UBC Theses and Dissertations
Investigating the neurobiological underpinnings and structural characteristics which contribute to biased decision making. Macfarlane Barrus, Michael
Gambling disorder (GD) and other forms of behavioural and substance addictions are characterized by deficits in decision making and impulsivity. Animal models of behaviour allow researchers to study specific components and features of biased decision making and elucidate the neural circuitry that underpins these biases. Our laboratory has developed several animal models which each examine a specific subfacet of decision making thought to contribute to GD. The rat Gambling Task examines risky decision making by posing a choice between small, safe rewards and larger but more risky options. The rat Betting Task examines a specific choice bias termed the “escalation of commitment” bias, in which humans show an increasing aversion to uncertain wagers as the amount at stake goes up. In order to examine the effect of cues on choice behaviour, we developed the Cued rat Gambling Task, which offers the same choice options as those on the rat Gambling Task, but pairs wins on the risky options with salient cues. The presence of salient environmental stimuli can influence choice behaviour, and may make important contributions to the maintenance and severity of GD. As described in this dissertation, work with these tasks has clarified the environmental, pharmacological and regional contributions to GD-like decision making. The development of the Cued rat Gambling Task demonstrated that the addition of salient cues is sufficient to drive a riskier, more disadvantageous choice preference than that demonstrated on the uncued rat Gambling Task. Disrupting orbitofrontal cortex function while the animal is learning the Cued rat Gambling Task promotes the development of a more optimal choice strategy, perhaps due to the region’s roles in cognitive flexibility and subjective valuation. Choice biases on the rat Betting Task are also ameliorated by inactivation of the orbitofrontal cortex, but not inactivation of other prefrontal regions. Furthermore, the nucleus accumbens core, but not shell, may guide the development of a risk-averse choice strategy on the rat Gambling Task. In sum, the work in this dissertation clarifies the motivational role of cues in gambling and other disorders of addiction, and elucidates the neural circuitry that underpins choice biases.
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