Exposure to uncertainty mediates the effects of traumatic brain injury on probabilistic decision-making in rats.

: Traumatic brain injury (TBI) is associated with numerous psychiatric comorbidities, and subclinical psychiatric symptoms. While many symptoms have been replicated in animal models of brain injury, a vast majority of studies utilize naïve rats as subjects, which fail to mimic the complex learning history of human patients. : In the current study, we evaluated the effects of a brain injury in animals with early exposure to uncertainty on post-injury decision-making in a probabilistic task, the rodent gambling task (RGT). : Exposure to uncertainty resulted in a heterogeneous sample relative to prior publications, and brain-injured rats showed no deficits in choice behavior compared to shams which contrasts with large, pervasive deficits in previously published work. However, TBI increased impulsivity and caused transient changes in behavioral variables indicative of initial motivational deficits (pellets earned, omitted responses). Notably, effects of amphetamine were similar on this heterogeneous sample of rats relative to a number of other published reports, suggesting consistent effects of gross monoaminergic manipulations on choice behavior, independent of experience. : Going forward, translational studies need to consider the heterogeneity that exists at the clinical level and account for these problems when modeling diseases in animals.