Selection of reward dimensions and risky alternatives
Action selection is thought to be implemented by corticostriatal systems. Adaptive action selection is reward-based and requires combining representations of reward with a selection mechanism. However, reward is not a unitary concept. For example, it includes motivational and hedonic dimensions. The question therefore arises how reward dimensions themselves are selected to guide reward-based behavior. For example, in some situations, the motivational reward may determine behavior whereas in others the hedonic reward dimension may be more relevant.
I will present research from my group investigating selection mechanisms neuropharmacologically and behaviorally.
In the first part of the talk, I will show that a corticostriatal gating mechanism can explain how the motivational or the hedonic reward dimension are selected to guide behavior. We find that medial and central orbitofrontal regions represent the motivational and hedonic dimensions irrespective of behavior whereas the striatum preferentially processes one or the other dimension according to current behavioral requirements. These data suggest that corticostriatal selection mechanisms may also apply to reward dimensions and thereby be more general than hitherto assumed.
In the second part of the talk, I present the findings of two interventions targeting the dopamine system with regard to risky decision making. Selecting a riskier alternative constitutes an example of choosing an alternative with higher variance but potentially higher gain within the motivational reward dimension. We find that blockade of D2/D3 receptors increases risk taking (and reduces probability distortion). Conversely, stimulating D1/D5 receptors tends to reduce risk taking (and increase loss aversion), but only in individuals with high working memory capacity. These findings reinforce the notion that the dopamine system plays a central role for risk valuation and selection of risky choice alternatives.