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

Neural Systems Underlying Aversive Conditioning in Humans with Primary and Secondary Reinforcers

Money is a secondary reinforcer commonly used across a range of disciplines in experimental paradigms investigating reward learning and decision-making. The effectiveness of monetary reinforcers during aversive learning and associated neural basis, however, remains a topic of debate. Specifically, it is unclear if the initial acquisition of aversive representations of monetary losses depends on similar neural systems as more traditional aversive conditioning that involves primary reinforcers. This study contrasts the efficacy of a biologically defined primary reinforcer (shock) and a socially defined secondary reinforcer (money) during aversive learning and its associated neural circuitry. During a two-part experiment, participants first played a gambling game where wins and losses were based on performance to gain an experimental bank. Participants were then exposed to two separate aversive conditioning sessions. In one session, a primary reinforcer (mild shock) served as an unconditioned stimulus (US) and was paired with one of two colored squares, the conditioned stimuli (CS+ and CS−, respectively). In another session, a secondary reinforcer (loss of money) served as the US and was paired with one of two different CS. Skin conductance responses were greater for CS+ compared to CS− trials irrespective of type of reinforcer. Neuroimaging results revealed that the striatum, a region typically linked with reward-related processing, was found to be involved in the acquisition of aversive conditioned response irrespective of reinforcer type. In contrast, the amygdala was involved during aversive conditioning with primary reinforcers, as suggested by both an exploratory fMRI analysis and a follow-up case study with a patient with bilateral amygdala damage. Taken together, these results suggest that learning about potential monetary losses may depend on reinforcement learning related systems, rather than on typical structures involved in more biologically based fears

Avoiding Negative Outcomes: Tracking the Mechanisms of Avoidance Learning in Humans During Fear Conditioning

Previous research across species has shown that the amygdala is critical for learning about aversive outcomes, while the striatum is involved in reward-related processing. Less is known, however, about the role of the amygdala and the striatum in learning how to exert control over emotions and avoid negative outcomes. One potential mechanism for active avoidance of stressful situations is postulated to involve amygdala–striatal interactions. The goal of this study was to investigate the physiological and neural correlates underlying avoidance learning in humans. Specifically, we used a classical conditioning paradigm where three different conditioned stimuli (CS) were presented. One stimulus predicted the delivery of a shock upon stimulus offset (CS+), while another predicted no negative consequences (CS−). A third conditioned cue also predicted delivery of a shock, but participants were instructed that upon seeing this stimulus, they could avoid the shock if they chose the correct action (AV+). After successful learning, participants could then easily terminate the shock during subsequent stimulus presentations (AV−). Physiological responses (as measured by skin conductance responses) confirmed a main effect of conditioning, particularly showing higher arousal responses during pre (AV+) compared to post (AV−) learning of an avoidance response. Consistent with animal models, amygdala–striatal interactions were observed to underlie the acquisition of an avoidance response. These results support a mechanism of active coping with conditioned fear that allows for the control over emotional responses such as fears that can become maladaptive and influence our decision-making

Regulating the expectation of reward via cognitive strategies

Previous emotion regulation research has been successful in altering aversive emotional reactions. It is unclear, however, whether such strategies can also efficiently regulate expectations of reward arising from conditioned stimuli, which can at times be maladaptive (for example, drug cravings). Using a monetary reward-conditioning procedure with cognitive strategies, we observed attenuation in both the physiological (skin conductance) and neural correlates (striatum) of reward expectation as participants engaged in emotion regulation. The expectation of a potential reward elicits positive feelings and aids in the learning of environmental cues that predict future rewards. Central to this process is the role of the striatum, a multifaceted structure that is involved in affective learning and general reward processing across species 1-3 , which is particularly engaged when potential rewards are predicted or anticipated 4-6 . However, this striatum signal can also be maladaptive and correlates with drug specific cravings 7 , potentially increasing urges to partake in risk-seeking behavior 8 . Given this, it is important to understand how to regulate or control the positive feelings associated with reward expectation. One promising method for examining this is the utilization of cognitive strategies commonly used in both social 9 and clinical 8 disciplines. Emotion regulation strategies, for example, have been successful in attenuating aversive emotional reactions that are elicited by various types of negative stimuli 10 , a pattern that is also reflected in neural regions involved in emotion, such as the amygdala, with both behavioral and subcortical neural modulations possibly mediated by prefrontal cortical regions Fifteen participants who gave written consent were presented with an adapted version of a classical conditioning procedure that has been previously used to study aversive learning 13 . Specifically, participants were presented for 4 s with two conditioned stimuli, a blue and a yellow square, that either predicted (CS+) or did not predict (CS-) a potential monetary reward ($4.00; We obtained written informed consent from 15 participants before the experiment. A repeated-measures ANOVA with the SCRs revealed a main effect of type of conditioned stimuli (CS+, CS-; F 1,14 ¼ 15.48, P o 0.001), a main effect of type of instruction (attend, regulate; F 1,14 ¼ 14.75, P o 0.002) and an interaction between the two factors (F 1,14 ¼ 23.51, P o 0.0001; The second contrast (regulate versus attend trials) yielded a variety of cortical regions that have been previously implicated in emotion regulation Our finding that emotion regulation strategies can successfully modulate physiological and neural correlates underlying the expectation of reward in a conditioning procedure is a first step to understanding how top-down modulation may effectively control positive emotions and eventual urges that may arise (for example, drug craving). This is consistent with recent neuroimaging studies suggesting that cognitive strategies modulate subcortical regions involved in aversive emotional processin

Thermodynamic study of the solubility of sodium naproxen in some ethanol + water mixtures

By using the van't Hoff and Gibbs equations the apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for sodium naproxen in ethanol + water cosolvent mixtures, were evaluated from solubility data determined at temperatures from (278.15 to 308.15) K. The drug solubility was greatest in neat water and lowest in neat ethanol at all the temperatures studied. By means of non-linear enthalpy-entropy compensation analysis, it follows that the dissolution process of this drug in ethanol-rich mixtures is entropy-driven, whereas, in water-rich mixtures the process is enthalpy-driven

A Reward-Based Framework of Perceived Control

Perceived control can be broadly defined as the belief in one’s ability to exert control over situations or events. It has long been known that perceived control is a major contributor toward mental and physical health as well as a strong predictor of achievements in life. However, one issue that limits a mechanistic understanding of perceived control is the heterogeneity of how the term is defined in models in psychology and neuroscience, and used in experimental settings across a wide spectrum of studies. Here, we propose a framework for studying perceived control by integrating the ideas from traditionally separate work on perceived control. Specifically, we discuss key properties of perceived control from a reward-based framework, including choice opportunity, instrumental contingency, and success/reward rate. We argue that these separate reward-related processes are integral to fostering an enhanced perception of control and influencing an individual’s behavior and well-being. We draw on select studies to elucidate how these reward-related elements are implicated separately and collectively in the investigation of perceived control. We highlight the role of dopamine within corticostriatal pathways shared by reward-related processes and perceived control. Finally, through the lens of this reward-based framework of perceived control, we consider the implications of perceived control in clinical deficits and how these insights could help us better understand psychopathology and treatment options

MODELAMIENTO TERMOCINEMÁTICO 3D DE LA HISTORIA DE EXHUMACIÓN DEL SECTOR DE GUAYABETAL, KM 58 VÍA BOGOTÁ – VILLAVICENCIO: RELACIONES ENTRE CLIMA, RELIEVE Y TECTÓNICA

Las interacciones -clima-tectónica pueden dar lugar a cambios topográficos significativos tanto por aumentos en la elevación como por el incremento de pendientes. Estos cambios, en conjunción con la acción de la gravedad suscitan a su vez diferencias en la energía potencial de materiales geológicos (rocas, agua, etc.) desencadenando procesos geomórficos importantes tales como la erosión por agua, tanto laminar como concentrada, y los movimientos en masa En la vía Bogotá-Villavicencio en el kilómetro 58 del municipio de Guayabetal, se han presentado numerosos fenómenos de remoción en masa. La presente investigación explora como operan las interacciones entre el clima y la tectónica como procesos controladores del relieve actual a corto y largo plazo sobre la zona de estudio. Con esta finalidad se compilaron edades termocronológicas existentes en la zona, y se generó un modelo directo termocinemático 3D para estimar los pulsos y las tasas de exhumación. Los resultados de este último sugieren 3 pulsos de exhumación: el primero entre 40 Ma - 25 Ma a una tasa de exhumación de 0,5 km/Ma, seguido de un pulso entre 25 Ma - 15 Ma con una tasa de 0,1 km/Ma, y finalmente, desde 15 Ma al presente tasas de ~2 km/Ma. Adicionalmente, datos de precipitación fueron utilizados para estimar atributos primarios y secundarios del terreno, mientras que los datos de sismicidad instrumental fueron empleados para calcular la deformación sísmica, energía sísmica y levantamiento vertical por deformación sísmica. Las distintas variables fueron comparadas estadísticamente. Se concluye que el paisaje actual de la zona no es afectado uniformemente por la tectónica y las precipitaciones. En el noroccidente del área existen bajas tasas de erosión y actividad tectónica, así la evolución del paisaje es más pasiva, y el relieve es controlado por el patrón de precipitaciones. En contraste, hacia el suroriente específicamente entre macizo de Quetame y el piedemonte llanero, el relieve es controlado por la tectónica presente en el área. El efecto antrópico con las modificaciones al paisaje introducidas por la creación de una vía nacional, aunque es importante no fue analizado en la presente investigación