Biomedical subjects

Eldad Yechiam

Publications and source records attributed to Eldad Yechiam.

10 recordsLinked to original sources

PubMed2006

Emotion-based decision-making in healthy subjects: short-term effects of reducing dopamine levels.

INTRODUCTION: Converging evidences from animal and human studies suggest that addiction is associated with dopaminergic dysfunction in brain reward circuits. So far, it is unclear what aspects of addictive behaviors are related to a dopaminergic dysfunction. DISCUSSION: We hypothesize that a decrease in dopaminergic activity impairs emotion-based decision-making. To demonstrate this hypothesis, we investigated the effects of a decrease in dopaminergic activity on the performance of an emotion-based decision-making task, the Iowa gambling task (IGT), in 11 healthy human subjects. MATERIALS AND METHODS: We used a double-blind, placebo-controlled, within-subject design to examine the effect of a mixture containing the branched-chain amino acids (BCAA) valine, isoleucine and leucine on prolactin, IGT performance, perceptual competency and visual aspects of visuospatial working memory, visual attention and working memory, and verbal memory. The expectancy-valence model was used to determine the relative contributions of distinct IGT components (attention to past outcomes, relative weight of wins and losses, and choice strategies) in the decision-making process. OBSERVATIONS AND RESULTS: Compared to placebo, the BCAA mixture increased prolactin levels and impaired IGT performance. BCAA administration interfered with a particular component process of decision-making related to attention to more recent events as compared to more distant events. There were no differences between placebo and BCAA conditions for other aspects of cognition. Our results suggest a direct link between a reduced dopaminergic activity and poor emotion-based decision-making characterized by shortsightedness, and thus difficulties resisting short-term reward, despite long-term negative consequences. These findings have implications for behavioral and pharmacological interventions targeting impaired emotion-based decision-making in addictive disorders.

Amino Acids, Branched-Chain↗

PubMed2006

Decision-making impairments in adolescents with early-onset schizophrenia.

Adolescence is a time of vulnerability for risk-taking behaviors. This is particularly true of adolescents with schizophrenia who present with high rates of substance use as compared to the general population. Using the Iowa Gambling Task (IGT), the authors compared decision-making processes in adolescents with early-onset schizophrenia (onset of psychosis by age 18) to that of healthy volunteers. Fifteen adolescents with schizophrenia (aged 12-21 years) and 25 demographically similar healthy volunteers were administered the IGT. Overall, adolescents with schizophrenia performed significantly worse on the IGT than healthy adolescents as measured by a significant group by block interaction. Post-hoc testing revealed that adolescents with schizophrenia performed more poorly than healthy adolescents during the last two blocks of the task. Mathematical modeling further indicated that adolescents with schizophrenia allocated significantly more attention to monetary gains than losses encountered during the task, suggesting a hypersensitivity to rewards and relative insensitivity to future consequences. This is similar to what has been reported for adults with externalizing forms of psychopathology, such as those who abuse substances. These findings have potential implications for understanding the increased vulnerability for the development of substance abuse in adolescents with schizophrenia.

Adolescent↗

PubMed2006

Motivational processes and autonomic responsivity in Asperger's disorder: evidence from the Iowa Gambling Task.

Asperger's disorder (ASP), like other autism spectrum disorders, is associated with altered responsiveness to social stimuli. This study investigated learning and responsiveness to nonsocial, but motivational, stimuli in ASP. We examined choice behavior and galvanic skin conductance responses (SCRs) during the Iowa Gambling Task (IGT; Bechara et al., 1994) in 15 adolescents and young adults with ASP and 14 comparison subjects. We examined aspects of learning, attention to wins and losses, and response style with a formal cognitive model, the Expectancy-Valence Learning model (Busemeyer & Stout, 2002). The ASP group did not differ from the comparison group in proportions of selections from advantageous decks. However, ASP participants showed a distinct pattern of selection characterized by frequent shifts between the four IGT decks, whereas comparison participants developed clear deck preferences. SCR results showed some evidence of reduced responsiveness in the ASP group during the IGT. Results from the cognitive model indicated that, in contrast to the comparison group, the ASP group's selections were less consistent with the motivational significance they assigned to decks. Findings are discussed in the context of the neurobiological substrates associated with IGT performance.

Adolescent↗

PubMed2006

A formal cognitive model of the go/no-go discrimination task: evaluation and implications.

This article proposes and tests a formal cognitive model for the go/no-go discrimination task. In this task, the performer chooses whether to respond to stimuli and receives rewards for responding to certain stimuli and punishments for responding to others. Three cognitive models were evaluated on the basis of data from a longitudinal study involving 400 adolescents. The results show that a cue-dependent model presupposing that participants can differentiate between cues was the most accurate and parsimonious. This model has 3 parameters denoting the relative impact of rewards and punishments on evaluations, the rate that contingent payoffs are learned, and the consistency between learning and responding. Commission errors were associated with increased attention to rewards; omission errors were associated with increased attention to punishments. Both error types were associated with low choice consistency. The parameters were also shown to have external validity: Attention to rewards was associated with externalizing behavior problems on the Achenbach scale, and choice consistency was associated with low Welsh anxiety. The present model can thus potentially improve the sensitivity of the task to differences between clinical populations.

Adolescent↗

PubMed2006

Application of a computational decision model to examine acute drug effects on human risk taking.

In 3 previous experiments, high doses of alcohol, marijuana, and alprazolam acutely increased risky decision making by adult humans in a 2-choice (risky vs. nonrisky) laboratory task. In this study, a computational modeling analysis known as the expectancy valence model (J. R. Busemeyer & J. C. Stout, 2002) was applied to individual-participant data from these studies, for the highest administered dose of all 3 drugs and corresponding placebo doses, to determine changes in decision-making processes that may be uniquely engendered by each drug. The model includes 3 parameters: responsiveness to rewards and losses (valence or motivation); the rate of updating expectancies about the value of risky alternatives (learning/memory); and the consistency with which trial-by-trial choices match expected outcomes (sensitivity). Parameter estimates revealed 3 key outcomes: Alcohol increased responsiveness to risky rewards and decreased responsiveness to risky losses (motivation) but did not alter expectancy updating (learning/memory); both marijuana and alprazolam produced increases in risk taking that were related to learning/memory but not motivation; and alcohol and marijuana (but not alprazolam) produced more random response patterns that were less consistently related to expected outcomes on the 2 choices. No significant main effects of gender or dose by gender interactions were obtained, but 2 dose by gender interactions approached significance. These outcomes underscore the utility of using a computational modeling approach to deconstruct decision-making processes and thus better understand drug effects on risky decision making in humans.

Alcohol Drinking↗

PubMed2006

Working memory and decision-making biases in young adults with a family history of alcoholism: studies from the Oklahoma family health patterns project.

BACKGROUND: Alcohol misuse is more common in persons with a family history of alcoholism (FH+) than in those with no such history (FH-). Among FH+, behavioral disinhibition and male sex seem to signal the presence of an increased risk. METHODS: This study examined cognitive and behavioral characteristics of 175 nonabusing 18- to 30-year-olds, 87 FH+ and 88 FH-, who were further characterized by their degree of behavioral disinhibition using the Sociability scale of the California Personality Inventory. Working memory and decision making were tested using the Stroop Color-Word Test and the Iowa Gambling Task, a simulated card game. RESULTS: Persons with a family history of alcoholism who were behaviorally disinhibited displayed significantly greater interference on the Stroop task than the other subgroups. On the Iowa Gambling Task, FH+ males, but not the females, were significantly more attentive to financial gains than other subgroups, and they had greater consistency in their choice behaviors. CONCLUSIONS: Persons with a family history of alcoholism, in combination with behavioral disinhibition, appears to signal working memory deficits and in combination with male sex indicates an attraction to the rewarding aspects of a risk-taking challenge. These findings are not secondary to heavy exposure to alcohol or other drugs, but instead reflect intrinsic risk-related familial and personal characteristics of the subjects.

Adolescent↗

PubMed2005

Using cognitive models to map relations between neuropsychological disorders and human decision-making deficits.

Findings from a complex decision-making task (the Iowa gambling task) show that individuals with neuropsychological disorders are characterized by decision-making deficits that lead to maladaptive risk-taking behavior. This article describes a cognitive model that distills performance in this task into three different underlying psychological components: the relative impact of rewards and punishments on evaluations of options, the rate that the contingent payoffs are learned, and the consistency between learning and responding. Findings from 10 studies are organized by distilling the observed decision deficits into the three basic components and locating the neuropsychological disorders in this component space. The results reveal a cluster of populations characterized by making risky choices despite high attention to losses, perhaps because of difficulties in creating emotive representations. These findings demonstrate the potential contribution of cognitive models in building bridges between neuroscience and behavior.

Cognition Disorders↗

PubMed2005

Comparison of basic assumptions embedded in learning models for experience-based decision making.

The present study examined basic assumptions embedded in learning models for predicting behavior in decisions based on experience. In such decisions, the probabilities and payoffs are initially unknown and are learned from repeated choice with payoff feedback. We examined combinations of two rules for updating past experience with new payoff feedback and of two choice rule assumptions for mapping experience onto choices. The combination of these assumptions produced four classes of models that were systematically compared. Two methods were employed to evaluate the success of learning models for approximating players' choices: One was based on estimating parameters from each person's data to maximize the prediction of choices one step ahead, conditioned by the observed past history of feedback. The second was based on making a priori predictions for the entire sequence of choices using parameters estimated from a separate experiment. The results indicated the advantage of a class of models incorporating decay of previous experience, whereas the ranking of choice rules depended on the evaluation method used.

Adult↗

PubMed2004

Easy first steps and their implication to the use of a mouse-based and a script-based strategy.

The present study evaluated the convention to design training environments by giving access to easy strategies first and progressing to more difficult and efficient strategies thereafter. An experiment was conducted focusing on training in a simplified editing task. This task could be performed with an easy (mouse-based) strategy as well as with a more efficient (script-based) strategy. Two learning environments were compared, based on the order of the introduction of the following 2 strategies to participants: an easy-first program and a difficult-first program. The results highlight 2 interesting patterns. First, initial training in an easy strategy impaired the acquisition of a more efficient strategy. Second, learning the easy strategy first reduced between-subjects variability. It helped poor performers but resulted in a lower proportion of high-level performers.

Choice Behavior↗

PubMedDate not supplied

Melioration and the transition from touch-typing training to everyday use.

Previous research shows that success in touch-typing training does not ensure its continuation into everyday use. It is postulated that an important contributor to this problem is melioration--that is, maximizing local rates of reinforcement. In the context of typing, melioration implies an intuitive tendency to choose typing strategies that lead to a better immediate performance level than that obtained by touchtyping. One such strategy is visually guided typing, in which the performer looks at the keys to locate their position. The present research describes a training approach that changes the reinforcement structure by increasing the attractiveness of looking at the screen while typing. This approach is implemented by using a secondary task that requires typists to respond to signals appearing on the screen. In an experiment that evaluated this solution, 22 students were given a touch-typing training course followed by a period in which they had to type their own homework. The results showed that under a modified reinforcement condition, the effect of melioration on touch-typing scores in the posttraining phase decreased. In addition, the experimental manipulation facilitated the acquisition and maintenance of the touch-typing skill. Actual or potential applications of this research include research in training, choice behavior, and human-computer interaction.

Adult↗