota, FL 34243-2109, USA.
authors.forename: Jayne M
authors.initials: JM
authors.lastname: Gardiner
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Graduate Program of Neuroscience and Physiology, New York University School of Medicine, 522 First Avenue, Smilow, Room 501, New York, NY 10016, USA.
authors.forename: Zoe N
authors.initials: ZN
authors.lastname: Talbot
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Suite 506, Bronx, NY 10461, USA.
authors.forename: Ariel
authors.initials: A
authors.lastname: Vitenzon
authors.affiliation: Neural Systems and Behavior, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Bernstein Center for Computational Neuroscience Berlin, Humboldt-Universität zu Berlin, Philippstrasse 13, Haus 6, 10115 Berlin, Germany. Electronic address: michael.brecht@bccn-berlin.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Brecht
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D002987:Clitoris / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D008297:Male; D009474:Neurons / Q000502:physiology; D010413:Penis / Q000033:anatomy & histology / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D012611:Scrotum / Q000033:anatomy & histology / Q000502:physiology; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D014110:Touch; D014844:Vulva / Q000033:anatomy & histology / Q000502:physiology
keywords: clitoris; genitals; monomorphism; penis; sexual dimorphism; somatosensory cortex