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UBC Theses and Dissertations

Investigating the neurobiological basis of decision-making using a novel rat gambling task Zeeb, Fiona Dawn


The Iowa Gambling Task (IGT) is a commonly used clinical test of decision-making. During the IGT, subjects choose between options associated with gains and losses. We have developed a novel rat gambling task (rGT), during which subjects are required to maximize their earnings within a 30 min session. Animals choose between four options, each associated with a different number of sucrose pellets, probability of receiving reward, and the magnitude and possibility of experiencing a punishing time-out period during which reward cannot be earned. Persistent choice of the larger reward options results in greater loss—as these options are associated with more frequent and longer time-out periods—resulting in less reward earned per unit time. Therefore, similar to the IGT, subjects are required to choose from the smaller reward options to maximize long-term gains. Results from Experiment 1 demonstrated that rats learn to choose most often from the best option by incorporating multiple factors into making their decisions. Therefore, the rGT may be a useful tool to study the biological basis of decision-making. Following pharmacological challenges with amphetamine and receptor-specific serotonergic and dopaminergic agents, data from Experiments 1 and 2 demonstrated that both neurotransmitters play important roles in modulating decision-making preferences. Furthermore, results from Experiment 2 suggested that amphetamine’s ability to alter decision-making may not be caused by increased dopamine release. Additionally, animals reared in an enriched environment or in isolation were slower to learn the optimal strategy, but only isolation-reared rats chose more often from the disadvantageous options. Experiment 3 determined that lesions of either orbitofrontal cortex (OFC) or basolateral amygdala (BLA) impaired acquisition of the rGT. However, if these lesions occurred after training on the rGT, only rats with BLA lesions chose disadvantageously. These results indicated that the BLA—but not the OFC—is involved in maintaining an optimal strategy on the rGT, yet both regions are required during task acquisition. Experiment 4 used a contralateral disconnection lesion procedure to determine that the connectivity between the OFC and BLA was important in learning the optimal strategy, as well as updating decision-making preferences following reward devaluation.

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