The mammalian cerebral cortex is the seat of high-level cognitive processes that allow a high degree of behavioral flexibility. It is characterized by a laminar organization, broadly conserved across mammalian species, that defines its cytoarchitecture.
Neuroanatomical studies have focused on identifying cytoarchitectural features that distinguish different cortical areas to map function onto structure.
This framework has been successful with primary sensory regions. It has been complemented and complicated by human imaging studies that highlight additional organizational principles, distributed networks, and continuous gradients, which do not always align with areal boundaries.

Recent work in rodents has likewise shown that gradients of cell type, connectivity, and function can define networks that cut across cytoarchitectural divisions. Together with transcriptomic atlases (e.g., the Allen Brain Atlas, BICCN), connectivity-based parcellations and gradient analyses in human imaging, and evidence for hierarchical timescales across the cortex, these advances point to a view in which discrete and continuous descriptions of cortical organization coexist.

A central open question follows: are areas and gradients alternative descriptions of the same underlying biology, or do they capture distinct organizational principles that interact to shape cortical computation?
A related question is whether and how canonical microcircuit motifs are themselves modulated along these gradients to support the diversity of functions performed across the cortical sheet.

A growing body of work also suggests that disruptions to this multi-layered organization contribute to neurological and psychiatric disease. Compressed functional gradients have been reported in autism, altered cortical hierarchies and microcircuit imbalance in schizophrenia, and connectivity-guided spread of pathology in Alzheimer’s disease and other tauopathies. Integrating gradient-, area-, and circuit-level views may therefore be clinically as well as conceptually informative.

This Research Topic aims to explore the different levels of cortical organization, drawing on studies of cell type distribution, gene expression gradients, connectivity, and function as measured by imaging or neurophysiology.
To address this biological question, we welcome articles contributing to the following, but not limited to, themes:

• Distribution of cell types in the cortex.
• Spatial biology of the cortex.
• Connectivity-based cortical organization.
• Cortical organization described by gene expression across the cortex.
• Developmental origin of gradients of cell types and functions.
• Functional gradients described through imaging or neurophysiology at the single-cell or population level.
• Description of canonical circuit functions across cortical regions.
• Computational modelling of anatomical and functional gradients.
• Implications of anatomical and functional gradients for neurological and psychiatric disorders.

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Biogeography of the cortex: anatomical and functional levels of cortical organization in health and disease