Figure 5.

Tracing new patterns of neuronal connectivity in the functionally reorganized forelimb representation. A, Diagram showing the injection site of the neuronal tracer CtB and the relative anteroposterior position of coronal sections shown in B–F. B–F, Light photomicrographs showing the distribution of labeled axons and cell bodies in coronal sections, after an injection of CtB into the motor cortex of controls and after 8 weeks recovery (see white asterisks over darkly stained area in C). Insets show higher-magnification images of anterograde labeling of axons in the striatum (C) and retrograde labeling of cell bodies in the cortex (E). In general, both control and stroke recovered mice showed CtB-labeled axons and somata in the ipsilateral and contralateral M1 and M2, the primary somatosensory regions of the HL, Tr and whiskers (S1BF), S2, RS, and the Po, VM, and Re nucleus of the thalamus. Note that, 8 weeks after stroke, there is much greater CtB labeling in the ipsilateral striatum (CPu) and RS cortex, whereas labeling is reduced in more lateral cortical areas such as the HL/Tr, S1BF, and S2. G, Relative to controls, the optical density of axonal labeling in the striatum was significantly greater in the ipsilateral but not contralateral hemisphere after stroke. H, Quantification of retrogradely labeled cell bodies in stroke-recovered mice relative to controls. After stroke, there were significantly fewer labeled cell bodies in the HL/Tr, S1BF, and S2 but more labeled somata in the RS cortex. No change in cell labeling was found in the thalamic nuclei or homotopic regions of the contralateral cortex. *p < 0.05.