Sexual dimorphism in interhemispheric relations: anatomical-behavioral convergence

Area of Science:

• Neuroscience
• Human Anatomy
• Cognitive Psychology

Background:

• The embryogenetic hypothesis posits an inverse relationship between hemispheric specialization and callosal connectivity.
• Understanding interhemispheric communication is crucial for brain development and function.

Purpose of the Study:

• To test the hypothesis that hemispheric specialization is inversely related to callosal connectivity.
• To investigate potential sex differences in this relationship using anatomical and behavioral measures.

Main Methods:

• Anatomical analysis of postmortem brain tissue, correlating planum temporale asymmetry with corpus callosum morphology.
• Behavioral testing using a lateralized lexical decision task with associative primes, relating visual field advantage to corpus callosum morphometry via MRI.

Main Results:

• A significant negative correlation was found in males between planum temporale asymmetry and small fiber count in the corpus callosum isthmus.
• In males, a right visual hemifield advantage for associated words correlated negatively with the cross-sectional size of the corpus callosum isthmus.
• No significant sex differences were observed in anatomical asymmetry, behavioral asymmetry, or callosal morphology.

Conclusions:

• Convergent anatomical and behavioral evidence suggests a sexual dimorphism in human interhemispheric relations.
• The findings support an inverse relationship between hemispheric specialization and callosal connectivity, particularly in males.
• This study highlights the importance of considering sex as a biological variable in neuroscience research.