Modeling and simulation of neocortical micro- and mesocircuitry (Part I, anatomy).

Reimann, Michael W; Bolaños-Puchet, Sirio; Courcol, Jean-Denis; Egas Santander, Daniela; Arnaudon, Alexis; Coste, Benoît; Delalondre, Fabien; Delemontex, Thomas et al. · Elife · 2026

basic_science · Level V

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Abstract

The function of the neocortex is fundamentally determined by its repeating microcircuit motif, but also by its rich, interregional connectivity. We present a data-driven computational model of the anatomy of non-barrel primary somatosensory cortex of juvenile rat, integrating whole-brain scale data while providing cellular and subcellular specificity. The model consists of 4.2 million morphologically detailed neurons, placed in a digital brain atlas. They are connected by 14.2 billion synapses, comprising local, mid-range and extrinsic connectivity. We delineated the limits of determining connectivity from neuron morphology and placement, finding that it reproduces targeting by Sst+ neurons, but requires additional specificity to reproduce targeting by PV+ and VIP+ interneurons. Globally, connectivity was characterized by local clusters tied together through hub neurons in layer 5, demonstrating how local and interegional connectivity are complicit, inseparable networks. The model is suitable for simulation-based studies, and the model is made openly available to the community.

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