Abstract
Pavlovian conditioning involves the association of an inherently neutral stimulus with an appetitive or aversive outcome, such that the neutral stimulus itself acquires reinforcing properties. Across species, this type of learning has been shown to involve subcortical brain regions such as the striatum and the amygdala. It is less clear, however, how the neural circuitry involved in the acquisition of Pavlovian contingencies in humans, particularly in the striatum, is affected by acute stress. In the current study, we investigate the effect of acute stress exposure on Pavlovian conditioning using monetary reinforcers. Participants underwent a partial reinforcement conditioning procedure in which neutral stimuli were paired with high and low magnitude monetary gains and losses. A between-subjects design was used, such that half of the participants were exposed to cold stress while the remaining participants were exposed to a no stress control procedure. Cortisol measurements and subjective ratings were used as measures of stress. We observed an interaction between stress, valence, and magnitude in the ventral striatum, with the peak in the putamen. More specifically, the stress group exhibited an increased sensitivity to magnitude in the gain domain. This effect was driven by those participants who experienced a larger increase in circulating cortisol levels in response to the stress manipulation. Taken together, these results suggest that acute stress can lead to individual differences in circulating cortisol levels which influence the striatum during Pavlovian conditioning with monetary reinforcers.
Highlights
Pavlovian conditioning, a fundamental learning mechanism, involves the acquisition of an association between a neutral conditioned stimulus (CS) and an unconditioned stimulus (US) such that the CS acquires the properties of the US
SUBJECTIVE STRESS RATINGS Post-experimental subjective ratings of perceived stress experience were examined between acute stress and no stress experimental groups via planned independent t-tests
Female participants were screened for use of oral contraceptives that might influence cortisol levels
Summary
A fundamental learning mechanism, involves the acquisition of an association between a neutral conditioned stimulus (CS) and an unconditioned stimulus (US) such that the CS acquires the properties of the US. Numerous laboratory studies have examined the behavioral and neural bases of this process in the absence of external environmental factors, highlighting the involvement of structures such as the striatum, amygdala and medial prefrontal cortex during acquisition (for review see Everitt and Robbins, 2005; Phelps and LeDoux, 2005; Peters et al, 2009; Schiller and Delgado, 2010). While this phenomenon has been well-characterized in the literature, less is known about how inherently negative states, such as those induced by stress, can impact the neural circuits underlying the acquisition of Pavlovian contingencies. The goal of the current study was to examine the effect of acute stress on the neural correlates of Pavlovian conditioning using monetary gains and losses
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