Effect of methamphetamine dependence on inhibitory deficits in a novel human open-field paradigm.

RationaleMethamphetamine (MA) is an addictive psychostimulant associated with neurocognitive impairment, including inhibitory deficits characterized by a reduced ability to control responses to stimuli. While various domains of inhibition such as exaggerated novelty seeking and perseveration have been assessed in rodents by quantifying activity in open-field tests, similar models have not been utilized in human substance abusers. We recently developed a cross-species translational human open-field paradigm, the human behavior pattern monitor (hBPM), consisting of an unfamiliar room containing novel and engaging objects. Previous work demonstrated that manic bipolar subjects exhibit a disinhibited pattern of behavior in the hBPM characterized by increased object interactions.ObjectivesIn the current study, we examined the effect of MA dependence on inhibitory deficits using this paradigm. hBPM activity and object interactions were quantified in 16 abstinent MA-dependent individuals and 18 matched drug-free comparison subjects. The Wisconsin card sorting task (WCST) and the positive and negative syndrome scale (PANSS) were administered to assess executive function and psychopathology.ResultsMA-dependent participants exhibited a significant increase in total object interactions, time spent with objects, and perseverative object interactions relative to comparison subjects. Greater object interaction was associated with impaired performance on the WCST, higher PANSS scores, and more frequent MA use in the past year.ConclusionsAbstinent MA-dependent individuals exhibited impaired inhibition in the hBPM, displaying increased interaction with novel stimuli. Utilization of this measure may enable assessment of inhibitory deficits relevant to drug-seeking behavior and facilitate development of intervention methods to reduce high-risk conduct in this population

Decreased modulation by the risk level on the brain activation during decision making in adolescents with internet gaming disorder

Greater impulse and risk-taking and reduced decision-making ability were reported as the main behavioral impairments in individuals with internet gaming disorder (IGD), which has become a serious mental health issue worldwide. However, it is not clear to date how the risk level modulates brain activity during the decision-making process in IGD individuals. In this study, 23 adolescents with IGD and 24 healthy controls (HCs) without IGD were recruited, and the balloon analog risk task (BART) was used in a functional magnetic resonance imaging experiment to evaluate the modulation of the risk level (the probability of balloon explosion) on brain activity during risky decision making in IGD adolescents. Reduced modulation of the risk level on the activation of the right dorsolateral prefrontal cortex (DLPFC) during the active BART was found in IGD group compared to the HCs. In the IGD group, there was a significant negative correlation between the risk-related DLPFC activation during the active BART and the Barratt impulsivity scale (BIS-11) scores, which were significantly higher in IGD group compared with the HCs. Our study demonstrated that, as a critical decision-making-related brain region, the right DLPFC is less sensitive to risk in IGD adolescents compared with the HCs, which may contribute to the higher impulsivity level in IGD adolescents

The Effect of Induction of Emotions on Risky Decisions and Behavioral Inhibition

In the present study, the effect of emotions on risky decision making and behavioral inhibition was investigated. The method of study was experimental. The research sample consisted of 60 male students with different educational degrees in Tehran University who were randomly assigned into two experimental groups and one control group (20 students in each group). In order to assess the risky decision-making and behavioral inhibition, two computerized tests, Balloon Analogue Risk Task (BART) and Go/No-Go Task were used. Positive and negative emotions were induced via an emotion induction procedure into two experimental groups. The results of multivariate analysis of variance (MANOVA) showed that different levels of independent variable including positive, negative and lack of emotion induction had a significant difference in both risky decision making and behavioral inhibition (p< 0.05). Generally, the results of the study showed that induction of positive emotions compared to negative emotions and the control group, significantly increases the risky decisions rate and reduces behavioral inhibitio

Strength of Response Suppression to Distracter Stimuli Determines Attentional-Filtering Performance in Primate Prefrontal Neurons

SummaryNeurons in the primate dorsolateral prefrontal cortex (dlPFC) filter attended targets distinctly from distracters through their response rates. The extent to which this ability correlates with the organism's performance, and the neural processes underlying it, remain unclear. We trained monkeys to attend to a visual target that differed in rank along a color-ordinal scale from that of a distracter. The animals' performance at focusing attention on the target and filtering out the distracter improved as ordinal distance between the stimuli increased. Importantly, dlPFC neurons also improved their filtering performance with increasing ordinal target-distracter distance; they built up their response rate in anticipation of the target-distracter onset, and then units encoding target representations increased their firing rate by similar amounts, whereas units encoding distracter representations gradually suppressed their rates as the interstimulus ordinal distance increased. These results suggest that attentional-filtering performance in primates relies upon dlPFC neurons' ability to suppress distracter representations

Les phénomènes de dépendance à l’environnement: réflexions sur l’autonomie humaine à partir de la clinique neurologique

Dans cet article, nous proposons d’analyser la perte d’autonomie caractérisée par les phénomènes de dépendance à l’environnement observés chez certains patients neurologiques présentant des lésions des lobes frontaux. Des propositions théoriques issues de la neuropsychologie cognitive et de la théorie de la médiation sont développées et confrontées. La démarche offre l’occasion, au plan théorique, de questionner la détérioration possible du système de la personne suite à des lésions cérébrales et, au plan méthodologique, d’interroger notre manière d’examiner ces patients en confrontant les modèles théoriques aux observations clinique

Effects of Marijuana on Risky Decision-Making in Young Adult College Students

Marijuana (MJ) is a widely used illicit substance among adolescents and young adults. Frequent MJ use has been associated with impairments in cognitive flexibility and inhibition, both of which play important roles in decision-making. However, the impact of frequent MJ on decision-making performance is mixed and not well understood. The current study examined the influence of heavy MJ use on risky decision-making in college students, 18-22 years old. Participants completed the Iowa Gambling Task (IGT), a measure of risky decision-making, and net IGT scores (advantageous-disadvantageous decisions) were used as a measure of optimal decision-making. A trend was found for the effect of group on net IGT scores, such that marijuana users (MJ+) had lower net IGT scores than healthy controls (HC). The final model with main effects of group and sex showed a significant effect of group on net IGT scores and a trend for the main effect of sex. MJ+ had lower net IGT scores than HC and female participants had a trend towards lower net IGT scores than male participants. These findings highlight potential differences in risky decision-making between young adult MJ users and healthy controls, but it is uncertain whether these differences are pre-existing and increase vulnerability for heavy MJ use or if they are related to the effects of heavy MJ use

The computational neurology of movement under active inference

We propose a computational neurology of movement based on the convergence of theoretical neurobiology and clinical neurology. A significant development in the former is the idea that we can frame brain function as a process of (active) inference, in which the nervous system makes predictions about its sensory data. These predictions depend upon an implicit predictive (generative) model used by the brain. This means neural dynamics can be framed as generating actions to ensure sensations are consistent with these predictions-and adjusting predictions when they are not. We illustrate the significance of this formulation for clinical neurology through simulating a clinical examination of the motor system; i.e. an upper limb coordination task. Specifically, we show how tendon reflexes emerge naturally under the right kind of generative model. Through simulated perturbations, pertaining to prior probabilities of this model's variables, we illustrate the emergence of hyperreflexia and pendular reflexes, reminiscent of neurological lesions in the corticospinal tract and cerebellum. We then turn to the computational lesions causing hypokinesia and deficits of coordination. This in silico lesion-deficit analysis provides an opportunity to revisit classic neurological dichotomies (e.g. pyramidal versus extrapyramidal systems) from the perspective of modern approaches to theoretical neurobiology-and our understanding of the neurocomputational architecture of movement control based on first principles