Sexually-Dimorphic Patterns of Cortical Asymmetry, and the Role for Sex Steroid Hormones in Determining Cortical Patterns of Lateralization

Cortical asymmetry varies in degree and direction. Sex differences exist for both dimensions of asymmetry: males tend to exhibit more accentuated asymmetries and stronger right hemisphere dominance compared with females, while females typically exhibit more diffuse lateralization patterns and greater left hemisphere bias compared with males. The following review considers the effects of sex steroid hormones on the sexual dimorphism of cortical lateralization patterns in human and nonhuman animals. Several excellent papers exist which consider sexual dimorphism in cortical asymmetries for morphological, physiological or functional asymmetries alone. This paper attempts to consider influences of sex steroid hormones on cortical lateralization in a framework that includes morphology, physiology and function. Converging evidence from studies that incorporate varying methodologies and theoretical backgrounds indicates that sex steroid hormones are important for influencing cortical asymmetry. Although a mechanism has not yet been identified, testosterone is the most likely candidate to influence cortical dominance.