An Alternative to the Traditional Cold Pressor Test: The Cold Pressor Arm Wrap

Recently research on the relationship between stress and cognition, emotion, and behavior has greatly increased. These advances have yielded insights into important questions ranging from the nature of stress\u27 influence on addiction1 to the role of stress in neural changes associated with alterations in decision-making2,3. As topics being examined by the field evolve, however, so too must the methodologies involved. In this article a practical and effective alternative to a classic stress induction technique, the cold pressor test (CPT), is presented: the cold pressor arm wrap (CPAW). CPT typically involves immersion of a participant\u27s dominant hand in ice-cold water for a period of time4. The technique is associated with robust activation of the sympatho-adrenomedullary (SAM) axis (and release of catecholamines; e.g. adrenaline and noradrenaline) and mildto- moderate activation of the hypothalamic-pituitary-adrenal (HPA) axis with associated glucocorticoid (e.g. cortisol) release. While CPT has been used in a wide range of studies, it can be impractical to apply in some research environments. For example use of water during, rather than prior to, magnetic resonance imaging (MRI) has the potential to damage sensitive and expensive equipment or interfere with acquisition of MRI signal. The CPAW is a practical and effective alternative to the traditional CPT. Composed of a versatile list of inexpensive and easily acquired components, CPAW makes use of MRI-safe gelpacs cooled to a temperature similar to CPT rather than actual water. Importantly CPAW is associated with levels of SAM and HPA activation comparable to CPT, and can easily be applied in a variety of research contexts. While it is important to maintain specific safety protocols when using the technique, these are easy to implement if planned for. Creation and use of the CPAW will be discussed

Stress and Decision Making: Effects on Valuation, Learning, and Risk-taking

A wide range of stressful experiences can influence human decision making in complex ways beyond the simple predictions of a fight-or-flight model. Recent advances may provide insight into this complicated interaction, potentially in directions that could result in translational applications. Early research suggests that stress exposure influences basic neural circuits involved in reward processing and learning, while also biasing decisions toward habit and modulating our propensity to engage in risk-taking. That said, a substantial array of theoretical and methodological considerations in research on the topic challenge strong cross study comparisons necessary for the field to move forward. In this review we examine the multifaceted stress construct in the context of human decision making, emphasizing stress’ effect on valuation, learning, and risk-taking

The Effects of Acute Stress Exposure on Neural Correlates of Pavlovian Conditioning with Monetary Gains and Losses

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

Acute Stress Modulates Risk Taking in Financial Decision Making

People’s decisions are often susceptible to various demands exerted by the environment, leading to stressful conditions. Although a goal for researchers is to elucidate stress-coping mechanisms to facilitate decisionmaking processes, it is important to first understand the interaction between the state created by a stressful environment and how decisions are performed in such environments. The objective of this experiment was to probe the impact of exposure to acute stress on financial decision making and examine the particular influence of stress on decisions with a positive or negative valence. Participants’ choices exhibited a stronger reflection effect when participants were under stress than when they were in the nostress control phase. This suggests that stress modulates risk taking, potentially exacerbating behavioral bias in subsequent decision making. Consistent with dual-process approaches, decision makers fall back on automatized reactions to risk under the influence of disruptive stress

The Effects of Acute Stress on Human Prefrontal Working Memory Systems

We examined the relationship between acute stress and prefrontal-cortex (PFC) based working memory (WM) systems using behavioral (Experiment 1) and functional magnetic resonance imaging (fMRI; Experiment 2) paradigms. Subjects performed a delayed-response item-recognition task, with alternating blocks of high and low WM demand trials. During scanning, participants performed this task under three stress conditions: cold stress (induced by cold-water hand-immersion), a room temperature water control (induced by tepid-water hand-immersion), and no-water control (no hand-immersion). Performance was affected by WM demand, but not stress. Cold stress elicited greater salivary cortisol readings in behavioral subjects, and greater PFC signal change in fMRI subjects, than control conditions. These results suggest that, under stress, increases in PFC activity may be necessary to mediate cognitive processes that maintain behavioral organization

Evidence for Multiple Manipulation Processes in Prefrontal Cortex

The prefrontal cortex (PFC) is known to subserve working memory (WM) processes. Brain imaging studies of WM using delayed response tasks (DRTs) have shown memory-load-dependent activation increases in dorsal prefrontal cortex (PFC) regions. These activation increases are believed to reflect manipulation of to-be-remembered information in the service of memory-consolidation. This speculation has been based on observations of similar activation increases in tasks that overtly require manipulation by instructing participants to reorder to-be-remembered list items. In this study, we tested the assumption of functional equivalence between these two types of WM tasks. Participants performed a DRT under two conditions with memory loads ranging from 3 to 6 letters. In an “item-order” condition, participants were required to remember letters in the order in which they were presented. In a “reordering” condition, participants were required to remember the letters in alphabetical order. Load-related activation increases were observed during the encoding and maintenance periods of the order maintenance condition, whereas load-related activation decreases were observed in the same periods of the reordering condition. These results suggest that (1) the neural substrates associated with long-list retention and those associated with reordering are not equivalent, (2) cognitive processes associated with long-list retention may be more closely approximated by item-order maintenance than by reordering, and (3) multiple forms of WM manipulation are dissociable on the basis of fMRI data

Reward Processing in the Human Brain: Insights from fMRI

Reward processing engages diverse brain regions, including multiple prefrontal regions and the basal ganglia (particularly the multifaceted striatum). Corticostriatal circuits are involved in computation of subjective value for experienced rewards, leading to a valuation signal that can be used to guide future decisions via reinforcement-learning mechanisms. In recent years, an explosion of neuroimaging research has replicated and extended findings from a rich body of animal literature on basic brain reward systems to probe how such systems are modulated by more complex processes that typically influence goal-directed behavior in human society. The goal of this chapter is to discuss the integration of neuroimaging studies of reward processing, with emphasis on cortical-striatal circuits involved in goal-directed behavior and the valuation of reward-related information. Neuroimaging research highlights functional subdivisions within components of this corticostriatal circuitry. Reward processing can be modulated by a number of additional factors, including magnitude of reward, risk, time, and social context. Furthermore, the chapter highlights how cortical-striatal circuits and valuation signals can be modulated by the presence of more complex factors such as risk, time, and social context. Important directions for future research include the study of the complex modulation of reward processing by social factors, as well as processing of aversive information that can also modulate behavior

Interactions between acute stress and financial decision-making

Day-to-day decision-making is susceptible to various demands exerted by the environment. At times, such demands can lead to stressful conditions, affecting both psychological and physiological states. In order for researchers to understand how to control stressful conditions while making informed goal-oriented decisions, a necessary first step is to probe the interaction between the state created by exposure to acute stress and how decisions are performed under those conditions. To that end, the goal of this dissertation is to elucidate the effects of acute stress on decision-making at both the behavioral and neural levels. This will be accomplished by focusing on three aspects of the relationship between stress and decision-making. First, the question of how acute stress alters financial decisions during a financial decision-making task similar to those used in the fields of neuroeconomics will be addressed. The second will be an examination of whether or not the effects of acute stress generalize to other types of more automatized decision-making tasks -- in this case, a task involving instrumental conditioning. Finally, the neural systems underlying the potential interaction between acute stress and financial decision-making will be considered.Ph.D.Includes bibliographical references (p. 102-115)by Anthony J. Porcell

Acute Stress Enhances Expression of Instrumentally Conditioned Financial Preferences

Background: Recent research suggests acute stress exposure can be associated with increased habit-based over goal-oriented decision-making. To date, research has focused on use of primary reinforcers (e.g., food) in devaluation-type experimental designs (e.g., Schwabe and Wolf, 2009, 2011). The current study examined if acute stress might also promote expression of habit-based decision-making using secondary reinforcers. Namely, simple financial preferences “overtrained” to habit. Methods: Over three days participants were instrumentally conditioned to discriminate between simple visual stimuli probabilistically associated with monetary gains/losses. They then chose between pairs of stimuli for actual financial outcomes. On the fourth day after an acute stress or control procedure, participants performed the same learning and decision tasks during fMRI scanning, followed by two similar tasks in which monetary values associated with the stimuli were reversed. Results: Participants in both groups successfully acquired stimuli contingencies; they to reliably chose the “better” option when presented with pairs of overtrained stimuli from Days 1 to 3 (reaching asymptote on Day 2), as well as on Day 4 prior to reversal. After reversal, acutely stressed participants made significantly more decisions consistent with original stimuli values despite that these were now financially detrimental. Thus, acutely stressed participants made more decisions consistent with their original overtrained preferences. In controls, at learning differential BOLD responses associated with stimuli valence were observed in regions associated with goal-directed and habit-based behaviors for both overtrained and post-reversal stimulus-outcome pairings. In the acute stress group, similar differential BOLD signals were limited to the putamen and only for overtrained pairings. During decision-making, increased BOLD was observed in dorsal anterior cingulate cortex and insula for “poor” versus “good” decisions in both groups. Further, stress-related alterations in dorsolateral prefrontal and entorhinal cortices were observed during decision-making. Conclusions: The current study adds to research that demonstrates a propensity to rely on habitual behavior after exposure to acute stress, and that this may generalize to include also secondary reinforcers. Further, these findings suggest stress-induced neural changes take place during both the acquisition of stimuli contingencies and retrieval of reward-related information used to guide decision-making

To trust, or not to trust? Individual differences in physiological reactivity predict trust under acute stress.

The stress response represents an evolutionarily ancient array of biological responses to challenge or threat that facilitate survival by promoting adaptive behaviors. \u27Adaptive\u27 in the evolutionary sense, however, does not easily translate to explain stress\u27 effect on human decisions. Much research demonstrates that acute stress alters decision-making, but outcomes are obscured by a range of methodological factors. Further, less is known about how stress affects decision-making in social contexts in which people so often act. This is of great importance in today\u27s increasingly complex social environment, replete with potential stressors, where cooperation and trust are critical. Here the aim was to explore acute stress\u27 effect on prosocial decision-making, while also controlling for methodological factors that may contribute to varied research outcomes. Ninety-six participants were exposed between-subjects to acute stressors with or without a significant social evaluative component, or a control procedure, after which they performed a variant of the Trust Game (a social decision-making task requiring cooperation and trust with a \u27partner\u27). Task performance occurred at different times with respect to exposure to examine the roles of temporally distinct biological stress pathways. Overall acute stress was associated with reduced trust, but a more complex pattern emerged when accounting for individual differences in physiological stress responses via multivariate analysis. In keeping with the complexity of stress itself, acute stress may enhance or reduce propensity to trust based on an individual\u27s unique pattern of physiological reactivity