Explore the vast range of titles available.

In a volatile environment where rewards are uncertain, successful performance requires a delicate balance between exploitation of the best option and exploration of alternative choices. It has theoretically been proposed that dopamine contributes to the control of this exploration-exploitation trade-off, specifically that the higher the level of tonic dopamine, the more exploitation is favored. We demonstrate here that there is a formal relationship between the rescaling of dopamine positive reward prediction errors and the exploration-exploitation trade-off in simple non-stationary multi-armed bandit tasks. We further show in rats performing such a task that systemically antagonizing dopamine receptors greatly increases the number of random choices without affecting learning capacities. Simulations and comparison of a set of different computational models (an extended Q-learning model, a directed exploration model, and a meta-learning model) fitted on each individual confirm that, independently of the model, decreasing dopaminergic activity does not affect learning rate but is equivalent to an increase in random exploration rate. This study shows that dopamine could adapt the exploration-exploitation trade-off in decision-making when facing changing environmental contingencies.

Highly distributed neural circuits are thought to support adaptive decision-making in volatile and complex environments. Notably, the functional interactions between prefrontal and reciprocally connected thalamic nuclei areas may be important when choices are guided by current goal value or action-outcome contingency. We examined the functional involvement of selected thalamocortical and corticothalamic pathways connecting the dorsomedial prefrontal cortex (dmPFC) and the mediodorsal thalamus (MD) in the behaving rat. Using a chemogenetic approach to inhibit projection-defined dmPFC and MD neurons during an instrumental learning task, we show that thalamocortical and corticothalamic pathways differentially support goal attributes. Both pathways participate in adaptation to the current goal value, but only thalamocortical neurons are required to integrate current causal relationships. These data indicate that antiparallel flow of information within thalamocortical circuits may convey qualitatively distinct aspects of adaptive decision-making and highlight the importance of the direction of information flow within neural circuits. Planning and decision-making rely upon a region of the brain called the prefrontal cortex. But the prefrontal cortex does not act in isolation. Instead, it works together with a number of other brain regions. These include the thalamus, an area long thought to pass information on to the cortex for further processing. But signals also travel in the opposite direction, from the cortex back to the thalamus. Does the cortex-to-thalamus pathway carry the same information as the thalamus-to-cortex pathway? To find out, Alcaraz et al. blocked each pathway in rats performing a decision-making task. The rats had learned that pressing a lever led to one type of reward, whereas moving a rod led to another. Alcaraz et al. reduced the desirability of one of the rewards by giving the rats free access to it for an hour. Afterwards, the rats opted mainly for the action associated with the reward that had remained desirable. However, blocking either the thalamus-to-cortex or cortex-to-thalamus pathway prevented this preference from emerging. This suggests that an information flow in both directions is necessary to update knowledge about the value of a reward. In a second experiment, Alcaraz et al. removed the link between one of the actions and its reward. The reward instead appeared at random, irrespective of the rat’s own behavior. Control rats responded by focusing their efforts on the action that still delivered a reliable reward, and by performing the other action less often. Blocking the thalamus-to-cortex pathway prevented this response, but blocking the cortex-to-thalamus pathway did not. This suggests that only the former pathway is necessary to re-evaluate the relationship between an action and an outcome. Two key aspects of goal-directed behavior – recognizing the value of a reward and the link between an action and an outcome – thus depend differently on the thalamus-to-cortex and cortex-to-thalamus pathways. This same principle may also be at work in other neural circuits with bidirectional connections. Understanding such principles may lead to better strategies for treating disorders of brain connectivity, such as schizophrenia.

Although poor decision-making is a hallmark of psychiatric conditions such as attention deficit/hyperactivity disorder, pathological gambling or substance abuse, a fraction of healthy individuals exhibit similar poor decision-making performances in everyday life and specific laboratory tasks such as the Iowa Gambling Task. These particular individuals may provide information on risk factors or common endophenotypes of these mental disorders. In a rodent version of the Iowa gambling task--the Rat Gambling Task (RGT), we identified a population of poor decision makers, and assessed how these rats scored for several behavioral traits relevant to executive disorders: risk taking, reward seeking, behavioral inflexibility, and several aspects of impulsivity. First, we found that poor decision-making could not be well predicted by single behavioral and cognitive characteristics when considered separately. By contrast, a combination of independent traits in the same individual, namely risk taking, reward seeking, behavioral inflexibility, as well as motor impulsivity, was highly predictive of poor decision-making. Second, using a reinforcement-learning model of the RGT, we confirmed that only the combination of extreme scores on these traits could induce maladaptive decision-making. Third, the model suggested that a combination of these behavioral traits results in an inaccurate representation of rewards and penalties and inefficient learning of the environment. Poor decision-making appears as a consequence of the over-valuation of high-reward-high-risk options in the task. Such a specific psychological profile could greatly impair clinically healthy individuals in decision-making tasks and may predispose to mental disorders with similar symptoms.

In the context of Pavlovian conditioning, two types of behaviour may emerge within the population (Flagel et al. Nature, 469(7328): 53–57, 2011). Animals may choose to engage either with the conditioned stimulus (CS), a behaviour known as sign-tracking (ST) which is sensitive to dopamine inhibition for its acquisition, or with the food cup in which the reward or unconditioned stimulus (US) will eventually be delivered, a behaviour known as goal-tracking (GT) which is dependent on dopamine for its expression only. Previous work by Lesaint et al. (PLoS Comput Biol, 10(2), 2014) offered a computational explanation for these phenomena and led to the prediction that varying the duration of the inter-trial interval (ITI) would change the relative ST-GT proportion in the population as well as phasic dopamine responses. A recent study verified this prediction, but also found a rich variance of ST and GT behaviours within the trial which goes beyond the original computational model. In this paper, we provide a computational perspective on these novel results.

Purpose This study examined the contribution of work, non-work and individual factors on workers’ symptoms of psychological distress, depression and emotional exhaustion based on the multilevel determinants of workers’ mental health model. Methods Data from the SALVEO Study were collected in 2009–2012 from a sample of 1,954 employees nested in 63 workplaces in the province of Quebec (Canada). Multilevel regression models were used to analyse the data. Results Altogether, variables explain 32.2 % of psychological distress, 48.4 % of depression and 48.8 % of emotional exhaustion. Mental health outcomes varied slightly between workplaces and skill utilisation, physical and psychological demands, abusive supervision, interpersonal conflicts and job insecurity are related to the outcomes. Living in couple, having young children at home, family-to-work conflict, work-to-family conflict, strained marital and parental relations, and social support outside the workplace associated with the outcomes. Most of the individual characteristics also correlated with the three outcomes. Importantly, non-work and individual factors modulated the number and type of work factors related to the three outcomes. Conclusion The results of this study suggest expanding perspectives on occupational mental health that fully recognise the complexity of workers’ mental health determinants.

In order to select actions appropriate to current needs, a subject must identify relationships between actions and events. Control over the environment is determined by the degree to which action consequences can be predicted, as described by action-outcome contingencies--i.e. performing an action should affect the probability of the outcome. We evaluated in a first experiment adaptation to contingency changes in rats with neurotoxic lesions of the medial prefrontal cortex. Results indicate that this brain region is not critical to adjust instrumental responding to a negative contingency where the rats must refrain from pressing a lever, as this action prevents reward delivery. By contrast, this brain region is required to reduce responding in a non-contingent situation where the same number of rewards is freely delivered and actions do not affect the outcome any more. In a second experiment, we determined that this effect does not result from a different perception of temporal relationships between actions and outcomes since lesioned rats adapted normally to gradually increasing delays in reward delivery. These data indicate that the medial prefrontal cortex is not directly involved in evaluating the correlation between action--and reward--rates or in the perception of reward delays. The deficit in lesioned rats appears to consist of an abnormal response to the balance between contingent and non-contingent rewards. By highlighting the role of prefrontal regions in adapting to the causal status of actions, these data contribute to our understanding of the neural basis of choice tasks.

The relationship between personality and learning abilities has become a growing field of interest. Studies have mainly focused on the relationship with performance, such as the speed of acquisition. In this study, we hypothesised that personality could in part also be related to a certain predisposition of an individual to switch more easily from a goal-directed process to a habit process during learning. To identify these processes, we conducted a contingency degradation protocol. This study investigated 1/ whether in general horses are able to adjust their response according to the contingency between their action and the reward, 2/ whether there are any relationships between certain personality profiles and a predisposition to switch more rapidly to habitual processes, and 3/ whether emotional states experienced during the learning procedure play a role in this switching. Personality tests were conducted on 29 horses, followed by a degradation contingency protocol. Overall, results show that horses were sensitive to contingency degradation between their action and the reward. Nevertheless, there was inter-individual variability: the horses presenting high fearfulness, and to a lesser extent low sensory sensitivity and low gregariousness were less sensitive to the degradation, demonstrating that they were more likely to switch to a habitual process. Contrary to our expectations, the emotional state experienced during the procedure did not seem to explain this switching. We conclude that personality is not only related to learning performance, but also in part to the process involved during learning, independently of the emotion experienced during the process. This study provides new theoretical knowledge on cognitive skills in ungulates.

Recent computational models of sign tracking (ST) and goal tracking (GT) have accounted for observations that dopamine (DA) is not necessary for all forms of learning and have provided a set of predictions to further their validity. Among these, a central prediction is that manipulating the intertrial interval (ITI) during autoshaping should change the relative ST-GT proportion as well as DA phasic responses. Here, we tested these predictions and found that lengthening the ITI increased ST, i.e., behavioral engagement with conditioned stimuli (CS) and cue-induced phasic DA release. Importantly, DA release was also present at the time of reward delivery, even after learning, and DA release was correlated with time spent in the food cup during the ITI. During conditioning with shorter ITIs, GT was prominent (i.e., engagement with food cup), and DA release responded to the CS while being absent at the time of reward delivery after learning. Hence, shorter ITIs restored the classical DA reward prediction error (RPE) pattern. These results validate the computational hypotheses, opening new perspectives on the understanding of individual differences in Pavlovian conditioning and DA signaling.

Background Psychological distress in the workplace is usually attributed to work-related variables as well as non-work-related variables. Individuals working in the same organization can differ in terms of their appraisal of work-related stressors and coping strategies used to face them. The present study aims to evaluate the moderating role personality plays between work organizations conditions and psychological distress in a large sample of Canadian participants working in various occupations and workplaces. Methods Multilevel regression analyses were conducted on a sample that followed a hierarchical structure with workers (N1 = 1958) nested in workplaces (N2 = 63). The direct contribution of workplace and personality was tested in a variance component model as a first step. Following this initial step, we introduced interaction variables by blocks of 11. Those interaction variables refer to each interaction combined with a specific personality variable. Results Psychological demands, number of hours worked, job insecurity, neuroticism, and agreeableness were associated with higher levels of psychological distress. Inversely, decision authority, job recognition, self-esteem, locus of control were associated with lower levels of psychological distress. Lastly, agreeableness played a moderating role between low social support garnered from one’s supervisor and psychological distress. Conclusions To intervene on work-related variables, organizations could reduce psychological demands, minimize the number of hours worked through job redesign, allow teleworking and encourage work schedule flexibility. To reduce job insecurity, organizations could explicitly communicate future organizational plans. In the same vein, decision authority could be targeted by reducing hierarchical steps and increasing autonomy. Lastly, the results pertaining to agreeableness stand in contrast with those of previous studies. We assumed that workers scoring high on agreeableness tend to put themselves last and please others first. These tendencies could make them more susceptible to health issues. With that said, work environments still need workers who are agreeable and nice to be around. To prevent high levels of agreeableness leading to psychological distress, training and information workshops are recommended. Those include stress management interventions and workshops pertaining to time management and relaxation techniques.

Goal-directed behaviors are thought to be supported by a neural circuit encompassing the prefrontal cortex, the dorsomedial striatum, the amygdala, and, as more recently suggested, the limbic thalamus. Since evidence indicates that the various thalamic nuclei contribute to dissociable functions, we directly compared the functional contribution of the mediodorsal thalamus (MD) and of the anterior thalamic nuclei (ATN) in a new task assessing spatial goal-directed behavior in a cross-maze. Rats sustaining lesions of the mediodorsal or the anterior thalamus were trained to associate each of the two goal arms with a distinctive food reward. Unlike control rats, both lesioned groups failed to express a bias for the goal arm corresponding to the non-devalued outcome following devaluation by sensory-specific satiety. In addition, MD rats were slower than the other groups to complete the trials. When tested for spatial working memory using a standard non-matching-to-place procedure in the same apparatus, ATN rats were severely impaired but MD rats performed as well as controls, even when spatial or temporal challenges were introduced. Finally, all groups displayed comparable breaking points in a progressive ratio test, indicating that the slower choice performance of MD rats did not result from motivational factors. Thus, a spatial task requiring the integration of instrumental and Pavlovian contingencies reveals a fundamental deficit of MD rats in adapting their choice according to goal value. By contrast, the deficit associated with anterior thalamic lesions appears to simply reflect the inability to process spatial information.