Sexual dimorphisms of the brain

Area of Science:

• Neurobiology
• Reproductive Biology
• Developmental Biology

Background:

• The concept of sexual differentiation of the brain has evolved significantly, impacting reproductive biology and animal behavior.
• Mammalian brains are fundamentally female, with male characteristics influenced by testicular hormones.
• Research into the mechanisms of hormonal action on brain development has been complex due to limited model systems.

Purpose of the Study:

• To review the development and evolution of the concept of sexual brain differentiation.
• To explore the hormonal mechanisms underlying brain sexual differentiation.
• To highlight the significance of structural correlates like the sexually dimorphic nucleus of the preoptic area (SDN-POA).

Main Methods:

• Historical review of research on sexual brain differentiation.
• Examination of the role of testicular hormones, particularly estradiol, in masculinization.
• Investigation of the sexually dimorphic nucleus of the preoptic area (SDN-POA) as a model system.

Main Results:

• Estradiol, derived from testosterone, is identified as a key hormone in masculine brain differentiation.
• The sexually dimorphic nucleus of the preoptic area (SDN-POA) serves as a morphological marker for gonadal hormone action.
• Hormonal promotion of neuronal survival during developmental cell death is a proposed mechanism for sexual differentiation.

Conclusions:

• The mammalian brain's sexual differentiation is primarily driven by testicular hormones, with estradiol playing a crucial role.
• The SDN-POA provides a valuable model for studying the fundamental mechanisms of hormone action on brain development.
• Comparative approaches using different animal species are essential for future research into brain sexual differentiation.