Pain in context: the effect of goal competition on pain-related fear and avoidance

The Fear-Avoidance model proposes that pain-related fear and avoidance behavior play a key role in the maintenance and exacerbation of chronic pain problems. Both experimental and clinical studies have widely corroborated this model. However, there remain some unresolved issues that warrant further scientific scrutiny. One of the challenges is that pain (behavior) does not occur in a motivational vacuum, but that the goal to avoid pain interacts with other, often competing goals. It is argued that fear-avoidance models would benefit from the inclusion of a motivational perspective. The main aim of this dissertation was to experimentally investigate the impact of goal competition on pain-related fear and avoidance behavior. Additionally, we studied the presence and experience of goal conflict in a clinical population. For this purpose, a series of experiments building on a well-established differential fear conditioning paradigm, the Voluntary Joystick Movement Paradigm, was developed. In a typical experiment, healthy participants completed movements in different directions. Some of these movements were associated with painful electrocutaneous stimuli, whereas other movements were not. Likewise, movements could be associated with reward—in the form of lottery tickets—or the loss thereof. Experiment I.1 (N=55) demonstrated that presenting a concurrent reward attenuated avoidance behavior, but did not alter pain-related fear. Experiment I.2 (N=57) corroborated these findings, and additionally demonstrated that these effects were modulated by goal prioritization. Experiment II.1 (N=48) showed that avoidance-avoidance competition installed more fear and slowed down decision-making compared to other types of competition. Experiment III.1 (N=46) showed that cues predicting a painful outcome increased pain-related fear as well as avoidance behavior, and installed competition when combined with a movement that was associated with reward. Experiment III.2 (N=42) demonstrated that although pain avoidance was prominent, a pain cue was associated with less pain-avoidance behavior than a neutral or reward cue. To address the second aim of this dissertation, patients with fibromyalgia (N=40) and healthy, matched controls (N=37) participated in a semi-structured interview mapping the presence of goal conflicts (Study IV.1). More than half of the patients reported that pain control or avoidance goals conflict with other goals, such as household activities or social activities. This dissertation provides novel experimental evidence for the inclusion of a broad motivational perspective in the Fear-Avoidance model, and may also help improve the effectiveness of existing cognitive-behavioral treatments for patients suffering from chronic pain by addressing goal competition.status: publishe

Goal conflict in chronic pain : day reconstruction method

Background When suffering from chronic pain, attempts to control or avoid pain often compete with other daily activities. Engaging in one activity excludes engaging in another, equally valued activity, which is referred to as “goal conflict.” As yet, the presence and effects of goal conflicts in patients with chronic pain remain poorly understood. Methods This study systematically mapped the presence and experience of goal conflicts in patients with fibromyalgia compared to healthy controls. A total of 40 patients and 37 controls completed a semi-structured interview in which they first reconstructed the previous day, identified conflicts experienced during that day, and classified each of the conflicting goals in one of nine goal categories. Additionally, they assessed how they experienced the previous day and the reported conflicts. Results Results showed that patients did not experience more goal conflicts than healthy controls, but that they did differ in the type of conflicts experienced. Compared to controls, patients reported more conflicts related to pain, and fewer conflicts involving work-related, social or pleasure-related goals. Moreover, patients experienced conflicts as more aversive and more difficult to resolve than control participants. Discussion This study provides more insight in the dynamics of goal conflict in daily life, and indicates that patients experience conflict as more aversive than controls, and that conflict between pain control (and avoidance) and other valued activities is part of the life of patients

The exploration-exploitation dilemma in pain:an experimental investigation

ABSTRACT: Daily life consists of a chain of decisions. Typically, individuals may choose to pursue what they already know (exploitation), or to search for other options (exploration). This exploration-exploitation dilemma is a topic of interest across multiple scientific fields. Here we propose that investigating how individuals solve this dilemma may improve our understanding of how individuals make behavioral decisions (e.g., avoidance) when facing pain. To this end, we present the data of three experiments in which healthy individuals were given the opportunity to choose between four different movements, with each movement being associated with different probabilities of receiving a painful outcome only (Experiment 1), or pain and/or a reward (Experiment 2). We also investigated whether participants stuck to their decisions when the contingencies between each movement and the painful/rewarding outcome changed during the task (Experiment 3). The key findings across all experiments are the following: First, after initial exploration, participants most often exploited the safest option. Second, participants weighted rewards more heavily than receiving pain. Lastly, after receiving a painful outcome, participants were more inclined to explore than to exploit a rewarding movement. We argue that by focusing more on how individuals in pain solve the exploration-exploitation dilemma is helpful in understanding behavioral decision-making in pain

Corrosion protection of Cu by atomic layer deposition

Atomic layer deposition (ALD) is a vapor phase technique that is able to deposit uniform, conformal thin films with an excellent thickness control at the atomic scale. 18 nm thick Al2O3 and TiO2 coatings were deposited conformaly and pinhole-free onto micrometer-sized Cu powder, using trimethylaluminum and tetrakis(dimethylamido)titanium(IV), respectively, as a precursor and de-ionized water as a reactant. The capability of the ALD coating to protect the Cu powder against corrosion was investigated. Therefore, the stability of the coatings was studied in solutions with different pH in the range of 0-14, and in situ raman spectroscopy was used to detect the emergence of corrosion products of Cu as an indication that the protective coating starts to fail. Both ALD coatings provide good protection at standard pH values in the range of 5-7. In general, the TiO2 coating shows a better barrier protection against corrosion than the Al2O3 coating. However, for the most extreme pH conditions, pH 0 and pH 14, the TiO2 coating starts also to degrade. Published by the AVS

Plasmonic near-field localization of silver core-shell nanoparticle assemblies via wet chemistry nanogap engineering

Silver nanoparticles are widely used in the field of plasmonics because of their unique optical properties. The wavelength-dependent surface plasmon resonance gives rise to a strongly enhanced electromagnetic field, especially at so-called hot spots located in the nanogap in-between metal nanoparticle assemblies. Therefore, the interparticle distance is a decisive factor in plasmonic applications, such as surface-enhanced Raman spectroscopy (SERS). In this study, the aim is to engineer this interparticle distance for silver nanospheres using a convenient wet-chemical approach and to predict and quantify the corresponding enhancement factor using both theoretical and experimental tools. This was done by building a tunable ultrathin polymer shell around the nanoparticles using the layer-by-layer method, in which the polymer shell acts as the separating interparticle spacer layer. Comparison of different theoretical approaches and corroborating the results with SERS analytical experiments using silver and silver polymer core shell nanoparticle clusters as SERS substrates was also done. Herewith, an approach is provided to estimate the extent of plasmonic near-field enhancement both theoretically as well as experimentally

Competing goals attenuate avoidance behavior in the context of pain

Current fear-avoidance models consider pain-related fear as a crucial factor in the development of chronic pain. However, pain-related fear often occurs in a context of multiple, competing goals. This study investigated whether pain-related fear and avoidance behavior are attenuated when individuals are faced with a pain avoidance goal and another valued but competing goal, operationalized as obtaining a monetary reward. Fifty-five healthy participants moved a joystick toward different targets. In the experimental condition, a movement to one target (conditioned stimulus [CS+]) was followed by a painful unconditioned stimulus (pain-US) and a rewarding unconditioned stimulus (reward-US) on 50% of the trials, whereas the other movement (nonreinforced conditioned stimulus [CS)) movement was not. In the control condition, the CS+ movement was followed by the pain-US only. Results showed that pain-related fear was elevated in response to the CS+ compared to the CS movement, but that it was not influenced by the reward-US. Interestingly, participants initiated a CS+ movement slower than a CS movement in the control condition but not in the experimental condition. Also, in choice trials, participants performed the CS+ movement more frequently in the experimental than in the control condition. These results suggest that the presence of a valued competing goal can attenuate avoidance behavior. Perspective: The current study provides experimental evidence that both pain and competing goals impact on behavioral decision making and avoidance behavior. These results provide experimental support for treatments of chronic pain that include an individual's pursuit of valuable daily life goals, rather than limiting focus to pain reduction only. (C) 2014 by the American Pain Societ

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

[EN] Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal-polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.This work was supported by grant PID2019-111772RB-I00 funded by MCIN/AEI/10.13039/501100011033 and grant IT 1254-19 funded by Basque Government. The authors acknowl- edge the financial support of the European Commission (EUSMI, Grant 731019). S.B. is grateful to the European Research Council (ERC-CoG-2019 815128). The authors acknowledge the contributions by Dr. Adrian Pedrazo Tardajos related to sample support and electron microscopy experiments