Monique Ernst

Neural Substrates of Reward Magnitude, Probability, and Risk During a Wheel of Fortune Decision-Making Task

Economic decision-making involves the weighting of magnitude and probability of potential gains/losses. While previous work has examined the neural systems involved in decision-making, there is a need to understand how the parameters associated with decision-making (e.g., magnitude of expected reward, probability of expected reward and risk) modulate activation within these neural systems. In the current fMRI study, we modified the monetary wheel of fortune (WOF) task [Ernst, M., Nelson, E.E., McClure, E.B., Monk, C.S., Munson, S., Eshel, N., et al. (2004). Choice selection and reward anticipation: an fMRI study. Neuropsychologia 42(12), 1585-1597.] to examine in 25 healthy young adults the neural responses to selections of different reward magnitudes, probabilities, or risks. Selection of high, relative to low, reward magnitude increased activity in insula, amygdala, middle and posterior cingulate cortex, and basal ganglia. Selection of low-probability, as opposed to high-probability reward, increased activity in anterior cingulate cortex, as did selection of risky, relative to safe reward. In summary, decision-making that did not involve conflict, as in the magnitude contrast, recruited structures known to support the coding of reward values, and those that integrate motivational and perceptual information for behavioral responses. In contrast, decision-making under conflict, as in the probability and risk contrasts, engaged the dorsal anterior cingulate cortex whose role in conflict monitoring is well established. However, decision-making under conflict failed to activate the structures that track reward values per se. Thus, the presence of conflict in decision-making seemed to significantly alter the pattern of neural responses to simple rewards. In addition, this paradigm further clarifies the functional specialization of the cingulate cortex in processes of decision-making.

Nucleus accumbens, thalamus and insula connectivity during incentive anticipation in typical adults and adolescents.

Reward neurocircuitry links motivation with complex behavioral responses. Studies of incentive processing have repeatedly demonstrated activation of nucleus accumbens (NAc), thalamus, and anterior insula, three key components of reward neurocircuitry. The contribution of the thalamus to this circuitry in humans has been relatively ignored, a gap that needs to be filled, given the central role of this structure in processing and filtering information. This study aimed to understand how these three regions function as a network during gain or loss anticipation in adults and youth. Towards this goal, functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) were used to examine effective connectivity among these three nodes in healthy adults and adolescents who performed the monetary incentive delay (MID) task. Seven connectivity models, based on anatomic connections, were tested. They were estimated for incentive anticipation and underwent Bayesian Model Selection (BMS) to determine the best-fit model for each adult and adolescent group. Connection strengths were extracted from the best-fit model and examined for significance in each group. These variables were then entered into a linear mixed model to test between-group effects on effective connectivity in reward neurocircuitry. The best-fit model for both groups included all possible anatomic connections. Three main findings emerged: (1) Across the task, thalamus and insula significantly influenced NAc; (2) A broader set of significant connections was found for the loss-cue condition than the gain-cue condition in both groups; (3) Finally, between-group comparisons of connectivity strength failed to detect statistical differences, suggesting that adults and adolescents use this incentive-processing network in a similar manner. This study demonstrates the way in which the thalamus and insula influence the NAc during incentive processing in humans. Specifically, this is the first study to demonstrate in humans the key role of thalamus projections onto the NAc in support of reward processing. Our results suggest that anticipation of gain/loss involves an alerting signal (thalamus) that converges with interoceptive information (insula) to shape action selection programs in the ventral striatum.

New perspectives on adolescent motivated behavior: Attention and conditioning

Adolescence is a critical transition period, during which fundamental changes prepare the adolescent for becoming an adult. Heuristic models of the neurobiology of adolescent behavior have emerged, promoting the central role of reward and motivation, coupled with cognitive immaturities. Here, we bring focus to two basic sets of processes, attention and conditioning, which are essential for adaptive behavior. Using the dual-attention model developed by Corbetta and Shulman (2002), which identifies a stimulus-driven and a goal-driven attention network, we propose a balance that favors stimulus-driven attention over goal-driven attention in youth. Regarding conditioning, we hypothesize that stronger associations tend to be made between environmental cues and appetitive stimuli, and weaker associations with aversive stimuli, in youth relative to adults. An attention system geared to prioritize stimulus-driven attention, together with more powerful associative learning with appetitive incentives, contribute to shape patterns of adolescent motivated behavior. This proposed bias in attention and conditioning function could facilitate the impulsive, novelty-seeking and risk-taking behavior that is typical of many adolescents.

Inhibitory control in anxious and healthy adolescents is modulated by incentive and incidental affective stimuli

BACKGROUNDnAnxiety disorders are characterized by elevated, sustained responses to threat, that manifest as threat attention biases. Recent evidence also suggests exaggerated responses to incentives. How these characteristics influence cognitive control is under debate and is the focus of the present study.nnnMETHODSnTwenty-five healthy adolescents and 25 adolescents meeting DSM-IV diagnostic criteria for an anxiety disorder were compared on a task of response inhibition. Inhibitory control was assayed with an antisaccade task that included both incentive (monetary reward) and incidental emotion (facial expression) cues presented prior to the execution of inhibitory behavior.nnnRESULTSnInhibitory control was enhanced following exposure to threat cues (fear faces) only in adolescent patients, and following exposure to positive cues (happy faces) only in healthy adolescents. Results also revealed a robust performance improvement associated with monetary incentives. This incentive effect did not differ by group. No interaction between incentives and emotional cues was detected.nnnCONCLUSIONSnThese findings suggest that biased processing of threat in anxious adolescents affects inhibitory control, perhaps by raising arousal prior to behavioral performance. The absence of normalization of performance in anxious adolescents following exposure to positive emotional cues is a novel finding and will require additional exploration. Future studies will need to more specifically examine how perturbations in positive emotion processes contribute to the symptomatology and the pathogenesis of anxiety disorders.

Longitudinal study of striatal activation to reward and loss anticipation from mid-adolescence into late adolescence/early adulthood

Adolescent risk-taking behavior has been associated with age-related changes in striatal activation to incentives. Previous cross-sectional studies have shown both increased and decreased striatal activation to incentives for adolescents compared to adults. The monetary incentive delay (MID) task, designed to assess functional brain activation in anticipation of reward, has been used extensively to examine striatal activation in both adult and adolescent populations. The current study used this task with a longitudinal approach across mid-adolescence and late adolescence/early adulthood. Twenty-two participants (13 male) were studied using the MID task at two time-points, once in mid-adolescence (mean age=16.11; SD=1.44) and a second time in late adolescence/early adulthood (mean age=20.14; SD=.67). Results revealed greater striatal activation with increased age in high- compared to low-incentive contexts (incentive magnitude), for gain as well as for loss trials (incentive valence). Results extend cross-sectional findings and show reduced striatal engagement in adolescence compared to adulthood during preparation for action in an incentive context.

Experience-dependent plasticity for attention to threat: Behavioral and neurophysiological evidence in humans

Biased attention to threat represents a key feature of anxiety disorders. This bias is altered by therapeutic or stressful experiences, suggesting that the bias is plastic. Charting on-line behavioral and neurophysiological changes in attention bias may generate insights on the nature of such plasticity. We used an attention-orientation task with threat cues to examine how healthy individuals alter their response over time to such cues. In Experiments 1 through 3, we established that healthy individuals demonstrate an increased attention bias away from threat over time. For Experiment 3, we used functional magnetic resonance imaging to determine the neural bases for this phenomenon. Gradually increasing attention bias away from threat is associated with increased activation in the occipitotemporal cortex. Examination of plasticity of attention bias with individuals at risk for anxiety disorders may reveal how threatening stimuli come to be categorized differently in this population over time.

The influence of context valence in the neural coding of monetary outcomes

The emotional significance of objects and events depends on the context in which they occur. Using functional magnetic resonance imaging, we examined the modulation of neural responses to monetary outcomes while subjects performed a decision-making task in a positive and a negative economic context. Neural responses indicated a relative regional specialization in the neural coding of outcome valence and followed three distinct patterns. The nucleus accumbens (NAc) and orbital frontal cortex (OFC) appeared to code the most extreme outcome in each context, with a potentiated response for favorable outcomes by a positive context. The amygdala and insula appeared to also code highly salient outcomes, but showed a potentiated response to unfavorable outcomes occurring in a negative context. The medial prefrontal cortex (medPFC), on the other hand, only coded favorable responses occurring in a positive context. Moreover, the medPFC showed large inter-individual variability when responding to outcomes in a negative context, suggesting that its role in a negative context may depend on a number of individual factors. The results of this work provide evidence of complex valence-based regional dissociations that are influenced by contextual factors.

Maturation cérébrale à l’adolescence : vulnérabilité comportementale

Recent neurodevelopmental research has been focusing on the transition period of adolescence into adulthood. This growing interest was spurred by the long-standing realization of the high cost of this transition period in terms of morbidity and mortality, and the emergence of research tools that permit direct examination of brain function in humans. The cost of reaching adulthood is understood as resulting from the typical behavioral and environmental changes that accompany adolescence [4]. The present review describes how the current research helps formulate neurobiological models that can be used to guide future work. One example of such a model, the triadic neural systems model [8], will be examined in more detail. This review will proceed in three stages. First, we will show how neural development results from the confluence of maturational changes that are quantitatively and qualitatively heterogeneous across brain regions, neurochemical and molecular systems. This normative developmental heterogeneity is translated into typical adolescent behavioral patterns, including risk-taking, novelty-seeking, emotional intensity and lability, and peer-group social primacy [5, 9]. Second, based on the notion that motivated behavior can be operationally decomposed into the three core modules of approach, avoidance and control, any alteration in the balance of these three core entities can affect behavior in unique ways. This formulation will serve as the foundation of the neural systems model framework proposed in this review. Third, functional neuroimaging is being used to examine how neural systems underlie this balance within the neural systems model. We will provide a summary of the state of research in this area. Finally, we will show how this research is important for understanding not only normal development, but also the psychopathology. The role of genetic or environmental factors will not be addressed here, despite their critical roles in determining and modulating the balance among the nodes of the triadic model.Recent neurodevelopmental research has been focusing on the transition period of adolescence into adulthood. This growing interest was spurred by the long-standing realization of the high cost of this transition period in terms of morbidity and mortality, and the emergence of research tools that permit direct examination of brain function in humans. The cost of reaching adulthood is understood as resulting from the typical behavioral and environmental changes that accompany adolescence 4. The present review describes how the current research helps formulate neurobiological models that can be used to guide future work. One example of such a model, the triadic neural systems model 8., will be examined in more detail. This review will proceed in three stages. First, we will show how neural development results from the confluence of maturational changes that are quantitatively and qualitatively heterogeneous across brain regions, neurochemical and molecular systems. This normative developmental heterogeneity is translated into typical adolescent behavioral patterns, including risk-taking, novelty-seeking, emotional intensity and lability, and peer-group social primacy 5, 9. Second, based on the notion that motivated behavior can be operationally decomposed into the three core modules of approach, avoidance and control, any alteration in the balance of these three core entities can affect behavior in unique ways. This formulation will serve as the foundation of the neural systems model framework proposed in this review. Third, functional neuroimaging is being used to examine how neural systems underlie this balance within the neural systems model. We will provide a summary of the state of research in this area. Finally, we will show how this research is important for understanding not only normal development, but also the psychopathology. The role of genetic or environmental factors will not be addressed here, despite their critical roles in determining and modulating the balance among the nodes of the triadic model. Language: fr

Early childhood temperament predicts substance use in young adults

Behavioral inhibition (BI) is an important early childhood marker of risk for later psychiatric problems. The current 20-year prospective, longitudinal study focused on individual differences in this early temperament and adolescent brain function. As adolescents, 83 participants initially identified in infancy with the temperament of BI were assessed using functional imaging to examine striatal responses to incentives. Five years later, as young adults, these participants provided self-report of their substance use. Our findings show that children’s early temperament interacts with their striatal sensitivity to incentives in adolescence to predict their level of substance use in young adulthood. Those young adults who, as children, showed the highest levels of BI reported the greatest substance use if, as adolescents, they also exhibited striatal hypersensitivity to incentives. These longitudinal data delineate one developmental pathway involving early biology and brain mechanisms for substance use in young adulthood.

Emotional memory in early steroid abnormalities: An fMRI study of adolescents with congenital adrenal hyperplasia

Hormonal imbalances during development may have long-lasting effects. Using functional magnetic resonance imaging (fMRI), we compared 14 youths with Congenital Adrenal Hyperplasia (CAH), a genetic disorder of hormonal dysfunction, with 22 healthy controls on memory encoding of emotional faces. Patients remembered fewer faces than controls, particularly fearful faces. FMRI data to successfully encoded fearful faces revealed that males with CAH showed significant activations in amygdala, hippocampus, and anterior cingulate relative to unaffected males, while females with CAH demonstrated deactivations relative to unaffected females in these regions. Findings indicate that steroid abnormalities during development can have important effects on neural correlates of emotional memory.