What resolves this contention: Conflicting view of the L5→L2/3 ascending pathwa…

What resolves this contention: Conflicting view of the L5→L2/3 ascending pathway's role: a developmentally critical driver of the canonical circuit (neonatal) versus a sparse adult input. / In neonatal mouse barrel cortex, L2/3 pyramidal neurons receive significant L5 inputs during the first postnatal week, and silencing L5 disrupts L4→L2/3 connectivity — establishing a L5→L2/3 translaminar dependence that precedes the mature feedforward microcircuit. / In adult mouse C2 barrel column, the layer-pair P(conn) matrix shows ascending L5→L2/3 as rare relative to the dominant L4→L2/3 input — there is no functional dependence of L4→L2/3 on L5 outputs in the adult connectivity description.