Figure 4

Ectopic INCs ten days after early enucleation. (A1-A5, B1-B5, C1-C5, D1-D5, E1-E5) Rostral to caudal series of 100 μm coronal sections of P10 hemispheres following placement of DiA or DiI crystals in putative visual or somatosensory cortices to label INCs and (A6-E6) flattened reconstructions of DPLs and INCs in control and enucleated brains. In the representative control brain, retrogradely labeled cells from a DPL in the parietal somatosensory cortex are found rostral and caudal to the DPL (green labeling in A1-A3) and do not overlap with cells or axons labeled by an occipital visual cortex DPL (red labeling in A3). The arrow in A3 indicates the region of non-overlap between the labeling fields of the two areas, which represents the medial S-V areal boundary at P10. In brains from enucleated mice, retrogradely labeled cells from the somatosensory DPL are found rostral and caudal to the DPL (green labeling in B1-B3, C1-C3, D1-D3, E1-E3). Labeled cells are also found in more medial positions not seen in controls, resulting in an overlap with cells labeled by a visual DPL (regions at and below arrows in B3, C3, D3, E3). This extension of the green label in B3, C3, D3, E3 (arrows) may represent a shift of the medial S-V boundary. These retrogradely labeled green cells project to the somatosensory DPL, and are present in a region normally devoted to visual cortex. This shift of the medial boundary of somatosensory cortex is illustrated in the lateral view reconstructions in B6, C6, D6, E6 (compare boxed regions and their magnified insets in B6, C6, D6, E6 with boxed region and inset in A6 where no overlap exists). Colored regions in reconstructions: green: somatosensory DPL; red: visual DPL; small green dots: retrogradely labeled cells from parietal somatosensory DPL; small red dots: retrogradely labeled cells from occipital visual DPL; rectangular boxes: highlight S-V border region, magnified in inset. In rostral (left) to caudal (right) serial sections, dorsal is up and medial is to the left. In the reconstructions, medial (M) is up and rostral (R) is to the left. Scale bars = 1,000 μm. Asterisks indicates DPL. DiA: 4-(4-(dihexadecylamino)styryl)-N-methylpyridinium iodide; DiI: 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate; DPL: dye placement location; INC: ipsilateral intraneocortical connection; P: postnatal day; s: somatosensory areas; S-V: somatosensory-visual; v: visual cortex.