Cross-species functional alignment reveals evolutionary hierarchy within the connectome

Area of Science:

• Neuroscience
• Evolutionary Biology
• Comparative Anatomy

Background:

• Cortical organization and function evolve dynamically across mammalian species.
• Charting cross-species brain differences is challenging due to complex evolutionary changes in morphology and function.
• Unique human cognitive abilities may involve brain systems lacking direct anatomical counterparts in other species.

Purpose of the Study:

• To develop a function-based method for cross-species brain alignment.
• To quantify homologous cortical regions between humans and rhesus macaques, irrespective of anatomical location.
• To investigate evolutionary changes in functional organization across the mammalian cortex.

Main Methods:

• Developed a function-based approach for cross-species cortical alignment.
• Quantified homologous regions by decoupling function from anatomical landmarks.
• Analyzed functional organization gradients from unimodal to multimodal systems.

Main Results:

• Cross-species functional similarity follows a gradient, decreasing from unimodal to posterior regions.
• Most pronounced evolutionary changes were observed in the posterior default mode network (angular gyrus, posterior cingulate, middle temporal cortices).
• The default mode network shows complex evolutionary modifications, even within its subnetworks.

Conclusions:

• A function-based method enables robust cross-species homologous region identification.
• Evolutionary changes in cortical organization are not uniform, with posterior regions showing greater divergence.
• The default mode network, crucial for higher cognition, has undergone significant evolutionary alterations.