Mapping the complex web of connections within the macaque brain

Health · Published 20 October 2026 Swipe more like this →

In short: Researchers mapping the macaque cerebral cortex identified 1,615 interareal pathways using retrograde tracer injections in 29 specific brain areas. The study revealed that one-third of these pathways had never been reported before. By analyzing these connections, the team created a weighted and directed matrix to describe how different regions of the cortex communicate with one another.

The study found that most projections in the brain follow a lognormal distribution, meaning the majority are relatively weak or moderate in strength. Interestingly, while the newly discovered pathways were weaker on average than previously known ones, their weight distributions overlapped significantly. The research also highlighted an unexpectedly high number of unidirectional links within the cortex.

This mapping provides a structural blueprint for understanding cortical networks. However, the study was limited by only injecting tracers into 29 of the 91 total areas, meaning the full connectivity of all regions remains partially incomplete.

Why it matters: Mapping the brain's physical wiring helps scientists understand how different regions coordinate to produce complex behaviors.

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