A developmental stretch-and-fill process that optimises dendritic wiring

Circuit connectivity and computation depend on how dendrites branch and occupy space within neural tissue. While optimal wiring principles have long been known to constrain dendritic morphology and their scaling behaviour, the growth dynamics that produce such optimised structures remain unclear. Leveraging structural imaging across development, we identify two complementary growth strategies - inside-out versus outside-in - that together generate mature dendritic arbours. We formalise these dynamics in a mathematical model that captures the two growth modes and show that their interplay yields wiring-efficient, space-filling morphologies and class-specific developmental trajectories across species. This framework provides an algorithmic account of how local branching dynamics give rise to globally optimised architectures. By linking dendritic growth rules to functional design constraints, our theory offers a unifying description of dendritic differentiation and a basis for understanding how coverage and connectivity emerge during neural circuit formation. In briefWe derive a detailed mathematical model that describes long-term time-lapse data of growing dendrites; it optimises total wiring and space-filling. HighlightsO_LIFly neurons stretch and fill a given target area with precise scaling relations. C_LIO_LIWe observe a sequence of two growth strategies. C_LIO_LIEach growth type implements optimal wiring which leads to optimal space filling. C_LIO_LIA model combining these programs captures the development of dendritic structures. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/191064v2_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1f2aed5org.highwire.dtl.DTLVardef@1b449edorg.highwire.dtl.DTLVardef@161a400org.highwire.dtl.DTLVardef@1562be5_HPS_FORMAT_FIGEXP M_FIG C_FIG