Differential effects of environmental enrichment, social-housing, and isolation-rearing on a rat gambling task: dissociations between impulsive action and risky decision-making.

RATIONALE: Decision-making deficits, measured using the Iowa Gambling Task (IGT), are observed in many psychiatric populations. Additionally, evidence suggests that the environment also influences the development of these same disorders.
OBJECTIVE: To determine the direct influence of the environment on decision-making by utilizing the rat gambling task (rGT), a risky decision-making test modeled after the IGT.
METHODS: Male rats reared in isolation, in pairs, or in an enriched environment were trained on the rGT as adults. During the rGT, animals chose from four different options. The optimal strategy on the rGT and IGT is the same: to favor options associated with smaller immediate rewards and less punishment/loss. Impulsive action is also measured during rGT performance by recording the number of premature responses made, similar to the five-choice serial reaction time task.
RESULTS: Compared to pair-housed rats, isolated and environmentally enriched rats were slower at learning the optimal strategy. However, following training, only isolation-reared rats chose the disadvantageous options more often. Amphetamine altered decision-making on the rGT in socially housed animals, yet isolates were unaffected. Conversely, amphetamine increased premature responding similarly in all groups. This increase was attenuated by prior administration of a dopamine D(1) or D(2) antagonist; however, the ability of amphetamine to alter decision-making was not blocked by either drug.
CONCLUSIONS: Housing environment affects animals' ability to learn and perform a decision-making task. Additionally, amphetamine's effect on impulsive action appears to be mediated by the dopaminergic system, whereas its effect on risky decision-making may be mediated by other neurotransmitters.