Neural Mechanisms Behind Identification of Leptokurtic Noise and Adaptive Behavioral Response.

Large-scale human interaction through, for example, financial markets causes ceaseless random changes in outcome variability, producing frequent and salient outliers that render the outcome distribution more peaked than the Gaussian distribution, and with longer tails. Here, we study how humans cope with this evolutionary novel leptokurtic noise, focusing on the neurobiological mechanisms that allow the brain, 1) to recognize the outliers as noise and 2) to regulate the control necessary for adaptive response. We used functional magnetic resonance imaging, while participants tracked a target whose movements were affected by leptokurtic noise. After initial overreaction and insufficient subsequent correction, participants improved performance significantly. Yet, persistently long reaction times pointed to continued need for vigilance and control. We ran a contrasting treatment where outliers reflected permanent moves of the target, as in traditional mean-shift paradigms. Importantly, outliers were equally frequent and salient. There, control was superior and reaction time was faster. We present a novel reinforcement learning model that fits observed choices better than the Bayes-optimal model. Only anterior insula discriminated between the 2 types of outliers. In both treatments, outliers initially activated an extensive bottom-up attention and belief network, followed by sustained engagement of the fronto-parietal control network.

The human brain encodes event frequencies while forming subjective beliefs.

To make adaptive choices, humans need to estimate the probability of future events. Based on a Bayesian approach, it is assumed that probabilities are inferred by combining a priori, potentially subjective, knowledge with factual observations, but the precise neurobiological mechanism remains unknown. Here, we study whether neural encoding centers on subjective posterior probabilities, and data merely lead to updates of posteriors, or whether objective data are encoded separately alongside subjective knowledge. During fMRI, young adults acquired prior knowledge regarding uncertain events, repeatedly observed evidence in the form of stimuli, and estimated event probabilities. Participants combined prior knowledge with factual evidence using Bayesian principles. Expected reward inferred from prior knowledge was encoded in striatum. BOLD response in specific nodes of the default mode network (angular gyri, posterior cingulate, and medial prefrontal cortex) encoded the actual frequency of stimuli, unaffected by prior knowledge. In this network, activity increased with frequencies and thus reflected the accumulation of evidence. In contrast, Bayesian posterior probabilities, computed from prior knowledge and stimulus frequencies, were encoded in bilateral inferior frontal gyrus. Here activity increased for improbable events and thus signaled the violation of Bayesian predictions. Thus, subjective beliefs and stimulus frequencies were encoded in separate cortical regions. The advantage of such a separation is that objective evidence can be recombined with newly acquired knowledge when a reinterpretation of the evidence is called for. Overall this study reveals the coexistence in the brain of an experience-based system of inference and a knowledge-based system of inference.

Activity in inferior parietal and medial prefrontal cortex signals the accumulation of evidence in a probability learning task.

In an uncertain environment, probabilities are key to predicting future events and making adaptive choices. However, little is known about how humans learn such probabilities and where and how they are encoded in the brain, especially when they concern more than two outcomes. During functional magnetic resonance imaging (fMRI), young adults learned the probabilities of uncertain stimuli through repetitive sampling. Stimuli represented payoffs and participants had to predict their occurrence to maximize their earnings. Choices indicated loss and risk aversion but unbiased estimation of probabilities. BOLD response in medial prefrontal cortex and angular gyri increased linearly with the probability of the currently observed stimulus, untainted by its value. Connectivity analyses during rest and task revealed that these regions belonged to the default mode network. The activation of past outcomes in memory is evoked as a possible mechanism to explain the engagement of the default mode network in probability learning. A BOLD response relating to value was detected only at decision time, mainly in striatum. It is concluded that activity in inferior parietal and medial prefrontal cortex reflects the amount of evidence accumulated in favor of competing and uncertain outcomes.

Decision making: how the brain weighs the evidence.

The brain has to weigh incoming sensory evidence against prior beliefs, the relative weight given to each depending on the relative uncertainties. Neuroscience now shows how the human brain accomplishes this.

Neural correlates of risk prediction error during reinforcement learning in humans.

Behavioral studies have shown for decades that humans are sensitive to risk when making decisions. More recently, brain activities have been shown to be correlated with risky choices. But an important gap needs to be filled: How does the human brain learn which decisions are risky? In cognitive neuroscience, reinforcement learning has never been used to estimate reward variance, a common measure of risk in economics and psychology. It is thus unknown which brain regions are involved in risk learning. To address this question, participants completed a decision-making task during fMRI. They chose repetitively from four decks of cards and each selection was followed by a stochastic payoff. Expected reward and risk differed among the decks. Participants' aim was to maximize payoffs. Risk and reward prediction errors were calculated after each payoff based on a novel reinforcement learning model. For reward prediction error, the strongest correlation was found with the BOLD response in the striatum. For risk prediction error, the strongest correlation was found with the BOLD responses in the insula and inferior frontal gyrus. We conclude that risk and reward prediction errors are processed by distinct neural circuits during reinforcement learning. Additional analyses revealed that the BOLD response in the inferior frontal gyrus was more pronounced for risk aversive participants, suggesting that this region also serves to inhibit risky choices.

Neurobiological studies of risk assessment: a comparison of expected utility and mean-variance approaches.

When modeling valuation under uncertainty, economists generally prefer expected utility because it has an axiomatic foundation, meaning that the resulting choices will satisfy a number of rationality requirements. In expected utility theory, values are computed by multiplying probabilities of each possible state of nature by the payoff in that state and summing the results. The drawback of this approach is that all state probabilities need to be dealt with separately, which becomes extremely cumbersome when it comes to learning. Finance academics and professionals, however, prefer to value risky prospects in terms of a trade-off between expected reward and risk, where the latter is usually measured in terms of reward variance. This mean-variance approach is fast and simple and greatly facilitates learning, but it impedes assigning values to new gambles on the basis of those of known ones. To date, it is unclear whether the human brain computes values in accordance with expected utility theory or with mean-variance analysis. In this article, we discuss the theoretical and empirical arguments that favor one or the other theory. We also propose a new experimental paradigm that could determine whether the human brain follows the expected utility or the mean-variance approach. Behavioral results of implementation of the paradigm are discussed.

Cognitive deficits and biases for food and body in bulimia: investigation using an affective shifting task.

OBJECTIVE: Studies suggest that attentional deficits and biases play a role in the development and maintenance of eating disorders. Many of these studies have methodological limitations and their results are difficult to interpret. In this study, we examine attentional deficits and biases in bulimia. METHOD: 18 bulimic participants and 18 controls performed an adaptation of the go/no-go affective shifting task. That task allows the investigation of attention, inhibitory control and mental flexibility for stimuli related to the body and food. RESULTS: Bulimic participants tended to react faster than controls in the go/no-go affective task. They also had poorer discrimination ability than controls and showed inhibition problems, particularly when the targets were related to food. The magnitude of these effects ranged from moderate to large. No difference between groups was found concerning mental flexibility. DISCUSSION: These results suggest that bulimics present cognitive deficits and are more impulsive, especially with food-related stimuli. These cognitive deficits and biases may be at least partially responsible for the development and maintenance of bulimia.

Heterogeneous inhibition processes involved in different facets of self-reported impulsivity: evidence from a community sample.

Whiteside and Lynam (Whiteside, S. P., & Lynam, D. R. (2001). The Five Factor Model and impulsivity: Using a structural model of personality to understand impulsivity. Personality and Individual Differences, 30, 669-689) clarified the multifaceted nature of impulsivity by identifying four distinct facets of self-reported impulsive behaviors: urgency, (lack of) premeditation, (lack of) perseverance, and sensation seeking. Building on work by Bechara and Van der Linden (Bechara, A., & Van der Linden, M. (2005). Decision-making and impulse control after frontal lobe injuries. Current Opinion in Neurology, 18, 734-739), the main objective of this study was to investigate the hypothesis that perseverance and urgency map onto the two distinct inhibitory functions distinguished by Friedman and Miyake (Friedman, N. P., & Miyake, A. (2004). The relations among inhibition and interference control functions: A latent-variable analysis. Journal of Experimental Psychology: General, 133, 101-135): prepotent response inhibition and resistance to proactive interference. Participants (N=126) completed the UPPS Impulsive Behavior Scale and three tasks: a recent-negatives task to assess proactive interference in working memory, and two Go/No-Go tasks at different paces, the slower of which also assessed task-unrelated thoughts (TUTs). Consistent with the hypothesis, TUTs were positively correlated with lack of perseverance, and multiple regressions revealed that urgency was specifically related to errors in prepotent response inhibition, and lack of perseverance to errors due to difficulties overcoming proactive interference.

Assessing impulsivity changes in Alzheimer disease.

Impulsive behaviors are common in brain-damaged patients including those with neurodegenerative diseases such as Alzheimer disease (AD). The objective of this study was to develop and validate a short version of the UPPS Impulsive Behavior Scale assessing changes on 4 different dimensions of impulsivity, namely urgency, (lack of) premeditation, (lack of) perseverance, and sensation seeking, arising in the course of a neurodegenerative disease. To this end, caregivers of 83 probable AD patients completed a short questionnaire adapted from the UPPS Impulsive Behavior Scale. Exploratory and confirmatory factor analyses of the data were performed and revealed that a model with 4 distinct but related latent variables corresponding to 4 different dimensions of impulsivity fit the data best. Furthermore, the results showed that lack of perseverance, followed by lack of premeditation and urgency, increased after the onset of the disease, whereas sensation seeking decreased. Overall, the multifaceted nature of impulsivity was confirmed in a sample of AD patients, whose caregivers reported significant changes regarding each facet of impulsivity. Consequently, the short version of the UPPS Impulsive Behavior Scale opens up interesting prospects for a better comprehension of behavioral symptoms of dementia.

Alcohol cues increase cognitive impulsivity in individuals with alcoholism.

BACKGROUND: Individuals with alcoholism are characterized by both attentional bias for alcohol cues and prepotent response inhibition deficit. We tested the hypothesis that alcoholics exhibit greater cognitive disinhibition when the response to be suppressed is associated with alcohol-related information. METHODS: Forty recently detoxified individuals with alcoholism were compared with 40 healthy non-substance abusers on the "Alcohol-Shifting Task", a variant of the go/no-go paradigm requiring a motor response to targets and no response to distracters. The aim was to test the ability of alcoholics to discriminate between alcohol-related and neutral words. Sometimes, the alcohol-related words were the targets for the "go" response, with neutral words as distracters, sometimes the reverse. Several shifts in target type occurred during the task. RESULTS: Alcoholics made significantly more commission errors (i.e., press a key when a distracter displayed) and more omission errors (i.e., not press a key when a target displayed) than controls. Moreover, the number of commission errors was greater in alcoholics when alcohol-related stimuli had to be detected. CONCLUSIONS: These results demonstrate that alcoholics exhibit a basic prepotent response inhibition deficit, which is enhanced when the response to be suppressed is related to alcohol. We discuss clinical and theoretical implications of these findings.

Memory for angry faces, impulsivity, and problematic behavior in adolescence.

Research has shown that cognitive processes like the attribution of hostile intention or angry emotion to others contribute to the development and maintenance of conduct problems. However, the role of memory has been understudied in comparison with attribution biases. The aim of this study was thus to test if a memory bias for angry faces was related to conduct problems in youth. Adolescents from a junior secondary school were presented with angry and happy faces and were later asked to recognize the same faces with a neutral expression. They also completed an impulsivity questionnaire. A teacher assessed their behavior. The results showed that a better recognition of angry faces than happy faces predicted conduct problems and hyperactivity/inattention as reported by the teacher. The memory bias effect was more pronounced for impulsive adolescents. It is suggested that a memory bias for angry faces favors disruptive behavior but that a good ability to control impulses may moderate the negative impact of this bias.

How is impulsivity related to depression in adolescence? Evidence from a French validation of the cognitive emotion regulation questionnaire.

The aim of this study was to validate a French version of the Cognitive Emotion Regulation Questionnaire (CERQ; Garnefski, N., Kraaij, V., & Spinhoven, P., 2001. Negative life events, cognitive emotion regulation and emotional problems. Personality and Individual Differences, 30, 1311-1327) and to explore its relationships with impulsivity and depression. Teenagers from a junior secondary (n=107, 13-16 years) and a secondary school (n=110, 15-19 years) completed the CERQ, which assesses regulation strategies in response to negative events. The secondary school adolescents also completed the UPPS Impulsive Behavior Scale (Whiteside, S. P., & Lynam, D. R., 2001. The five factor model and impulsivity: Using a structural model of personality to understand impulsivity. Personality and Individual Differences, 30, 669-689) and the Reynolds Adolescent Depression Scale (Reynolds, W. M., 1987. Reynolds Adolescent Depression Scale: Professional manual. Odessa, FL: Psychological Assessment Resources). Factor analysis for the CERQ confirmed the presence of the nine original regulation strategies. In the secondary school students, impulsivity was related to depression. A path analysis revealed that regulation strategies mediated this relationship. The role of emotion regulation in the development of adolescent psychopathology is discussed.

Phenomenal characteristics of autobiographical memories for social and non-social events in social phobia.

Previous studies failed to show clear differences between people with social phobia and non-anxious individuals regarding the specificity and affective intensity of their autobiographical memories for social events. However, these studies did not assess the subjective experience associated with remembering. In this study, people with social phobia and non-anxious control participants recalled social and non-social events, and rated the phenomenal characteristics of their memories. The memories of people with social phobia for social events contained fewer sensorial details but more self-referential information than controls' memories. In addition, people with social phobia remembered social situations from an observer perspective, viewing themselves as if from outside, to a greater extent than controls. By contrast, the two groups did not differ concerning their memories for non-social events. These findings are discussed in relation to cognitive models of social phobia.

Impulsivity and decision making.

The purpose of the present study was to explore the links among the four facets of impulsivity (urgency, lack of premeditation, lack of perseverance, and sensation seeking) proposed by and decision-making processes. Thirty undergraduate students completed a self-report questionnaire evaluating impulsivity as well as a task measuring decision-making processes, the Iowa Gambling Task. Zero-order correlations and multilevel analysis revealed that only lack of premeditation was specifically linked to disadvantageous decisions on the Gambling Task. This suggests that premeditation is related to decision making influenced by somatic (or emotional) markers.

Cognitive biases toward alcohol-related words and executive deficits in polysubstance abusers with alcoholism.

AIM: To study cognitive biases for alcohol-related cues on executive function tasks involving mental flexibility and response inhibition in polysubstance abusers with alcoholism. DESIGN: The responses to alcohol-related cues of detoxified polysubstance abusers with alcoholism and of non-addicts were compared. SETTING: The University of Iowa City, Iowa, USA. PARTICIPANTS: Thirty detoxified polysubstance abusers with alcoholism (PSA) and 30 healthy non-substance abusers (CONT). MEASUREMENTS: Using the 'Alcohol Shifting Task', a variant of the go/no-go paradigm, we measured the response times and the accuracy of responses to targets and distracters. Sometimes the alcohol-related words were the targets for the 'go' response, with neutral words as distracters, sometimes the reverse. Several shifts in the type of the target occurred during the task. FINDINGS: Relative to CONT, PSA were generally slower to respond to targets, but the group difference was smaller when alcohol-related words were the targets. A signal detection analysis also indicated that relative to CONT, the PSA had more difficulties discriminating between targets and distracters (low d'), and they showed more signs of decision bias (low C), reflecting increased readiness to respond to both targets and distracters. However, these discrimination and inhibition deficits were more pronounced when alcohol-related words were the targets. Furthermore, the weaknesses in RT and C were more pronounced in PSA after shifting the targets from alcohol-related to neutral words, or vice versa. CONCLUSIONS: These results suggest that PSA have cognitive biases towards information related to alcohol, and that these biases, as well as the poor executive functions (lower mental flexibility and response inhibition) revealed in PSA might be responsible for their failure to maintain abstinence.