Biology subjects

Lebreton, M.

Publications and source records attributed to Lebreton, M..

12 recordsLinked to original sources

bioRxiv2025

Dissociating the functional role of the para-hippocampal and the parietal cortex in human multi-step reinforcement learning

Many real-life decisions involve a tension between short-term and long-term outcomes, which requires forward-looking abilities. In reinforcement learning, this tension arises at the initial stage of multi-step learning and decision tasks, where forward-looking decisions collect smaller immediate rewards but govern the transition to more advantageous second-stage states. Here, we investigated the neural mechanisms underlying such forward-looking decisions in a cohort of healthy participants undergoing fMRI scanning (N=28). Behavioral results confirmed that participants were able to learn concurrently reward values and state-transition probabilities. By contrasting BOLD signal elicited by first-stage versus second-stage at the time of decision, we isolated a brain network, with central nodes in the bilateral parahippocampal cortex (BA37), whose activity correlate with forward-looking choices. BOLD activity in another network, including the bilateral parietal cortex, correlated with structure learning signal at the time of outcome processing. Our results shed new light on the neural bases of model-based reinforcement learning by suggesting a specific role of the parahippocampal cortex in forward planning and the parietal cortex in learning the Markovian structure of the task.

neuroscience↗

bioRxiv2023

Neural and computational underpinnings of biased confidence in human reinforcement learning

While navigating a fundamentally uncertain world, humans and animals constantly produce subjective confidence judgments, thereby evaluating the probability of their decisions, actions or statements being correct. Confidence typically correlates with neural activity positively in a ventromedial-prefrontal (VMPFC) network and negatively in a dorsolateral and dorsomedial prefrontal network. Here, combining fMRI with a reinforcement-learning paradigm, we leverage the fact that humans are more confident in their choices when seeking gains than avoiding losses to reveal a functional dissociation: whereas the dorsal prefrontal network correlates negatively with a condition-specific confidence signal, the VMPFC network positively encodes task-wide confidence signal incorporating the valence-induced bias. Challenging dominant neuro-computational models, we found that decision-related VMPFC activity better correlates with confidence than with option-values inferred from reinforcement-learning models. Altogether, these results identify the VMPFC as a key node in the neuro-computational architecture that builds global feeling-of-confidence signals from latent decision variables and contextual biases during reinforcement-learning.

animal behavior and cognition↗

bioRxiv2021

Metacognition and the effect of incentive motivation in two compulsive disorders: gambling disorder and obsessive-compulsive disorder

Compulsivity is a common phenotype amongst various psychiatric disorders, such as obsessive-compulsive disorder (OCD) and gambling disorder (GD). Deficiencies in metacognition, such as the inability to properly estimate ones own performance via well-calibrated confidence judgments could contribute to pathological decision-making in these psychiatric disorders. Earlier research has indeed suggested that OCD and GD patients reside at opposite ends of the confidence spectrum, with OCD patients exhibiting underconfidence, and GD patients exhibiting overconfidence. Recently, several studies established that motivational states (e.g. monetary incentives) influence metacognition, with gain (respectively loss) prospects increasing (respectively decreasing) confidence judgments. Here, we reasoned that the OCD and GD symptomatology might correspond to an exacerbation of this interaction between metacognition and motivational states. We hypothesized GDs overconfidence to be exaggerated during gain prospects, while OCDs underconfidence to be worsened in loss context, which we expected to see represented in ventromedial prefrontal cortex (VMPFC) blood-oxygen-level-dependent (BOLD) activity. We tested those hypotheses in a task-based functional magnetic resonance imaging (fMRI) design. Our initial analyses showed increased confidence levels for GD versus OCD patients, that could partly be explained by sex and IQ. Although our primary analyses did not support the hypothesized interaction between incentives and groups, exploratory analyses did show increased confidence in GD patients specifically in gain context. fMRI analyses confirmed a central role for VMPFC in the processing of confidence and incentives, but with no differences between the clinical samples. The trial is registered in the Dutch Trial Register (Trial NL6171, registration number: NTR6318) (https://www.trialregister.nl/trial/6171).

neuroscience↗

bioRxiv2021

A shared brain system forming confidence judgment across cognitive domains

Confidence is typically defined as a subjective judgment about whether a decision is right. Decisions are based on sources of information that come from various cognitive domains and are processed in different brain systems. An unsettled question is whether the brain computes confidence in a similar manner whatever the domain or in a manner that would be idiosyncratic to each domain. To address this issue, human participants of both sexes performed two tasks probing confidence in decisions made about the same material (history and geography statements), but based on different cognitive processes: semantic memory for deciding whether the statement was true or false, and duration perception for deciding whether the statement display was long or short. At the behavioral level, we found that the same factors (difficulty, accuracy, response time and confidence in the preceding decision) predicted confidence judgments in both tasks. At the neural level, we observed using fMRI that confidence judgments in both tasks were associated to activity in the same brain regions: positively in the ventromedial prefrontal cortex and negatively in a prefronto-parietal network. Together, these findings suggest the existence of a shared brain system that generates confidence judgments in a similar manner across cognitive domains.

neuroscience↗

bioRxiv2020

How motivational signals disrupt metacognitive signals in the human VMPFC.

A growing body of evidence suggests that, during decision-making, BOLD signal in the VMPFC correlates both with motivational variables - such as incentives and expected values - and metacognitive variables - such as confidence judgments, which reflect the subjective probability of being correct. At the behavioral level, we recently demonstrated that the value of monetary stakes bias confidence judgments, with gain (respectively loss) prospects increasing (respectively decreasing) confidence judgments, even for similar levels of difficulty and performance. If and how this value-confidence interaction is also reflected in VMPFC signals remains unknown. Here, we used an incentivized perceptual decision-making task that dissociates key decision-making variables, thereby allowing to test several hypotheses about the role of the VMPFC in the incentive-confidence interaction. While initial analyses seemingly indicate that VMPFC combines incentives and confidence to form an expected value signal, we falsified this conclusion with a meticulous dissection of qualitative activation patterns. Rather, our results show that strong VMPFC confidence signals observed in trials with gain prospects are disrupted in trials with no - or negative (loss) monetary prospects. Deciphering how decision variables are represented and interact at finer scales (population codes, individual neurons) seems necessary to better understand biased (meta)cognition.

neuroscience↗

bioRxiv2020

Investigating the origin and consequences of endogenous default options in repeated economic choices.

Classical value-based decision theories state that economic choices are solely based on the value of available options. Experimental evidence suggests, however, that individuals choices are biased towards default options, prompted by the framing of decisions. Although the effects of default options created by exogenous framing - such as how choice options are displayed - are well-documented, little is known about the potential effects and properties of endogenous framing, that is, originating from an individuals internal state. In this study, we investigated the existence and properties of endogenous default options in a task involving choices between risky lotteries. By manipulating and examining the effects of three experimental features - time pressure, time spent on task and relative choice proportion towards a specific option -, we reveal and dissociate two features of endogenous default options which bias individuals choices: a natural tendency to prefer certain types of options (natural default), and the tendency to implicitly learn a default option from past choices (learned default). Additional analyses suggest that while the natural default may bias the standard choice process towards an option category, the learned default effects may be attributable to a second independent choice process. Overall, these investigations provide a first experimental evidence of how individuals build and apply diverse endogenous default options in economic decision-making and how this biases their choices.

neuroscience↗

bioRxiv2019

Decreased confidence in loss-avoidance contexts is a primary meta-cognitive bias of human reinforcement learning

In simple instrumental-learning tasks, humans learn to seek gains and to avoid losses equally well. Yet, two effects of valence are observed. First, decisions in loss-contexts are slower, which is consistent with the Pavlovian-instrumental transfer (PIT) hypothesis. Second, loss contexts decrease individuals confidence in their choices - a bias akin to a Pavlovian-to-metacognitive transfer (PMT). Whether these two effects are two manifestations of a single mechanism or whether they can be partially dissociated is unknown. Here, across six experiments, we attempted to disrupt the PIT effects by manipulating the mapping between decisions and actions and imposing constraints on response times (RTs). Our goal was to assess the presence of the metacognitive bias in the absence of the RT bias. Were observed both PIT and PMT despite our disruption attempts, establishing that the effects of valence on motor and metacognitive responses are very robust and replicable. Nonetheless, within- and between-individual inferences reveal that the confidence bias resists the disruption of the RT bias. Therefore, although concomitant in most cases, PMT and PIT seem to be - partly - dissociable. These results highlight new important mechanistic constraints that should be incorporated in learning models to jointly explain choice, reaction times and confidence.

animal behavior and cognition↗

bioRxiv2018

How the level of reward awareness changes the computational and electrophysiological signatures of reinforcement learning

The extent to which subjective awareness influences reward processing, and thereby affects future decisions is currently largely unknown. In the present report, we investigated this question in a reinforcement-learning framework, combining perceptual masking, computational modeling and electroencephalographic recordings (human male and female participants). Our results indicate that degrading the visibility of the reward decreased -without completely obliterating- the ability of participants to learn from outcomes, but concurrently increased their tendency to repeat previous choices. We dissociated electrophysiological signatures evoked by the reward-based learning processes from those elicited by the reward-independent repetition of previous choices and showed that these neural activities were significantly modulated by reward visibility. Overall, this report sheds new light on the neural computations underlying reward-based learning and decision-making and highlights that awareness is beneficial for the trial-by-trial adjustment of decision-making strategies.\n\nSignificance statementThe notion of reward is strongly associated with subjective evaluation, related to conscious processes such as \"pleasure\", \"liking\" and \"wanting\". Here we show that degrading reward visibility in a reinforcement learning task decreases -without completely obliterating- the ability of participants to learn from outcomes, but concurrently increases subjects tendency to repeat previous choices. Electrophysiological recordings, in combination with computational modelling, show that neural activities were significantly modulated by reward visibility. Overall, we dissociate different neural computations underlying reward-based learning and decision-making, which highlights a beneficial role of reward awareness in adjusting decision-making strategies.

neuroscience↗

bioRxiv2018

Contextual influence on confidence judgments in human reinforcement learning.

The ability to correctly estimate the probability of ones choices being correct is fundamental to optimally re-evaluate previous choices or to arbitrate between different decision strategies. Experimental evidence nonetheless suggests that this metacognitive process -referred to as a confidence judgment-is susceptible to numerous biases. We investigate the effect of outcome valence (gains or losses) on confidence while participants learned stimulus-outcome associations by trial-and-error. In two experiments, we demonstrate that participants are more confident in their choices when learning to seek gains compared to avoiding losses. Importantly, these differences in confidence were observed despite objectively equal choice difficulty and similar observed performance between those two contexts. Using computational modelling, we show that this bias is driven by the context-value, a dynamically updated estimate of the average expected-value of choice options that has previously been demonstrated to be necessary to explain equal performance in the gain and loss domain. The biasing effect of context-value on confidence, also recently observed in the context of incentivized perceptual decision-making, is therefore domain-general, with likely important functional consequences.

animal behavior and cognition↗

bioRxiv2018

Reference-point centering and range-adaptation enhance human reinforcement learning at the cost of irrational preferences

In economics and in perceptual decision-making contextual effects are well documented, where decision weights are adjusted as a function of the distribution of stimuli. Yet, in reinforcement learning literature whether and how contextual information pertaining to decision states is integrated in learning algorithms has received comparably little attention. Here, in an attempt to fill this gap, we investigated reinforcement learning behavior and its computational substrates in a task where we orthogonally manipulated both outcome valence and magnitude, resulting in systematic variations in state-values. Over two experiments, model comparison indicated that subjects behavior is best accounted for by an algorithm which includes both reference point-dependence and range-adaptation - two crucial features of state-dependent valuation. In addition, we found state-dependent outcome valuation to progressively emerge over time, to be favored by increasing outcome information and to be correlated with explicit understanding of the task structure. Finally, our data clearly show that, while being locally adaptive (for instance in negative valence and small magnitude contexts), state-dependent valuation comes at the cost of seemingly irrational choices, when options are extrapolated out from their original contexts.

animal behavior and cognition↗

bioRxiv2018

Genome-wide study identifies 611 loci associated with risk tolerance and risky behaviors

Humans vary substantially in their willingness to take risks. In a combined sample of over one million individuals, we conducted genome-wide association studies (GWAS) of general risk tolerance, adventurousness, and risky behaviors in the driving, drinking, smoking, and sexual domains. We identified 611 approximately independent genetic loci associated with at least one of our phenotypes, including 124 with general risk tolerance. We report evidence of substantial shared genetic influences across general risk tolerance and risky behaviors: 72 of the 124 general risk tolerance loci contain a lead SNP for at least one of our other GWAS, and general risk tolerance is moderately to strongly genetically correlated ([Formula] to 0.50) with a range of risky behaviors. Bioinformatics analyses imply that genes near general-risk-tolerance-associated SNPs are highly expressed in brain tissues and point to a role for glutamatergic and GABAergic neurotransmission. We find no evidence of enrichment for genes previously hypothesized to relate to risk tolerance.

genetics↗

bioRxiv2017

Two sides of the same coin: monetary incentives concurrently improve and bias confidence judgments.

Decisions are accompanied by a feeling of confidence, i.e., a belief about the decision being correct. Confidence accuracy is critical, notably in high-stakes situations such as medical or financial decisionmaking. Here, we investigated how incentive motivation influences confidence accuracy by combining a perceptual task with a confidence incentivization mechanism. Importantly, by varying the magnitude and valence (gains or losses) of monetary incentives, we orthogonalized their motivational and affective components. Corroborating theories of rational decision-making and motivation, our results first reveal that the motivational value of incentives improves aspects of confidence accuracy. However, in line with a value-confidence interaction hypothesis we further show that the affective value of incentives concurrently biases confidence reports, thus degrading confidence accuracy. Finally, we demonstrate that the motivational and affective effects of incentives differentially impact how confidence builds on perceptual evidence. Altogether, these findings may provide new hints about confidence miscalibration in healthy or pathological contexts.

animal behavior and cognition↗