Cortical Connectivity and Functional Organization in Primate Brains

The primate cerebral cortex comprises a mosaic of specialised areas whose functions emerge from precise patterns of local and long-range connections. Neurons are arranged into six cortical laminae, each distinguished by characteristic cell types and densities that determine the origins and terminations of inter-areal projections. Feedforward streams, principally arising from supragranular layers, relay sensory information up the processing hierarchy, while feedback streams from infragranular layers convey contextual and modulatory signals. Architectonic properties such as laminar thickness, cell‐packing density and dendritic morphology covary systematically with connectivity profiles, reflecting evolutionary adaptations for efficient information transfer. Multi-scale approaches—combining high-resolution histology, tract‐tracing in non-human primates and computational modelling—have revealed how microcircuit diversity and large-scale organisation produce coherent dynamics underlying perception, decision making and executive control. Understanding these principles not only illuminates the biological basis of cognition but also informs translational efforts to address neurological disorders and inspires biologically grounded artificial intelligence models.

Research from Nature Portfolio

Architectonic similarity has been shown to exert a dominant influence on the existence and pattern of corticocortical projections in the primate brain. By combining quantitative measures of cytoarchitecture with spatial distance, researchers developed a predictive framework that accounts for both the presence or absence of inter-areal connections and the laminar origin of projections. This structural model achieves high accuracy in forecasting network topology and explains variations in regional connectivity strength, emphasising that the intrinsic architecture of cortical areas provides a unifying principle for organising the primate connectome.

Cortical Connectivity and Functional Organization in Primate Brains publication trend

The graph below shows the total number of articles in cortical connectivity and functional organization in primate brains across all publications each year (not limited to Nature Index journals).

Technical terms

Cortical laminae: The six horizontal layers of the neocortex, each with distinct cell types and connectivity patterns.

Supragranular layers: Layers II–III of the cortex, primarily responsible for feedforward corticocortical projections.

Infragranular layers: Layers V–VI of the cortex, chiefly involved in feedback and subcortical outputs.

Architectonic similarity: The degree of resemblance in cytoarchitectural features (cell density, laminar thickness) between cortical areas.

Feedforward pathways: Projections that transmit sensory information from lower-order to higher-order cortical regions.

Feedback pathways: Projections that send contextual or modulatory signals from higher-order to lower-order areas.

Cortico-cortical connectivity: The network of axonal projections linking different cortical regions.

Cortical hierarchy: An organisational principle arranging cortical areas in ascending order of processing complexity.

References

1. The regional variation of laminar thickness in the human isocortex is related to cortical hierarchy and interregional connectivity. PLOS Biology (2023).
2. Anatomy of hierarchy: Feedforward and feedback pathways in macaque visual cortex. The Journal of Comparative Neurology (2013).
3. A Predictive Structural Model of the Primate Connectome. Scientific Reports (2017).
4. A multi-scale layer-resolved spiking network model of resting-state dynamics in macaque visual cortical areas. PLOS Computational Biology (2018).