Fig. 1. Comparison of thalamic axons growth on surfaces coated with membrane extracts isolated from different cortical layers. (A,B) Photomicrographs of E14 thalamic explants cultured for 2 days on membranes from cortical layer 4 and cortical layer 5. The general outgrowth of thalamic explants was reduced on membranes from layer 4 (A) (which is their target substrate) compared with membranes from layer 5 (B). (C-J) Photomicrographs and schematic drawings illustrating the branching pattern of individual growing axons on layer 4 and layer 5 membrane substrates. Thalamic axons exhibit numerous side branches on membranes from their target layer (C-F) and much less on their non-target substrate (G-J). Scale bar: 100 µm in A,B; 10 µm in C-J.