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UBC Theses and Dissertations

Acute stress modulation of risk/reward decision-making Laino Chiavegatti, Giulio


Discerning which choices are advantageous amongst many based on reward cost or on making and withholding responses is essential for survival, and salient cues may be perceived as threatening via several neurochemical and behavioural changes. This type of decision-making where different actions may yield rewards associated with costs or punishment can be differentially altered depending on the type of costs being evaluated. In previous work from our group, we have shown acute restraint stress does not alter preference for larger/uncertain rewards vs. smaller/certain ones, but markedly shifts preference away from more physically effortful rewards. However, how stress may modulate decisions where rewards are linked to punishment has yet to be fully explored. Here we examined how different forms of acute stress influenced action-selection on two tasks involving punished reward-seeking in male and female rats. To that extent, we adopted a risky decision-making task involving choice between a small/safe lever always delivering one reward pellet and a large/risky option delivering three pellets but that could also deliver foot-shock with an increasing probability across blocks of trials (0, 25, 50, 75, 100%). In well-trained rats, one-hour restraint increased risk aversion and punishment sensitivity, markedly reducing preference for the shock-associated reward comparably between sexes. In contrast, these effects were not mimicked by either the α-2 noradrenergic antagonist yohimbine or corticosterone. In a second study a go/no-go task assessed ability to inhibit approach towards a readily available reward associated with punishment. Here, a food pellet was delivered in a cup, and on 30/60 trials the rat merely had to approach and retrieve reward. On the other 30 trials, a 12-s visual/auditory cue signalled food retrieval must be withheld to avoid foot-shock. Restraint induced an increase in impulsive action on males on test day, but females markedly less the day after, an effect that was recapitulated by yohimbine but not corticosterone. These findings suggest acute restraint enhances the effects of punishment on choice between different rewards while differentially affecting inhibitory impulse control in situation involving rewards and punishment. The mechanisms underlying this effect may relate to the increased risk aversion observed in individuals with depression.

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