FIG. 4.

Bilateral white matter activation is greater after moderate compared with mild injury. (A) Co-registered group-wise plots of individual, raw c-FOS+ cell positions after left-side brain injury (bold, hashed curve) after stimulation of the unaffected forelimb. Raw cell data counts are taken from three rats/group representative of mild and moderately injured rats and are overlaid onto an atlas at +1.3, -0.26, and -1.30 mm bregma, for semi-quantitative visual comparison. (B) Representative image of c-FOS+ staining from the cortical gray and white matter together with high-powered insets showing examples of c-FOS+ cells counted (white arrowheads). (C) Plot of percent hemispheric gray matter loss showing the group delineation achieved by k-means clustering of values that were assigned as mild and moderate injury and used for c-FOS group analysis in plots (A) and (D). (D) Plot of c-FOS+ cell density for gray and white matter (corpus callosum) regions for left and right hemispheres averaged from the three brain antero-posterior levels shown in (A), from mildly (n = 5) and moderately injured rats (n = 9) at 5 weeks post–traumatic brain injury showing significant difference within white matter regions (linear mixed models, Tukey's post hoc corrected, ***p < 0.001, **p < 0.01). Key: L-left, R-right. Scale bar 200 μm.