Der Persönlichkeitsfaktor Impulsivität und eine verminderte Inhibitionsfähigkeit werden als Risikofaktoren für Suchterkrankungen diskutiert. Impulsivität ist ein multidimensionales Konstrukt und lässt sich durch Fragebögen wie die Barratt Impulsiveness Scale (BIS-11) quantifizieren. Inhibitionsfähigkeit kann mit Hilfe eines Stop-Signal Task operationalisiert werden und wird von einigen Autoren als Subdomäne von Impulsivität angesehen (Response Inhibition). Welche Domänen des Persönlichkeitsmerkmals Impulsivität die behavioralen und neuronalen Korrelate von Inhibitionsfähigkeit abbilden, ist allerdings bis jetzt nicht eindeutig geklärt. Auch Veränderungen der Belohnungswahrnehmung tragen zur Pathogenese von Suchterkrankungen bei, und belohnungsassoziierte Aktivierungen im ventralen Striatum weisen bei Gesunden eine positive Beziehung zu Impulsivität auf. Die impulsivitätsabhängigen Auswirkungen von Belohnungsverarbeitung auf die Inhibitionsfähigkeit sind jedoch unzureichend verstanden. Zur weiteren Untersuchung der Beziehung von Impulsivität und Inhibitionsfähigkeit sowie ihrer Interaktion mit Belohnungsverarbeitung selektierten wir aus einer Gruppe von 452 Probanden je 26 hoch und niedrig impulsive Probanden, deren durchschnittliche BIS-11 Werte den Kriterien für hohe bzw. niedrige Impulsivität entsprachen. Alle 52 Probanden absolvierten einen Stop-Signal Task mit integrierter Belohnungskomponente während einer simultanen funktionellen MRT Messung (fMRT). Neben einer neuropsychologischen Testung erhielten die Probanden eine umfassende Charakterisierung ihrer Persönlichkeits- und Impulsivitätsdomänen durch die Fragebögen UPPS (Urgency, Lack of Premeditation, Lack of Perseverance, Sensation Seeking), Sensation Seeking Scale und NEO-Fünf-Faktoren-Inventar. Die Auswertung der Verhaltensdaten erfolgte mit SPSS, die Analyse der fMRT-Daten nach einer Vorverarbeitung mit SPM getreu des General Linear Model. Für die Extremgruppen des BIS-11 fanden wir, entgegen unserer anfänglichen Vermutung, keinen signifikanten Gruppenunterschied, weder hinsichtlich der behavioral gemessenen Inhibitionsfähigkeit (SSRT), noch im neuronalen Aktivierungsmuster des Inhibitionsnetzwerks. Eine feinere Untersuchung unter Einbezug der Impulsivitätsubdomänen zeigte, dass die Subdimension Urgency die individuelle Inhibitionsfähigkeit der Probanden am besten vorhersagte und eine positive Korrelation mit dem Inhibitionsmaß SSRT aufwies. Interessanterweise zeigten Urgency-Werte zusätzlich auch eine negative Korrelation mit den neuronalen Aktivierungen im rechten inferior-frontalen Gyrus, einer Schlüsselregion des Inhibitionsnetzwerks. Belohnte erfolgreiche Stop-Trials wiesen gegenüber nicht erfolgreichen belohnten Stop-Trials auf neuronaler Ebene eine verstärkte Aktivierung des ventralen Striatums auf. Diese Aktivierung zeigte Ähnlichkeit mit einem Prädiktionsfehlersignal und könnte möglicherweise ein selbst generiertes Feedbacksignal darstellen. Nur Probanden mit niedrigen Urgency-Werten konnten dieses potentielle Feedbacksignal für eine verbesserte Inhibition (kürzere SSRT) nutzen, während sich dieser Zusammenhang nicht für Probanden mit höheren Urgency-Werten zeigte. Die Ergebnisse verdeutlichen, dass die Beziehung zwischen Impulsivität und behavioraler Inhibitionsfähigkeit vorsichtig und gezielt multidimensional betrachtet werden sollte. Während der Gesamtscore des BIS-11 Response Inhibition nicht ausreichend abzubilden scheint, zeigte die Subdimension Urgency sowohl behavioral als auch neuronal eine Assoziation mit einer verminderten Inhibitionsfähigkeit. Interessanterweise weist Urgency auch eine Verbindung zur Belohnungsverarbeitung im Stop-Signal Task auf und scheint mit dem Nutzen von potentiellen individuellen Feedbacksignalen verknüpft zu sein. Da Urgency-Werte sich bei verschiedenen psychischen Störungen, wie Abhängigkeitserkrankungen, erhöht zeigen, stellt Urgency möglicherweise ein Bindeglied zwischen Response Inhibition und Belohnungsverarbeitung dar. Aus diesen Gründen sollte Urgency in zukünftigen Studien zu den Entstehungsmechanismen von Suchterkrankungen als Moderator von behavioraler Handlungsadaption miteinbezogen werden.

The experiments reported in this thesis were conducted to examine the effects of executive-control and associative-learning processes on performance in conventional executive-control paradigms. For this purpose, I developed comparative task-switching and response-inhibition paradigms, which were used to assess the performance of pigeons, whose behaviour is presumably based purely on associative processes, and of humans, whose behaviour may be guided by executive control and by associative processes. Pigeons were able to perform accurately in the comparative paradigms; hence, associative-learning processes are sufficient to account for successful performance. However, some task-specific effects that can be attributed to executive-control processes, and which were found in humans applying executive control, were absent or greatly reduced in pigeons. Those effects either reflect the mental operations that are performed to ensure that a specific set of stimulus-response-contingencies is applied and any contingencies belonging to a different set are suppressed, or reflect mental preparations for the possibility that the requirement to execute a certain response suddenly changes. In particular, in Chapter 3, it is shown that the benefits of repeatedly applying the same set of stimulus-response contingencies (or, in reverse, the costs of switching from one set to another) do not apply when Pavlovian processes dominate learning, which is likely the case for pigeons. Furthermore, as shown in Chapters 4 and 5, the behavioural effects of preparing for an unpredicted change in response requirements appeared to be absent when behaviour was based purely on associative processes. Instead, associatively mediated performance was primarily influenced by the stimulus-response contingencies that were effective in each paradigm. Repeating the same response in consecutive trials facilitated the performance of pigeons and associatively learning human participants in the task-switching paradigms, and performing a particular Go response increased the pigeons' likelihood of executing that response in the following trial in two response-inhibition paradigms. In summary, any behavioural effects that can be observed at the level of abstract task requirements reflect the influence of executive-control processes, both in task-switching paradigms and in response-inhibition paradigms.

The smartphone has quickly become the most used device to access the internet. Academic and public concern has been raised if overuse of smartphone technology can have detrimental effects on brain and behavior. Preliminary results suggest that excessive smartphone usage may be linked to impaired inhibitory control. The present study investigates whether such a relationship is present in a sample of healthy individuals with varying degrees of usage. To investigate the proposed relationship, the Stroop color and word task and the stop-signal task was utilized to measure inhibitory control, while screen time was utilized to measure duration of smartphone usage. A Pearson‘s correlation analysis and an independent t-test/Mann Whitney-U test analyzed the results, which did not yield statistical significance.

Bisherige Untersuchungen deuten darauf hin, dass ein höherer BMI mit einer reduzierten inhibitorischen Kontrolle verbunden sei. Allerdings sind die bisherigen Ergebnisse zum Teil widersprüchlich und die Untersuchungen erfolgten hauptsächlich bei weiblichen Versuchspersonen. Ich untersuchte gezielt die inhibitorische Kontrolle innerhalb und außerhalb des Essenskontextes bei Männern und Frauen unterschiedlichen Gewichtes. Außerdem erfolgte eine Bewertung von unterschiedlichen Essensbildern nach deren Schmackhaftigkeit und die Erhebung von Verhaltensmerkmalen zum Essverhalten und der Impulsivität mittels Fragebögen. Ich konnte zeigen, dass Frauen niedrigkalorische Nahrungsmittel schmackhafter bewerteten als Männer. Außerdem hatten Frauen eine bessere inhibitorische Kontrolle nach der Ansicht von hochkalorischen Nahrungsmittel im Vergleich zu niedrigkalorischen Nahrungsmitteln. Es gab einen statistischen Trend für eine bessere inhibitorische Kontrolle nach der Ansicht von hochkalorischen Nahrungsmitteln bei Frauen gegenüber Männern. Es konnte kein direkter Zusammenhang zwischen Gewicht und inhibitorischer Kontrolle sowohl innerhalb als auch außerhalb des Essenskontextes gefunden werden. Allerdings konnte ich zeigen, dass es einen Moderationseffekt der Merkmalsimpulsivität auf den Zusammenhang zwischen inhibitorischer Kontrolle und BMI für den hochkalorischen Essenskontext gab. Dies deutet auf einen komplexen Zusammenhang zwischen Merkmalsimpulsivität, BMI und inhibitorischer Kontrolle hin. Mit meinen Ergebnissen konnte ich zeigen, dass adipöse Personen nicht an einer verminderten inhibitorischen Kontrolle per se leiden. Die Unterdrückung einer unerwünschten Handlung scheint vielmehr von sozialen Normen und dem aktuellen Kontext abzuhängen. Zusätzlich interagieren Faktoren wie Geschlecht und Merkmalsimpulsivität mit der inhibitorischen Kontrolle. / Recent research indicates that reduced inhibitory control is associated with higher body mass index (BMI), higher food craving and increased food intake. However, experimental evidence for the relationship between response inhibition and weight status is inconsistent and to date has been investigated predominantly in women. In the current study, 56 participants (26 obese, 30 lean; 27 female, 29 male)performed a Food Picture Rating Task followed by a Stop Signal Task where pictures of palatable high or low caloric food or non-food items were presented prior to the Go signal. We further assessed participants’ self-reported eating behavior and trait impulsivity as potential factors influencing response inhibition, in particular within the food context. Independent of BMI, women showed significantly higher liking for low caloric food items than men. This was accompanied by shorter Stop Signal Reaction Times (SSRT) after high compared to low caloric food pictures for women, and shorter SSRT in women compared to men for high caloric food. No influence of gender on SSRT was observable outside of the food context. While SSRTs did not differ between obese and lean participants across the three Picture categories, we found a moderating effect of trait impulsivity on the relationship between BMI and SSRT, specifically in the high caloric food context. Higher BMI was predictive of longer SSRT only for participants with low to normal trait impulsivity, pointing at a complex interplay between response inhibition, general impulsivity and weight status. Our results support the notion that individuals with obesity do not suffer from diminished response inhibition capacity per se. Rather, the ability to withhold a Response depends on context and social norms, and strongly interacts with factors like gender and trait impulsivity.

Objective: The strong association between ADHD and cigarette smoking and the known effects of nicotine on cognition has lead to interest in the role of cholinergic function in ADHD cognitive deficits. We have previously demonstrated that acute nicotine improves behavioral inhibition in adolescents with ADHD. This study examined acute nicotine in young adults with ADHD-Combined type on cognitive domains including behavioral inhibition, delay aversion, and recognition memory. Methods: 15 non-smoking young adults (20 ± 1.7 years) diagnosed with ADHD-C received acute nicotine (7 mg patch for 45 min) and placebo on separate days. Cognitive tasks included the Stop Signal Task, Choice Delay task, and the High-Low Imagery Task (a verbal recognition memory task). Three subjects experienced side effects and their data was excluded from analysis of cognitive measures. Results: There was a significant (p < .05) positive effect of nicotine on the Stop Signal Reaction Time measure of the Stop Signal Task. The SSRT was improved without changes in GO reaction time or accuracy. There was a trend (p = .09) for nicotine to increase tolerance for delay and a strong trend (p = .06) for nicotine to improve recognition memory. Conclusions: Non-smoking young adults with ADHD-C showed improvements in cognitive performance following nicotine administration in several domains that are central to ADHD. The results from this study support the hypothesis that cholinergic system activity may be important in the cognitive deficits of ADHD and may be a useful therapeutic target.

No description available.

Background: Individuals with binge eating disorder (BED) experience a loss of control (i.e., poor inhibitory control) during binge eating, where stress is a common antecedent for binge episodes. However, few studies examine acute stress in BED and, to date, psychosocial stress relationships with inhibitory control are unexamined. Purpose: The current study investigated acute psychosocial stress effects on inhibitory control in BED. Additionally, inhibitory control relationships with BED treatment outcome were explored. Methods: Thirty-three individuals with BED were randomized to a stress (n = 17) or no stress condition (n = 16). All completed self-report measures including the Profile of Mood States and the Binge Urge Scale. Following the stressor, individuals completed the Stop-Signal Task (SST), a well-validated measure of inhibitory control. Relationships between post-stress anxiety with inhibitory control and eating pathology were explored. Furthermore, treatment outcome relationships with levels of inhibitory control, and negative urgency (an impulsive personality trait) were explored. Results: In the stress condition, individuals reported increased state anxiety immediately following stress, but experienced a decrease back to baseline levels of anxiety by the end of the SST. Stress resulted in impaired inhibitory control performance on the SST. Binge urges increased across both conditions over time. Measures of inhibitory control and negative urgency did not relate to treatment outcome. Conclusion: This study is novel in directly examining psychosocial stress effects on inhibitory control, which has not been studied in BED. These results show subjective stress effects in BED are short-lived; however, behaviourally, stress has a lingering effect on inhibitory control. Increasing binge urges across the experimental session in the no stress condition suggests a role for generalized anxiety on this impulse. These findings have clinical implications for binge urges as a therapeutic target, and for informing individuals with BED about the implications of stress on their binge eating. / Thesis / Master of Science (MSc)

No description available.

Malgré de nombreux efforts de prévention, les jeunes conducteurs sont surreprésentés dans les accidents routiers. Certaines études ont visé à mettre en évidence les facteurs pouvant influencer les jeunes conducteurs à adopter des comportements risqués. La consommation de cannabis et l’impulsivité ont été identifiées comme des facteurs importants. L’objectif de cette thèse vise à mieux comprendre les liens entre la consommation de cannabis et les comportements routiers risqués, tout en tenant compte de l’impulsivité. Pour ce faire, cette thèse se divise en deux articles. Le premier article vise à vérifier si la fréquence de consommation de cannabis prédit la prise de risque des jeunes conducteurs au-delà de l’effet de leur impulsivité. 209 participants âgés de 17 à 25 ans ont rempli des questionnaires sur leurs comportements routiers, leur impulsivité, et leur fréquence de consommation de cannabis. Les résultats montrent que la fréquence de consommation de cannabis prédit la prise de risque des jeunes conducteurs au-delà de l’effet de l’impulsivité. De plus, l’urgence positive est la seule facette de l’impulsivité qui prédit la prise de risque, indépendamment des habitudes de consommation. Plusieurs hypothèses pouvant expliquer ces résultats ont été proposées dont une qui nous semblait particulièrement pertinente : la probabilité de prendre le volant après avoir consommé est plus élevée dans le cas d’une consommation plus fréquente, ainsi l’effet direct de la substance pourrait expliquer les comportements risqués. C’est pourquoi dans notre deuxième étude, nous avons voulu vérifier si la consommation de cannabis était associée aux comportements risqués même lorsque le consommateur n’est pas sous l’effet du cannabis. Comme une consommation fréquente peut être symptomatique d’un trouble d’utilisation du cannabis (TUC), nous avons voulu vérifier son impact sur les comportements risqués. Le deuxième article compare donc un groupe de consommateurs ayant un TUC avec un groupe n’en ayant pas sur des comportements risqués tout en tenant compte de leur impulsivité. Pour ce faire, 76 participants masculins, consommateurs de cannabis, âgés de 18 à 25 ans, ont complété une tâche de simulation de conduite ainsi qu’une tâche stop-signal, s’étant abstenus de 6 consommer du cannabis dans les 12 heures précédant l’expérimentation. Ils ont aussi rempli des questionnaires sur les habitudes de consommation de cannabis, les traits d’impulsivité et la prise de risque. Les consommateurs ayant un TUC ont manifesté plus de comportements risqués dans le simulateur que ceux n’en ayant pas, quel que soit leur niveau d’impulsivité et sans être sous l’effet de la substance. Plusieurs explications ont été proposées : difficulté d’adaptation à la conduite sans l’effet de la substance; présence d’une autre variable confondante que l’impulsivité sous-jacente à la consommation et aux comportements risqués; effet résiduel de la substance, non détecté par la tâche stop-signal, qui influencerait les comportements routiers. En résumé, il ressort de cette thèse que la consommation de cannabis est un facteur contribuant aux comportements risqués des jeunes conducteurs, et ce indépendamment de l’impulsivité. De plus, les consommateurs ne constituent pas un groupe homogène, d’où la pertinence de cibler particulièrement les consommateurs problématiques dans les campagnes de prévention. / Despite many prevention efforts, young drivers are overrepresented in road crashes. Some studies show that cannabis use and impulsivity are significant predictors of risky driving behaviour among young drivers. The aim of this thesis is to better understand the association between cannabis use and risky driving behaviour, while considering the driver’s impulsivity. For this purpose, this thesis is divided into two articles. The first article aims to verify whether the frequency of cannabis use predicts risk-taking over and above the impulsivity traits of young drivers. 209 participants aged between 17 and 25 completed questionnaires on their driving behaviours, impulsivity, and frequency of cannabis use. Results show that the frequency of cannabis use is a significant predictor of risky driving over and above the five impulsivity traits. Furthermore, positive urgency is the only impulsivity trait which predicts risky driving, regardless of the frequency of cannabis use. Several explanations of these results are proposed, including one we found particularly relevant: the probability of driving under the influence is higher with more frequent use, so the substance effects could explain risky driving behaviour. Therefore, in our second study, we wanted to test whether cannabis use was associated with risky driving behaviour even if the user was not driving under the influence. Moreover, since frequent use can be symptomatic of a cannabis use disorder (CUD), we wanted to verify its impact on risky behaviours. The second article, therefore, compares two groups of cannabis users (with or without CUD) on several driving behaviours, while considering their impulsivity. A sample of 76 male participants, cannabis users, aged 18 to 25, completed a driving simulation task and a stop-signal task, abstaining from cannabis use in the 12 hours preceding the experiment. They also completed questionnaires about their cannabis use patterns, impulsivity traits and risk-taking. Results show that users with a CUD displayed more risky behaviours in the simulator than users without a CUD, regardless of their impulsivity level and without being under the effects of the substance. Several explanations have been proposed: difficulty adjusting to driving without the influence of the substance for users with a CUD; presence of a confounding variable different from the impulsivity; or residual effects of cannabis, not detected by the stop-signal task. In summary, this thesis emphasizes that cannabis use is a contributing factor to young drivers’ risky behaviours, regardless of their impulsivity. Moreover, cannabis users are not a homogeneous group, which is why it is important to specifically target problematic users in prevention campaigns.

Self-regulation, the ability to guide behavior according to one’s goals, plays an integral role in understanding loss of control over unwanted behaviors, for example in alcohol use disorder (AUD). Yet, experimental tasks that measure processes underlying self-regulation are not easy to deploy in contexts where such behaviors usually occur, namely outside the laboratory, and in clinical populations such as people with AUD. Moreover, lab-based tasks have been criticized for poor test–retest reliability and lack of construct validity. Smartphones can be used to deploy tasks in the field, but often require shorter versions of tasks, which may further decrease reliability. Here, we show that combining smartphone-based tasks with joint hierarchical modeling of longitudinal data can overcome at least some of these shortcomings. We test four short smartphone-based tasks outside the laboratory in a large sample (N = 488) of participants with AUD. Although task measures indeed have low reliability when data are analyzed traditionally by modeling each session separately, joint modeling of longitudinal data increases reliability to good and oftentimes excellent levels. We next test the measures’ construct validity and show that extracted latent factors are indeed in line with theoretical accounts of cognitive control and decision-making. Finally, we demonstrate that a resulting cognitive control factor relates to a real-life measure of drinking behavior and yields stronger correlations than single measures based on traditional analyses. Our findings demonstrate how short, smartphone-based task measures, when analyzed with joint hierarchical modeling and latent factor analysis, can overcome frequently reported shortcomings of experimental tasks.