Structural connectivity of the human massa intermedia: A probabilistic tractography study

Area of Science:

• Neuroanatomy
• Human Connectomics
• Neuroimaging

Background:

• The function of the massa intermedia (MI) in human neurocognition remains unclear.
• Previous research links MI absence to psychiatric disorders, suggesting a role in normal brain function.
• Emerging evidence indicates MI is a midline white matter tract facilitating interhemispheric connectivity.

Purpose of the Study:

• To investigate the structural connectivity of the massa intermedia (MI) in the human brain.
• To identify gray matter regions connected by the MI.
• To explore potential sex differences in MI-mediated connectivity.

Main Methods:

• Utilized the Human Connectome Project database to identify MI presence in an unrelated sample.
• Generated MI structural connectivity maps using whole-brain probabilistic tractography.
• Identified gray matter target regions connected to the MI.

Main Results:

• Probabilistic tractography revealed extensive MI connections with limbic, frontal, and temporal lobes, insula, and pericalcarine cortices.
• A significant finding was stronger MI connectivity in women compared to men.
• The MI demonstrated robust connectivity with the amygdala, hippocampus, and entorhinal cortex.

Conclusions:

• The findings support the massa intermedia's role as a crucial midline commissure.
• The MI facilitates significant interhemispheric communication, especially with limbic structures involved in emotion and memory.
• Sex-based differences in MI connectivity warrant further investigation into neurodevelopment and function.