Impaired inhibition is a deficit of several psychopathological disorders, particularly attention-deficit hyperactivity disorder (ADHD). In the first study, a meta-analysis was conducted to determine whether impaired inhibition as measured by the Stop Signal Task is specific to ADHD, or whether it could be found in other psychopathological disorders. The meta-analysis found an inhibitory deficit in ADHD, but also in obsessive compulsive disorder (OCD) and schizophrenia (SCZ), suggesting that deficient inhibition is not specific to ADHD. A common neural mechanism may underlie deficient inhibition in ADHD, OCD, and SCZ. Study 2 aimed to determine the neural basis of inhibition using a lesion-deficit approach in children with traumatic brain injury (TBI). Only TBI children with white matter lesions in the superior frontal gyrus (SFG) region showed impaired inhibition compared with orthopedic injury controls. This suggests that deficient inhibition may stem from frontal lobe white matter damage, particularly in the SFG.

Impaired inhibition is a deficit of several psychopathological disorders, particularly attention-deficit hyperactivity disorder (ADHD). In the first study, a meta-analysis was conducted to determine whether impaired inhibition as measured by the Stop Signal Task is specific to ADHD, or whether it could be found in other psychopathological disorders. The meta-analysis found an inhibitory deficit in ADHD, but also in obsessive compulsive disorder (OCD) and schizophrenia (SCZ), suggesting that deficient inhibition is not specific to ADHD. A common neural mechanism may underlie deficient inhibition in ADHD, OCD, and SCZ. Study 2 aimed to determine the neural basis of inhibition using a lesion-deficit approach in children with traumatic brain injury (TBI). Only TBI children with white matter lesions in the superior frontal gyrus (SFG) region showed impaired inhibition compared with orthopedic injury controls. This suggests that deficient inhibition may stem from frontal lobe white matter damage, particularly in the SFG.

Compulsive eating behavior is a transdiagnostic construct observed in certain forms of obesity and eating disorders, as well as in the recently proposed ‘food addiction.’ Compulsive eating has been conceptualized as being comprised of three elements: i) habitual overeating, ii) overeating to relieve a negative emotional state, and iii) overeating despite adverse consequences. Neurobiological processes that include maladaptive habit formation, the emergence of a negative affect, and dysfunctions in inhibitory control are thought to drive the development and persistence of compulsive eating behavior. These complex psychobehavioral processes are under the control of various neuropharmacological systems. Here, we describe the current evidence implicating these systems in compulsive eating behavior, and contextualize them within the three elements. A better understanding of the neuropharmacological substrates of compulsive eating behavior has the potential to significantly advance the pharmacotherapy for feeding-related pathologies. / 2018-10-31T00:00:00Z

Prospective memory (PM) is the ability to remember to carry out one's intentions. This is a critical ability for children to develop in order to function independently in their daily activities. This dissertation examines the role of executive functioning in preschoolers' PM in two studies that vary the executive demand at different stages of the PM task. Study 1 investigated the role of task difficulty during the retention interval prior to the PM task. A difficult working memory task during the delay period resulted in worse PM performance in 4- and 5-year-olds compared to an easy working memory task. In addition, children's working memory, planning ability, and theory of mind correlated with PM but only in the difficult filler task condition. Study 2 examined age differences between 4- and 5-year-olds in PM task performance when the task: (1) was embedded in an easy or difficult ongoing task, (2) had an instruction to focus on the intention versus an instruction to focus on the distractor activity during the retention interval, and (3) varied in the salience of prospective targets. Overall, 5-year-olds performed better on the PM task than 4-year-olds. Children also had superior PM when targets were salient compared to non-salient and marginally superior PM when they received an instruction to monitor their intention compared to when they received an instruction to focus on the distractor activity. In addition, positive relations between executive functioning and PM were documented. Taken together, these studies suggest that disrupting or encouraging monitoring has a direct impact on PM performance in certain conditions. The implications of these results for theories that suggest differing roles for controlled processes in PM are discussed.

BACKGROUND: Early initiation of alcohol and other substance use is considered one of the most important risk factors for the later development of an alcohol use disorder. However, it is not yet well understood to what extent this increased risk reflects neurobiological changes driven by the use itself, and to what extent it reflects pre-existing traits and patterns. This dissertation therefore aims to identify neurobiological and neuropsychological markers that exist prior to the initiation of substance use and may confer risk for earlier use onset. Specifically, the research places a focus on the domains of inhibitory control and learning and memory. METHODS: Adolescents (n=81) were enrolled into the study prior to the initiation of alcohol or other drug use at 13-14 years old to complete baseline brain imaging. Neuroimaging included acquisition of structural magnetic resonance imaging (MRI) and task functional magnetic resonance imaging (fMRI) during response inhibition (emotional Go-NoGo) and spatial memory (virtual Morris Water Task) tasks. Participants also completed a neuropsychological battery that included the California Verbal Learning Test Children’s Version (CVLT-C). Subjects were then followed for up to three years via quarterly online surveys in order to assess initiation of alcohol and substance use. Those who went on to endorse initiating substance use prior to reaching 16 years of age were included in an initiating group (IG, n=21) and those who turned 16 having continuously denied substance use were included in a non-initiating comparison group (CG, n=24). RESULTS: Performance measures on the emotional Go-NoGo (NoGo trial accuracy, Go trial accuracy, Go trial reaction time) showed no significant group differences between IG and CG. Functional brain activation differences, however, were observed in bilateral inferior frontal gyrus (IFG), with CG showing greater activation relative to IG on inhibitory (NoGo) trials with negative versus neutral emotional background images (Negative NoGo>Neutral NoGo). Performance on learning trials for the virtual Morris Water Task, completed offline prior to scanning, showed a subtle learning difference between groups, but no performance or functional brain activation differences were observed on Retrieval or Motor control trials completed during scanning. Performance on the neuropsychological test of verbal learning and memory (CVLT-C) indicated worse learning and memory in IG relative to CG (fewer correct responses on both the Long-Delay Free-Recall and the Recognition trials). CONCLUSIONS: These findings help characterize neurobiological and neuropsychological patterns that exist prior to exposure to substances, and thus may help differentiate adolescents who go on to initiate substance use earlier in adolescence from those who do not. Results suggest brain activation differences in frontal regions may predate use, while activation differences in hippocampal memory systems (observed in some cross-sectional studies of alcohol use) may not. These data help clarify questions of causality and provide a foundation for informing strategies for prevention and intervention efforts in maladaptive alcohol and substance use.

Vibrations are often experienced in the workplace and may influence performance and executive function. Research has shown that vibrations may have an affect effect on drowsiness and tests related to inhibitory control. Previous work investigating whole body vibrations (WBV) and their effect was evaluated to inform the decisions for this study. WBV effects on cognitive abilities were examined and the different tests used in these studies were identified and compared. Electroencephalogram (EEG) and event related potentials (ERP) were selected to be used to measure inhibitory and cognitive processes. The N2 ERP, which reflects inhibitory control processes, was examined as well as the dominant frequency of the Fourier fast transform (FFT). A total of 94 participants between the ages of 18-55 (Mage = 20.49 SDage = 1.68) completed this study (51 female, 38 male and 5 with no gender listed). A go/no-go task was used to elicit the N2 ERP after WBV and a simultaneous EEG recording while the participants experienced WBV was used to gather the needed data. Stimulus frequencies used for the N2 ERP included 15 Hz, 20 Hz, and 40 Hz. During the simultaneous recording stimulus frequency varied every 30 seconds by 10 Hz from 20 Hz to 110 Hz. Data were analyzed using both a linear mixed effects model for normally distributed data and a generalized linear mixed effects model for data taken as percentages. It was hypothesized that there would be an effect on performance as measured in the raw go/no-go results, that this change in performance showing improved accuracy would be linked to inhibitory control, and be seen as a decrease in the magnitude of the N2 ERP. It was also hypothesized that the exploratory FFT portion of the study would produce a shift from a higher to a lower frequency in the dominant waveform . The results show that there were no main effects in either the behavioral performance or in the N2 ERP of the participants but that there was a significant interaction at 40 Hz with improved simple go trial activity and decreased no-go inhibition. The results also show that there was a statistically significant shift in neural oscillation activity but that this shift was not real-world relevant within the context of this study.

Temperamental self-regulation is typically associated with adaptive outcomes, but considerably less is known about the correlates of rudimentary self-regulation—regulatory capacity—in infancy. Some theoretical frameworks also suggest that low and high levels of inhibitory control—one component of temperamental self-regulation—may be related to negative outcomes, and further that this may depend on individual differences in shyness. In this dissertation, I examined the functional correlates of infants’ regulatory capacity moderated by physiological regulation (Chapter 2), the negative consequences of low and high levels of inhibitory control on preschoolers’ social and psychological outcomes (Chapter 3), and the social (Chapter 4) and contextual (Chapter 5) factors modifying the impact of inhibitory control on shy children’s interpersonal outcomes. In Chapter 2, I found that infants’ regulatory capacity was only negatively related to behavior problems when infants displayed high levels of physiological regulation during an emotionally salient stressor. In Chapter 3, I found that very low and high levels of inhibitory control were related to the highest levels of avoidant social behavior and internalizing and externalizing problems in preschoolers. In Chapter 4, I found that preschoolers’ shyness was only negatively associated with their own observed approach behavior when their own inhibitory control was high (actor effects), and this pattern of results differed when examining the partner’s observed behavior (partner effects). In Chapter 5, I found that shyness was negatively associated with social support seeking when preschoolers displayed high levels of inhibitory control in an unfamiliar context, and this pattern of results differed in a familiar context. These studies challenge the longstanding belief that self-regulatory processes are adaptive for all children all the time, and suggest that developmental, temperamental, and contextual factors may influence whether self-regulation acts as a resiliency or risk factor. / Dissertation / Doctor of Philosophy (PhD) / Self-regulation refers to children’s ability to control their behavior and attention to achieve goals and is an important part of personality. Although self-regulation is typically associated with positive outcomes during the preschool period, less is known about the consequences of self-regulation during infancy, and some research has suggested that low and high self-regulation may have negative consequences for children. In this dissertation, I examined whether physiological regulation during infancy influenced the relation between self-regulation and behavior problems, and then I examined whether low and high levels of self-regulation are associated with children’s problematic social and psychological outcomes and whether these relations depend on children’s shyness and their social partner’s characteristics. Together, this work challenges the belief that self-regulation is always protective for all children all the time and suggests that personality and contextual factors may determine whether self-regulation acts as a protective or a risk factor.

Yes / This study examined whether the proposed bilingual advantage in inhibitory control and working memory can be extended to a trilingual advantage, and assessed any age-related effects on a continuum in young adults to older adults. Trilinguals, bilinguals and monolinguals’ performance on the Simon task and a numerical version of the N-back task was compared. On the Simon task, there was no language group difference observed, although the data show an age-related decline in inhibitory control only in trilinguals, but not in bilinguals or monolinguals. No clear language group differences were observed between trilinguals and bilinguals on the N-back task, however an overall trilingual and bilingual disadvantage, compared to monolinguals, was observed. Together the results suggest that managing two or three languages, compared to just one, may have a negative impact on inhibitory control and working memory performance. Importantly, they highlight the need to control for a possible confounding effect of including trilinguals/multilinguals in bilingual cohorts and to ensure that participants in monolingual cohorts speak only one language.

Social cognition is a set of complex processes that mediate much of human behavior. The development of these skills is related to and interdependent on other cognitive processes, particularly inhibitory control, which allows for willful suppression of dominant responses. Many aspects of social behavior rely on inhibitory control to moderate impulsive or socially inappropriate behaviors and process complex perspective-taking. Furthermore, the brain regions associated with inhibitory control and social cognition overlap functionally and structurally. I review neurodevelopmental literature to suggest that social cognition is developmentally dependent on inhibitory control and that the neural foundations of both these skills are measurable in infancy. I tested this model using growth curve and structural equation modeling and show that 10-month, but not 5-month, frontotemporal coherence predicts social cognition in late childhood through preschool inhibitory control. These findings provide insight into the neurodevelopmental trajectory of cognition and suggest that connectivity from frontal regions to other parts of the brain is a foundation for the development of these skills. / Doctor of Philosophy / Social cognition is the ability to understand and interpret another’s thoughts, words, and actions and inhibitory control is the ability to suppress one’s own thoughts, words, and actions. These two types of cognition are similar and use the same brain regions, and I suggest that inhibitory control underlies much of social cognition. In order to test this, I examined children’s inhibitory control and brain connectivity at 5 months, 10 months, 24 months, 48 months, and 9 years and measured social cognition at 9 years. I found that connectivity between the frontal and temporal lobes at 10 months predicted inhibitory control and 48-months, which then predicted social cognition at 9 years. This suggests that infant brain connectivity sets the stage for developing inhibitory control, which is important for later social cognition

An interactive framework of working memory and inhibitory control has been endorsed for examining cognitive development across the lifespan (Roberts & Pennington, 1996). According to this framework, the interaction between working memory and inhibitory control (WMIC) is necessary for adaptive daily functioning (Roberts & Pennington, 1996) and crucial for the development of executive functioning in childhood (Brocki & Bohlin, 2004). Empirical work from early developmental periods supports the interactive WMIC framework (e.g., Bell, 2001; Diamond, Kirkham, & Amso, 2002) and has identified sources of variability (brain electrical activity, temperament, and language) associated with WMIC functioning in infancy and early childhood (Wolfe & Bell, 2004). Although there is some evidence to suggest the interdependent nature of working memory and inhibitory control in late childhood and adulthood (Diamond, 2002; Luna, Garver, Urban, Lazar, & Sweeney, 2004), work in these later developmental periods has focused primarily on the independent processes of working memory (WM) and inhibitory control (IC) and the interactive WMIC framework has not been directly investigated from late childhood onward. Therefore, the first goal of the current study was to examine the interactive framework in a late childhood sample. The second goal of the study was to examine sources of variability in WMIC functioning in late childhood, with the intention of determining which sources of variability were associated with and contributed unique variance in explaining WMIC performance. Thirty-eight children (19 male) completed four age-appropriate interactive WMIC tasks (the color-word Stroop, the Fruit Stroop, the counting go/no-go and the Wisconsin Card Sort Test) and two language tasks. Both parents and children responded to a temperament questionnaire. Brain electrical activity was collected via EEG recordings during a two-minute baseline and WMIC tasks. The four interactive WMIC tasks were tested for relation of the independent (WM, IC) and combined (WMIC) components within tasks and across tasks. The four WMIC tasks were not correlated with one another. However, the independent (WM, IC) components were correlated both with one another and with the combined WMIC measure within each task, providing some support for an interactive framework in late childhood. The sources of variability associated with the independent (WM, IC) and combined (WMIC) components of each task were identified. These sources were used to explain both collective and unique variance in WMIC functioning for each task. Different sources of variability explained independent (WM, IC) and combined (WMIC) performance across tasks. Unique and shared contributors within and across tasks (the color-word Stroop, the Fruit Stroop, the counting go/no-go and the Wisconsin Card Sort Test) and components (WM, IC, WMIC) are discussed in an effort to determine how sources of variability may be related to WMIC functioning. / Ph. D.