Fig. 3.

Quantitative correlation of in vivo fiber tracking (A and B) and ex vivo histological tracing (C and D) methods combined with statistical coregistration (E–H) in the same animals to study the somatosensory thalamocortical projection. (A) A 3D reconstruction of wild-type thalamic fiber bundles emerging from the VB nucleus of the thalamus and superimposed on the corresponding morphological MR images (as in B and C), originating at the precise location of the MiR axonal tracer injection site (see encircled area in D) and projecting into S1BF. The fibers were selected from whole-brain connectivity data generated using our global optimization algorithm. (B) PM of connectivity (scaled from 0 to 1) between VB and S1BF. The same PM is represented using the red color channel (scaled from 0 to 1) in F. Dashed lines denote the pial surface (external) and the cortical depth corresponding to the layer III/IV border (internal). (C) AD maps generated after counting the MiR-labeled axons in histological sections (normalized scale from 0 to 1: 0, no axonal labeling; 1, maximum density of labeled axons obtained in each individual). Compare with G, where the same AD map is represented using the green color channel. (D) Histological axonal tracing results showing the MiR tracer injection site localized in VB, and the cortical target regions (S1BF and S2). The exemplified histological section was used for the generation of the AD map from C and G. (E and H) Statistical coregistration of the PM (F) and the AD maps (G) of thalamocortical connectivity obtained from the same animal. Merged PM/AD maps (E) were produced showing extensive overlap of the pathways generated using the in vivo and ex vivo methodologies. Colocalized area is highlighted in H (overlap coefficient of 0.81).