Structured and target-specific development of cortico-cortical connectivity in the mouse visual cortex.

V1 cortico-cortical projection neurons develop precise, target-specific connections through early establishment of distinct subtypes, not by exuberant growth and pruning, in mice.

• Why it matters: Understanding how specific long-range cortical connections form is crucial for deciphering brain wiring principles, yet the developmental mechanisms remain unclear, hindering insights into neural circuit formation.
• What they did: The study mapped postnatal development of V1 to eleven higher visual areas in mice using retrograde, anterograde, and single-cell tracing, revealing staggered axon growth aligned with target positions.
• The result: Findings show individual V1 neurons maintain specific projection motifs from early stages, enabling targeted refinement, which advances our understanding of how precise cortical networks are assembled.