Extended Data Fig. 1: The EC stream of migratory neurons extends medially from the temporal lateral ventricle as a multilayered lamina along the anterior–posterior axis.

a, Three orientations of the cleared tissue block in Fig. 1a stained with TOPRO and imaged using a light-sheet microscope. Dense chains emerging from the ventricle can be seen escaping from the ventricle in horizontal view (arrowheads). Reconstruction of the EC stream is shown from a ventral view facing anterior-medially. b, Immunostained sections of the EC stream at birth showing dense clusters of DCX⁺PSA-NCAM⁺ cells. c, Map at 10 days postnatal showing the location of insets (1–2) with a cross section of DAB immunostained PSA-NCAM⁺ cell clusters. Boxes 3 and 4 show a location next to the ventricle with DAB immunostained PSA-NCAM⁺ cells in a continuous layer next to the ventricle and in distinct clusters at varying distances from the ventricle. d, Map at birth of DCX⁺PSA-NCAM⁺ cell clusters in a coronal series of sections of the medial temporal lobe. Clusters distributed along a medial-lateral orientation are present ventral to the basolateral amygdala between the EC and medial temporal gyrus (i-iv). The EC stream (arrow) is visible from the first section containing the temporal lobe ventricle and at every section examined posteriorly across the hippocampus (iii-viii). Note at levels iii and iv an additional laterally oriented migratory stream (green arrowhead). e, TEM of immature neurons in the human EC stream at birth showing densely packed neurons (red, N) with compacted chromatin and fusiform morphology (inset), astrocytes (blue, A) and microglia (yellow, M). Scale bars: 1 mm (a, d), 100 µm (b left panels, c 3, 4), 20 µm (c 1,2), 10 µm (b right 1,2), 2 µm (e). Abbreviations: BLA basolateral amygdala; EC: entorhinal cortex; FuG: fusiform gyrus; HP: hippocampus; ITG: inferior temporal gyrus; MTG: medial temporal gyrus, STG: superior temporal gyrus; sub: subiculum; tLV: temporal lobe lateral ventricle.