Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Fear and avoidance are both key symptoms of several anxiety disorders, and while both terms are closely related, they are not one and the same. Fear and fear generalization may have been explored extensively in research, but only few studies have examined maladaptive avoidance in relation to fear generalization. Furthermore, people are often faced with approach-avoidance conflicts where competing rewards influence avoidance behavior. The current study tested in healthy participants an experimental paradigm for assessing (maladaptive) avoidance and instrumental generalization, in the presence versus absence of response cost (loss of symbolic points). During Pavlovian conditioning, participants learned to fear two CS+ and not to fear one CS-. Participants were then informed of a clickable button which could or could not prevent the US following a CS presentation in the avoidance phase. In this phase, participants could learn when avoidance was effective (during CSav+) and when it was not (CSnav+, CS-). During the last phase, generalization of avoidance was measured in the presence versus absence of response cost. Participants learned that avoidance was more effective in some situations compared to other situations. Competing rewards had significant effects on (maladaptive) avoidance behavior, participants showed an overall lower tendency to avoid the US in the presence of a response cost and generalized their avoidance behavior to non-effective stimuli in the absence of response cost. Participants with low distress tolerance and a high intolerance for uncertainty show more fear towards both CS+, while high anxious participants showed a greater tendency to avoid non-effective stimuli. We recommend future studies to incorporate measures for better understanding the individual value participants attribute to both US and response cost. We also believe it would be interesting to track framing effects on (generalization of) avoidance behavior by including a positive frame condition rewarding participants for non-avoidance in the current experimental paradigm.

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

According to the World Health Organization (WHO), 1 in 13 globally suffers from anxiety. Anxiety disorders are common and pervasive mental disorders, yet they are hard to treat. Lately, there has been a growing interest in the role of the microbiota-gut-brain axis in mental disorders, more specifically, in anxiety disorders. Alterations in the gut microbiota can exert influences on the gut-brain axis and one specific group of microbial metabolites, short chain fatty acids (SCFAs) are speculated to play a dominant role in this interaction. Thus, understanding these interactions may be of great importance regarding treatment and prevention. Over the past years, researches tried to manipulate mice in order to develop suitable models and make a translation to human research possible. However, the complexity of these interactions makes it very hard to translate these findings from mice to humans. This study aimed to answer the question if SCFAs could influence fear in humans. More specifically, we hypothesized a decrease in fear expression across conditioning, extinction, recall and renewal. Furthermore, we expected a decline in self-reported negative mood and distress. These hypotheses were tested in a double blind, randomized, placebo-controlled trial. A pre-posttest design with a one-week intervention of SCFAs was performed in three conditions (placebo, SCFA equivalent to 10gr of fiber, SCFAs equivalent to 20gr of fiber) during which participants adhered to a low-fiber diet. 66 healthy male participants were included in the study. The aim was to look at the physiological role of SCFAs by looking at the site of production, using colon delivery capsules. Participants engaged in a fear task on two test days, which measured fear processes such as acquisition, extinction learning, extinction recall and fear renewal. Negative mood and distress were assessed using self-reported questionnaires. Linear mixed models were used to examine if the intervention influenced the different phases and trials of fear learning across test days. Additionally, to investigate differences in subjective ratings of fear, participants’ affect ratings of the fear task were explored. This study found no evidence for the hypotheses that SCFAs can decrease fear reaction across acquisition, extinction learning, extinction recall and fear renewal in healthy humans. Furthermore, no evidence was found for a decline in self-reported mood and distress. However, translating animal models to human models is difficult for several reasons. With this study being one of the first making the translation to healthy humans, it offers useful insights for further research. Furthermore, research in animals proposed an important role for SCFAs in fear, suggesting that further research in humans should be considered.