Stable long-range interhemispheric coordination is supported by direct anatomical projections.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Comparative Neurology

Background:

• Interhemispheric communication relies on connections between the brain's two hemispheres.
• Homotopic connections, linking corresponding regions, are known for their exceptional strength compared to heterotopic connections.
• Previous research indicated homotopic functional connectivity (FC) is stable over time.

Purpose of the Study:

• To investigate the stability of homotopic functional connectivity (FC) across different conditions.
• To test if strong and stable homotopic FC is underpinned by structural connectivity.
• To compare the stability of homotopic FC with intrahemispheric and heterotopic connections.

Main Methods:

• Comparative analysis of functional connectivity (FC) in humans and macaques.
• Assessment of FC stability across varying experimental conditions.
• Examination of the relationship between temporal FC stability and underlying structural connectivity, including callosal axon properties.

Main Results:

• Interhemispheric FC between homotopic regions was significantly stronger in both humans and macaques.
• Homotopic FC demonstrated the greatest stability across conditions, showing more resistance to change than other connection types.
• Homotopic FC exhibited significantly higher temporal stability, facilitated by direct anatomical projections and influenced by callosal axon properties along the anterior-posterior axis.

Conclusions:

• Homotopic functional connectivity is notably stable across conditions and over time.
• The corpus callosum plays a crucial role in maintaining stable functional communication between brain hemispheres.
• Structural connectivity, particularly direct anatomical projections, significantly contributes to the temporal stability of homotopic FC.