FIG. 2.

Greater injury is associated with a greater shift in cortical activation to the contralesional (right) hemisphere in response to affected (right) forelimb-evoked activation at 1 week post-injury. (A) Stacked, surface projection plot of contusion volume masked from the T2-weighted structural image of each rat at 4 weeks post-injury and warped into template space. Data shows that there are a range of injury severities within the group indicate by the presence of contusion in 11 rats (yellow region) but extending further out in only 1-5 rats (red regions). (B) Representative Jacobian maps of the same data confirming different degrees of brain injury at 4 weeks consistent with mild-to-moderate levels of brain injury (outlined region indicates the region drawn in mean deformation target image space used to obtain average Jacobian values in subject space). (C) Group-level, statistical contrast maps of affected forelimb-evoked brain activation differences between mild and moderate injured rats at 1 week post-injury (mean cortical Jacobian percentage values 0.7 ± 1.9 versus 23.8 ± 3.5%, respectively from (B) showing regions where moderate > mild group brain activation. Data show a greater left-to-right shift in the degree of cortical activation in response to affected forelimb stimulation after moderate compared with mild injury, two-tailed t-test, n = 6 vs. 5, respectively; z = 1.7, p < 0.001). (D) A linear regression analysis plot of number of activated voxels/rat in contralesional (open circles, solid line) and ipsilesional cortex (closed diamonds, dashed line) at 1 week post-injury versus injury severity (average gray matter Jacobian raw value) at 4 weeks. Data show a significantly greater contralesional (right) activation response in moderately injured rats (solid line, R² = 0.65, p < 0.05), as well as more ipsilateral activation (Dashed line, R² = 0.77, p < 0.01). Activation data after 1 week post-injury were not significantly correlated with severity (not shown). Key: Hatched circle represents approximate position of primary injured region.