What resolves this contention: Disagreement over whether mouse M1 contains a ge…

What resolves this contention: Disagreement over whether mouse M1 contains a genuine L4 equivalent; resolved by sCRACM granularity but the question of nomenclature and circuit definition remains debated in the field. / Mouse M1 contains a thin laminar zone at the L3/L5A border whose pyramidal neurons have L4-like inputs (thalamus) and largely unidirectional outputs to L2/3 — i.e. M1 has a functional L4. / Mouse vM1 long-range and local laminar circuit mapping describes M1 as organized around L2/3, L5A, L5B, and L6 layers without an L4 equivalent in the cortico-thalamo-cortical input maps.