Figure 4.

Effects of amphetamine on 5CSRT performance tiered by injury severity, as determined by impact force, vs. injury susceptibility, as determined by trajectory of recovery. A) Severe-injured rats had improved attention at 1.0 mg/kg (p = 0.002), moderate-injured rats showed no change at any dose (p’s > 0.151), mild-injured rats approached impairment at 1.0 mg/kg (p = 0.052) and sham rats were impaired at the 0.6 or 1.0 mg/kg (p = 0.009; p = 0.012). B) Severe-injured rats exhibited reduced impulsivity at 1.0 mg/kg (p = 0.015), moderate-injured rats showed no change across doses (p’s > 0.128), while impulsivity increased in both mild-injured and sham rats at all doses compared to saline (p’s < 0.040). C) Overall, omissions increased at the 1.0 mg/kg dose (p = 0.004). D) In general, rats showed reduced task efficacy at all doses (p’s < 0.045). E) Susceptibility subgroups demonstrated differential effects, with resilient rats showing reduced accuracy at 1.0 mg/kg (p = 0.002), vulnerable rats showing no change at any dose (p’s > 0.137), and chronically impaired rats showing improved function at 1.0 mg/kg (p = 0.002). F) Subgroups also demonstrated similar effects with regards to impulsivity with resilient and vulnerable rats showing increased impulsivity as a function of increasing dose (p’s < 0.021) and chronically impaired rats demonstrating reduced impulsive responding at the 1.0 mg/kg dose (p = 0.012). Data shown are mean + SEM and individual data points in panels E and F, * = p < 0.05, ** = p < 0.01, ***= p < 0.001.