Issued also as Thesis (Ph. D.)--Columbia University. / Bibliography: p. 40-41.

Following exposure to consistent stimulus–stop mappings, response inhibition can become automatised with practice. What is learned is less clear, even though this has important theoretical and practical implications. The main contribution of this thesis is to investigate how stimulus-stop associations are acquired and the conditions under which they influence behaviour. To this end, this thesis addressed several outstanding issues concerning the associative architecture of stop learning, the role of expectancies, and the specificity of learning in inhibition tasks. Experiments 1-4 provide evidence that participants can acquire direct associations between specific stimuli and the stop goal without mediation via a single representation of the stop signal. However, these experiments also suggest that the influence of stimulus-stop associations on behaviour depends on top-down attentional settings: if participants begin to ignore the stop-associated stimuli, the effects of stop learning are diminished or eliminated entirely. Across eight experiments, this thesis provides evidence that participants generate expectancies during stop learning that are consistent with the stimulus-stop contingencies in play. However, Experiments 5-6 indicate that there may be some differences in the relationships between stimulus-stop expectancies and task performance under instructed and uninstructed conditions; stimulus-stop associations that are acquired via task instructions or via task practice have similar effects on behaviour, but seem to differ in how they trigger response slowing for the stop-associated items. Experiments 7-8 investigated the role of signal detection processes during the acquisition of stimulus-stop associations. To distinguish between stimulus-stop learning and stimulus-signal learning, the contingencies between specific stimuli and the stop goal and the contingencies between specific stimuli and the spatial location of the stop signal were independently manipulated. Although these experiments showed evidence of stop/go (goal) learning, there was no evidence that participants acquired the stimulus-signal associations. Across four experiments, this thesis investigated the specificity of stop learning. Experiments 9-10 compared the effects of training on behavioural performance in inhibition (go/no-go) and non-inhibition (two-choice) tasks. The results of these experiments revealed that learning in inhibition and non-inhibition tasks could arise through similar associative mechanisms, but suggest that the effects of training in these tasks could also depend on top-down response settings and general non-associative processes. Experiments 11-12 investigated the neural specificity of stop learning. These experiments also revealed similar effects of training across the go/no-go and two-choice tasks adding weight to the claim that training in inhibition tasks primarily influences task-general processes. Combined, the overall conclusion of this thesis is that bottom-up control can influence response inhibition but what is learned depends on top-down factors. It is therefore important to consider bottom-up factors and top-down factors as dependent, rather than independent, influences on response inhibition.

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Under frameworks such as Alcohol Myopia Theory, a body of literature has developed demonstrating how alcohol intoxication can increase behavioral risk-taking, potentially via impaired inhibition of prepotent behavioral responses. A separate area of research has shown that responses to alcohol intoxication are not homogenous across the population. Whereas most previous research has considered alcohol responses in relation to risk for alcohol use disorders, the present investigation tested whether they may additionally contribute to the acute effects of alcohol on drinking-episode-specific cognitive and behavioral consequences. We recruited 82 moderate-to-heavy drinking emerging adults to each complete 2 research protocols: a placebo-controlled, within-subject, counterbalanced alcohol challenge in a simulated bar laboratory and a 21-day, event-level self-monitoring follow-up. Replicating previous research, the alcohol challenge increased heart rate and subjective stimulant-like and sedative-like responses and impaired psychomotor performance and response inhibition. Individual differences in subjective stimulation but not sedation were significantly associated with inhibitory impairment. In the event-level follow-up, we found little evidence that alcohol responses elevated risk for adverse behavioral outcomes, although evidence was stronger that alcohol responses were associated with alcohol-induced memory blackout. Whether and how alcohol responses relate to the physiological, cognitive, and behavioral consequences of alcohol intoxication may depend on a) the quality of the response (e.g., stimulation vs. sedation), b) the type of outcome (e.g., response inhibition vs. blackout vs. behavioral risk-taking), and c) whether perceptions of alcohol-induced effects may contribute to emerging adults' evaluations of risk (e.g., driving after drinking and riding with a drinking driver). / text

Action control arises from the interaction of two anatomically distinct decision-making systems, namely goal-directed and habitual behaviour. Goal-directed behaviour is characterized by the consideration of future choices and respective outcomes whereas habitual responding is driven by stimulus-response associations. Response inhibition is essential for goal-directed behaviour and deficits are shown in impulsivity. We administered an acute clinically relevant dosage of the commonly used serotonin reuptake inhibitor escitalopram to sixty-six healthy volunteers in a double-blind, randomized, placebo-controlled design. We administered a large task battery in order to study the effect of escitalopram in several cognitive functions including response inhibition, learning and affective processing. We found dissociate effects on cognitive aspects possibly mediated by distinct cortico-striatal loops. Acute escitalopram administration had a beneficial effect on action cancellation, one aspect of inhibitory control, without any effect on action restraint or waiting impulsivity. The treatment resulted in impaired performance in a probabilistic reversal-learning task and increased sensitivity to misleading feedback thus leading to maladaptive performance. An extra-dimensional set shift impairment during an attention set shift task and a tendency towards impaired instrumental learning discrimination were also observed in the escitalopram group. Our results are discussed in the context of well-documented effects of the dopaminergic system and suggestions of opponent interaction of serotonin and dopamine.

Heavy episodic drinking is linked with poorer academic performance, injury, and risk behaviors among college students. Understanding the cognitive and motivational factors that influence self-control of alcohol use is critical to identifying students' risk factors and developing interventions. Dual process models characterize alcohol use patterns as a function of automatic appetitive responses to alcohol-related stimuli and executive control functions. These processes may be influenced by contextual cues such as mood. The present research sought to better understand the cognitive-motivational mechanisms through which an established contextual cue for drinking - positive mood - influences alcohol use. Two studies examined the influence of positive mood induction on undergraduate drinkers' approach biases for alcohol cues and executive functioning using established and modified Stimulus Response Compatibility Tasks (SRC). Undergraduates who used alcohol at least once in the past month were recruited from the introductory psychology subject pool and randomized to positive or neutral mood induction conditions to determine whether positive mood: (1) increased approach bias or (2) impaired efforts to control alcohol cue responses. Prior to mood induction, participants completed individual difference measures related to alcohol use to evaluate potential moderators. Experiment 1 (N=93) examined post-induction alcohol approach bias and approach response inhibition using a stop-signal task within SRCs. Those in the positive mood condition did not exhibit greater approach bias or less inhibition, and mood effects were not moderated by individual differences as hypothesized. Experiment 2 (N=141) examined the influence of mood on approach bias and the ability to reverse established SRC responses to alcohol cues, with a pre-induction SRC to control for baseline approach biases. Again, positive mood did not significantly influence alcohol approach bias or executive control. Discussion: Results did not support positive mood influences on cognitive-motivational processes associated with drinking. The absence of mood effects may be a function of the type of positive mood induced or sensitivity of the SRC to detect alcohol-specific approach bias in this population. Future studies should explore these processes using alternate measures of alcohol-specific approach bias, response inhibition, and mood states that may be more specific to drinking.

The present study investigates the effects of cognitive inhibitory mechanisms and tendency to suppress thoughts on the frequency and intensity of traumatic intrusions within the trauma film paradigm. Non clinical participants&rsquo / response inhibition and proactive inhibition levels and tendency to suppress thoughts were measured prior to exposure to a trauma film. One week after seeing the trauma film, participants reported the frequency and intensity of trauma film related intrusions with an intrusion diary and Impact of Events Scale. No significant effect of response inhibition, proactive inhibition and thought suppression tendency was found on the frequency and intensity of trauma film related intrusions. Findings of the study are discussed.

The purpose of this study was to determine if fitness levels of individuals affect cognitive function. This study seeks to show how response inhibition and accuracy are affected following a mentally fatiguing task. Response inhibition refers to the suppression of actions that are inappropriate and that interfere with goal driven behavior. Response inhibition in reference to the continuous performance task (CPT) is measured in false clicks. The tasks for the CPT were completed after either a controlled period of rest or moderate-intensity exercise. Subjects were either Georgia Tech Division I track athletes or students leading a sedentary lifestyle. All subjects participated in two test protocols. Athletic subjects completed the resting protocol first, while sedentary subjects completed the exercise protocol first. Subjects reported to the lab following an overnight fast. They completed an initial set of paper work and signed a consent form, filled out a 24 hour history form and completed a Profile of Moods States (POMS) and Visual Analog Scale (VAS) form. Subjects then took a 20-minute (CPT). The CPT is a neuropsychological test that measures an individual’s sustained and selective attention. The length of the test is 20 minutes in order to induce mental fatigue. The goal of the test is to click in a white box when the letter T is seen. Immediately after subjects filled out a secondary set of paperwork. Once paper work was complete subjects either rested or exercised for 35 minutes. If subject was classified as an athlete, trial 1 was rest, while trial 2 was exercise. If subject was classified as a sedentary student, trial 1 was exercise, and trial 2 was rest. After the subject completed either the cycling or resting portion they repeated the CPT for five minutes. It was hypothesized that that the effects of moderate exercise positively affect the subject’s performance on the CPT. I expect false clicks following the 5 minute CPT to be lower after exercising. I hypothesize that for both groups their accuracy should be higher after moderate cycling and that higher fitness level should decrease the level of mental fatigue experienced throughout the CPT.

An unresolved issue exists in the study of mental ability: which aspect of cognition is responsible for the emergence of psychometric “g” (Spearman, 1904, 1927), a general factor that predicts performance in all kinds of cognitive tasks and many important life outcomes? On the basis of themes present in the literature on fluid intelligence (Chapter 1), this thesis explores the relative contributions of processing, storage, and task modelling demands to the recruitment of g in task performance. Six experiments are presented which employed two computer-based tasks. The tasks were designed such that the level of demand for processing and storage was separated and manipulated in order to establish their relationship to scores on a standard test of g. Task manipulations were implemented in the context of varying the number of distinct verbal chunks in which task instructions were presented, whilst controlling for the presented amount of operative task-relevant information. The findings showed that the recruitment of g in task performance was strengthened by the presence (versus the absence) of a requirement to inhibit a prepotent response tendency (Experiments 1, 2, and 3), and by the presence of requirements to inhibit a prepared response and to maintain and update information in working memory (Experiments 4 and 5). However, these effects were observed only when task instructions were presented as four (and not as two) distinct rules. Additional findings showed that reconceptualisation of task requirements—that is, flexibly imposing order on a complex set of instructions thus reducing the number of distinct verbal chunks—was dependent on performance on the test of Spearman’s g (Experiments 3 through 6). These findings are deemed consistent with a task conceptualisation theory of g, with real-time execution demand, particularly inhibition, posing as a risk factor for the recruitment of g only when task requirements are maintained in mind as a relatively large number of chunks or rules.

Sedentary behaviors, such as leisure time computer use and sedentary video games, are significant barriers to regular physical activity and contribute to high rates of overweight and obesity among adolescents. Sedentary screen time can adversely affect food intake and food selection. Active video games may be a promising way of increasing daily physical activity levels among adolescents. Active video games may help modulate response inhibition and food intake. PURPOSE: Compare the effects of an acute bout of active and sedentary video gaming on N2 amplitudes (while viewing high calorie and low calorie images), Stroop Color Word Test (Stroop test) performance and ad libitum eating. METHODS: We used a within-subjects randomized crossover design with counterbalanced treatment conditions was used among 65 participants (31 girls, 34 boys; age = 13.5 ± 1.1 year; height = 161.4 ± 10.2 cm; weight = 52.5 ± 12.3 kg; BMI = 19.9 ± 3.3 kg·m2). Participants completed 2 separate video gaming sessions, 7 days apart, while energy expenditure during sedentary and active video game play was measured using the K4b2 portable metabolic system. The K4b2 system provided metabolic equivalents (METs) which are used as a measure of energy cost of physical activity. After either 60 minutes of active or sedentary video game play, participants completed a go/no-go task while viewing high calorie and low calorie images while electroencephalogram (EEG) data were collected. N2 event related potential (ERP) amplitudes were measured during the viewing task. Participants also completed a Stroop task to measure response inhibition. Finally, participants were given high calorie and low calorie snacks to consume ad libitum. We used a repeated measures ANOVA was used to measure main and interaction effects for N2 ERP amplitudes within subjects. RESULTS: Active video game play relative to sedentary video games significantly increased METs (F = 543.1, p ‰¤ 0.0001) from 1.7 ± 0.35 to 5.0 ± 1.2 METs. A significant gender-by-condition interaction (F = 7.03, p ‰¤ 0.009) was observed for energy expenditure with boys (5.4 ± 1.1 METs) expending more energy during the active video game than girls (4.5 ± 1.1 METs). No significant differences were observed for the N2 component (F = 0.50, p = 0.48) between video game conditions nor between genders (F = 1.85, p = 0.17). There were no significant differences (F = 3.10, p = 0.08) in the total number of calories consumed between the 2 video gaming conditions. Results from the Stroop task showed no significant differences for word naming (F = 0.45, p = 0.49), congruent condition (F = 0.43, p = 0.52) and incongruent condition (F = 0.14, p = 0.71) between the active and sedentary video games. CONCLUSION: Sixty minutes of active video gaming increases energy expenditure to a moderate intensity level but does not alter behavioral response or response inhibition to high calorie or low calorie foods.