Topography of Striate-Extrastriate Connections in Neonatally Enucleated Rats
Figure 1
Correlating the patterns of striate-extrastriate projections with the patterns of myelination and visual callosal connections; procedure for calculating LI. (a) Myelin pattern from a rat (BEM-2) enucleated at birth. Black arrows indicate borders of V1 and area 18a. A, auditory cortex; Sml, somatosensory cortex. White arrow indicates BDA injection site. Neighboring dark spots correspond to injections of other tracers. (b) Callosal pattern revealed following multiple injections of HRP in the contralateral hemisphere in the same enucleated rat. Dark areas correspond to dense accumulations of retrogradely labeled somas and anterogradely labeled axons. The profiles of V1, 18a, and auditory cortex were drawn from the myelin pattern in (a). Regions outlined in black represent BDA-labeled projection fields drawn from a section processed for BDA. Black dot indicates the location of the BDA injection, and the circular outline estimates the size of tracer diffusion (see Section 2). (d) Pattern of BDA-labeled projections in another enucleated rat (case M6e4). Grey dot and grey outline indicate the injection and diffusion of BDA, respectively. Border of V1, outlined in black, was determined from the callosal pattern (e) in the same case. (e) Pattern of HRP-labeled callosal connections in the same enucleated rat. Black lines in lateral extrastriate cortex outline the BDA-labeled projections shown in (d). ((c) and (f)) Diagrams illustrating the compartments (C1–C4) in area 18a used in LI calculations. The LI for each case is indicated. Line passing through injection site was used to calculate the distance from the injection site to the lateral border of V1. Inset in (a) indicates orientation, A: anterior, and L: lateral. Scale bars = 1.0 mm.
