Robust sex differences in functional brain connectivity are present in utero

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Brain Imaging

Background:

• Sex-based differences in brain structure and function are observed throughout development.
• These differences are linked to variations in behavior, cognition, and neurodevelopmental disorder presentation.
• Early identification of sex-based brain differences is crucial for understanding developmental trajectories.

Purpose of the Study:

• To identify sex-dependent differences in functional brain connectivity in human fetuses.
• To determine if these differences are reliable enough for sex classification prior to birth.
• To investigate the nature of fetal brain connectivity patterns associated with sex.

Main Methods:

• Utilized resting-state functional magnetic resonance imaging (fMRI) on 110 human fetal scans (95 fetuses, 19-40 gestational weeks).
• Employed multiple support vector machine (SVM) models for a data-driven assessment of sex differences.
• Identified reliable features (functional connections) differentiating fetal sex across SVM models.

Main Results:

• Functional brain connectivity patterns accurately classified fetal sex with 73% accuracy.
• Key predictive connections involved somatomotor, frontal areas, hippocampus, cerebellum, and basal ganglia.
• Females showed a greater magnitude of cross-region connections, while males exhibited predominantly within-region connections.

Conclusions:

• Sex-based brain differences are present and reliably detectable before birth.
• These prenatal differences are consistent and identifiable, mirroring patterns observed later in development.
• Findings highlight the early emergence of sex differentiation in the human brain.