Sexually Monomorphic Maps and Dimorphic Responses in Rat Genital Cortex

Area of Science:

• Neuroscience
• Mammalian neurobiology
• Somatosensory system

Background:

• Mammalian external genitals exhibit sexual dimorphism and are central to sexuality.
• Neural representations of genitals are poorly understood, with ongoing debate about their location in the somatosensory cortex.
• Previous studies often failed to detect distinct cortical representations for genitals.

Purpose of the Study:

• To investigate high-resolution genital representations in the mammalian somatosensory cortex.
• To explore the sexual differentiation of mammalian brains through genital neural mapping.
• To understand the somatotopic organization and characteristics of genital neural maps.

Main Methods:

• High-resolution mapping of genital representations in rat somatosensory cortex.
• Utilizing cytochrome-oxidase staining to visualize cortical layer 4 input maps for penis and clitoris.
• Analyzing neuronal responses, including multi-body-part activation and receptive field properties.

Main Results:

• Genital responses were identified in the rat somatosensory cortex, specifically in a region previously associated with arm/leg cortex.
• Genital responses were more prevalent in males than females, indicating sexual dimorphism.
• Despite response dimorphism, cortical maps of penis and clitoris input were anatomically similar (monomorphic).
• Genital representations were somatotopic, bilaterally symmetric, and increased in size during puberty.
• Cortical genital neurons exhibited unusual multi-body-part responses and sexually dimorphic receptive fields, co-activated by regions touched during mounting.

Conclusions:

• Genital representations in the somatosensory cortex are somatotopic and sexually dimorphic.
• The anatomical similarity of penis and clitoris maps suggests a deep homology and a fundamentally bisexual brain layout.
• The unique properties of cortical genital neurons indicate a role in sexually aroused states.