Lateral prefrontal model-based signatures are reduced in healthy individuals with high trait impulsivity

High impulsivity is an important risk factor for addiction with evidence from endophenotype studies. In addiction, behavioral control is shifted toward the habitual end. Habitual control can be described by retrospective updating of reward expectations in ‘model-free’ temporal-difference algorithms. Goal- directed control relies on the prospective consideration of actions and their outcomes, which can be captured by forward-planning ‘model-based’ algorithms. So far, no studies have examined behavioral and neural signatures of model- free and model-based control in healthy high-impulsive individuals. Fifty healthy participants were drawn from the upper and lower ends of 452 individuals, completing the Barratt Impulsiveness Scale. All participants performed a sequential decision-making task during functional magnetic resonance imaging (fMRI) and underwent structural MRI. Behavioral and fMRI data were analyzed by means of computational algorithms reflecting model-free and model-based control. Both groups did not differ regarding the balance of model-free and model-based control, but high-impulsive individuals showed a subtle but significant accentuation of model-free control alone. Right lateral prefrontal model-based signatures were reduced in high-impulsive individuals. Effects of smoking, drinking, general cognition or gray matter density did not account for the findings. Irrespectively of impulsivity, gray matter density in the left dorsolateral prefrontal cortex was positively associated with model-based control. The present study supports the idea that high levels of impulsivity are accompanied by behavioral and neural signatures in favor of model-free behavioral control. Behavioral results in healthy high-impulsive individuals were qualitatively different to findings in patients with the same task. The predictive relevance of these results remains an important target for future longitudinal studies

The Neural Basis of Decision-Making and Reward Processing in Adults with Euthymic Bipolar Disorder or Attention-Deficit/Hyperactivity Disorder (ADHD)

Attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BD) share DSM-IV criteria in adults and cause problems in decision-making. Nevertheless, no previous report has assessed a decision-making task that includes the examination of the neural correlates of reward and gambling in adults with ADHD and those with BD

Het nemen van beslissingen door volwassenen met ADHD:Een systematisch literatuuronderzoek

Personen met aandachtstekortstoornis met hyperactiviteit (ADHD) hebben een grotere kans om minder goede (levens)beslissingen te nemen en om risicovolle activiteiten te ondernemen dan personen zonder ADHD. Mogelijk komt dit doordat de kenmerken van ADHD van invloed zijn op het besluitvormingsproces. Hoewel beslissingsproblematiek reeds uitgebreid is onderzocht bij kinderen en adolescenten met ADHD, is er nog relatief weinig bekend over de besluitvorming van volwassenen met ADHD. Om die reden was het doel van dit literatuuronderzoek de aard en omvang van eventuele tekorten in het besluitvormingsproces van volwassenen met ADHD vast te stellen. Hiertoe is de bestaande literatuur, waarin de prestatie van volwassenen met ADHD op beslissingstaken werd vergeleken met de prestatie van een gezonde controlegroep, systematisch doorzocht, waartoe de databases PsycINFO, MEDLINE en PubMed zijn geraadpleegd. In totaal werden er 31 studies geïncludeerd. In de meerderheid van de studies (i.e. 55 %) weken de prestaties van volwassenen met ADHD af op een of meer van de gebruikte beslissingstaken in vergelijking met de controlegroep(en). Dit literatuuronderzoek levert daarmee voorzichtig bewijs voor het bestaan van verschillen in het besluitvormingsproces tussen gezonde individuen en volwassenen met ADHD. De grote inconsistentie in de bevindingen wordt deels verklaard door de verscheidenheid aan domeinen van besluitvorming die werden onderzocht, de comorbide stoornissen van de participanten en het medicatiegebruik in de ADHD-groepen. Het literatuuronderzoek besluit met een bespreking van de implicaties die de bevindingen hebben voor theorieën over de onderliggende mechanismen van ADHD

Risk factors for addiction and their association with model-based behavioral control

Addiction shows familial aggregation and previous endophenotype research suggests that healthy relatives of addicted individuals share altered behavioral and cognitive characteristics with individuals suffering from addiction. In this study we asked whether impairments in behavioral control proposed for addiction, namely a shift from goal-directed, model-based toward habitual, model-free control, extends toward an unaffected sample (n = 20) of adult children of alcohol-dependent fathers as compared to a sample without any personal or family history of alcohol addiction (n = 17). Using a sequential decision-making task designed to investigate model-free and model-based control combined with a computational modeling analysis, we did not find any evidence for altered behavioral control in individuals with a positive family history of alcohol addiction. Independent of family history of alcohol dependence, we however observed that the interaction of two different risk factors of addiction, namely impulsivity and cognitive capacities, predicts the balance of model-free and model-based behavioral control. Post-hoc tests showed a positive association of model-based behavior with cognitive capacity in the lower, but not in the higher impulsive group of the original sample. In an independent sample of particularly high- vs. low-impulsive individuals, we confirmed the interaction effect of cognitive capacities and high vs. low impulsivity on model-based control. In the confirmation sample, a positive association of omega with cognitive capacity was observed in highly impulsive individuals, but not in low impulsive individuals. Due to the moderate sample size of the study, further investigation of the association of risk factors for addiction with model-based behavior in larger sample sizes is warranted

Wie viel Information brauchen wir? Selbstlokalisation und Wege finden mit schematisierten Karten

Welche Information ist notwendig um sich zu orientieren? In zwei Feldexperimenten wurde ein Grundriss mit drei stark schematisierten Karten verglichen, die nur Routenwissen bereitstellten. Mit Hilfe der Karte bestimmten die 32 Probanden in je zwei Aufgaben ihre Position in einem ihnen unbekannten komplexen mehrstöckigen Gebäude und mussten verschiedene Ziele finden. Kartennutzung und verschiedene Leistungsmaße wurden erhoben. Trotz der spärlicheren Information fanden die Probanden ihr Ziel mit der eindeutigen Schemakarte besser, als mit dem Grundriss. Keine Unterschiede ergaben sich in der Selbstlokalisation. Beide Gruppen orientierten sich vermutlich an der Netzwerkstruktur der Wege und nicht an lokaler Geometrie, was den Suchraum möglicher Standpunkte verkleinert. Die Nutzung der schematisierten Karte erfolgte schneller. Hoch schematisierte Karten mit weniger als der Standardinformation können zu besserer Leistung führen. Die Ergebnisse werden im Kontext von Routen und Überblickswissen interpretiert

CMOS-compatible field effect nanoscale gas-sensor: Operation and annealing models

Complete modelling of electrically controlled nanoscale gas sensors with Poisson, Wolkenstein, Fokker-Planck and continuity is presented. Based on a plausible Drift explanation we developed suitable models for sensitivity control and operational modes. An onset for CMOS-complying annealing procedures is given