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Current theoretical models of ADHD (i.e., Disinhibition Model: Barkley, 1997; Working Memory Model: Rapport et al., 2001) conceptualize ADHD as the disorder of executive function (EF) with some variation in their emphases on particular components of the broadly-defined EF (e.g., working memory vs. inhibition) and in their postulated relationships with ADHD symptoms. Although these models provide systematic accounts of the manifestation of ADHD, they have not been extensively tested from an empirical standpoint. Moreover, despite the fact that ADHD is highly comorbid with other additional conditions such as learning and behavioral problems and EF deficits are found in individuals with these conditions as well as in those with ADHD, current EF models have not specified the developmental relationship between ADHD and its comorbid conditions. This study was: (1) to examine the extent to which two current models of ADHD are supported in a sample of 102 adults; (2) to present an ??integrated?? model by combining two current models of ADHD and linking them to recent research findings on two common comorbid conditions with ADHD (i.e., reading difficulty and substance abuse); and (3) to test and revise such an integrated model in the light of data using a latent variable analysis. Major findings provided a strong support for the Working Memory Model with a lesser degree of support for the Disinhibition Model. Preliminary evidence of working memory as the primary deficit in ADHD was also obtained in the present sample. Finally, the integrated EF model and its revised model (final model) demonstrated a very good fit to the data. These findings suggest that the integrated model provides a unified account of how EF deficits contribute to the manifestation of ADHD symptoms and comorbid conditions with ADHD. Given some limitations (e.g., sample size and scope) of the present study, current findings need to be replicated.

This study examines the roles of inhibition, attention, working memory, and planning in youth with and without ADHD. As conceptualized in theories of attention, inhibition, and working memory, difficulties with these executive processes interact to manifest in the behavioral syndrome(s) of ADHD. Barkley (1997) proposed disinhibition as the primary deficit of ADHD. Rapport, Chung, Shore, Denney, & Isaacs, (2000) theorized that ADHD results from a primary deficit in working memory. Mirsky (1987) proposed a model of attention which children with ADHD have deficits in abilities to focus/execute, encode and sustain attention. Posner and Petersen (1990) proposed that three attentional networks are responsible for attentional processes and those children with ADHD have deficits in the vigilance network. To investigate the contributions of inhibition, working memory, attention, and planning in executive dysfunction in children with ADHD, measures were selected from factor analytic studies. Children with ADHD-Combined Type demonstrated poorer inhibition and working memory than children with no diagnosis after controlling for IQ effects. No differences in planning and attention were indicated after controlling for IQ effects. However, a predictive discriminant analysis indicated that none of the executive processes contributed to the prediction of group membership. Given correlational and predictive discriminant analysis results, further analyses were conducted to investigate the contribution of the measures selected for the domains. The theoretical model did not represent a good fit of the data. A three-factor model indicated the best representation suggesting that inhibition and attention were not separable. There were no group differences with the revised measurement model for inhibition/attention, working memory and planning. Taken together, results indicated measures originally selected to tap executive function may not be clean measures of inhibition, working memory, planning, or attention processes. In addition, recently proposed theories overlap and conceptualize the multiple constructs involved in ADHD with a variety of methodologies, further contributing to difficulties in interpreting results and measurement issues.

Theories that formally describe decision-making have traditionally posited that decisions are made by rational actors. However, it is generally accepted that humans often make irrational decisions because of quick emotional judgements. In order to reconcile these two inconsistent ideas psychologists have developed two-system theories that hypothesize decisions are made by two opposing cognitive systems, representing the rational and emotional processing of decisions. Evidence for a two-system model of decision-making can be observed in ultimatum game responder decisions. It is thought that rational processing of these choices will produce acceptance of unfair offers and emotional processing will encourage rejection of unfair offers. Emotional priming has been shown to decrease ultimatum game acceptances and trans-cranial magnetic stimulation of rational brain areas, i.e. DLPFC, show increases in ultimatum game acceptances. This study investigated the possibility of using behavioral tasks that are known to activate rational brain areas to promote/disrupt ultimatum game acceptances. The possible relationship between ultimatum game acceptances and executive functions was also examined. Although there were promising indications that working memory loading may increase ultimatum game acceptances in between-subject experiments, a within-subject investigation found little support for this method of promoting/disrupting rational ultimatum game decisions. There were also no relationships found between switching or inhibition executive functions and ultimatum game responder decisions. A moderate positive relationship was found between updating executive function and ultimatum game acceptance rates but this relationship was dependent on working memory task feedback, a within-subject design and active loading of the working memory system. However, its possible that these findings only apply to within-subject paradigms and future between-subject studies are advised.

Introduction. Executive function refers to the top-down neurocognitive processes involved in flexible, goal-oriented behavior. A number of studies have shown positive effects of EF training. The overall aim of these studies was to explore the neurocognitive processes that support the development of EF by understanding how EF training works and what the active ingredients are. Particular interest was in isolating the role of reflection in EF training to understand its top-down affect on ACC-mediated conflict detection. Method. In Exp. 1 the neural markers of EF were explored by comparing ERPs of preschoolers who passed the DCCS and preschoolers who failed. Exp. 2 represents an attempt to replicate the key findings of Kloo & Perner, (2003, Exp. 2) that reflection training improves preschoolers’ performance on the DCCS and demonstrates far transfer. A shortened version of the training protocol was also tested (Exp. 3). In Exp. 4, the neural correlates of reflection training in preschoolers were explored by examining changes in the neural marker of EF found in Exp. 1. Results. In Exp. 1, the N2 amplitude was smaller (less negative) for children who passed the DCCS and were able to efficiently resolve the conflict in the stimuli than for children who failed and were unable to resolve the conflict. Exp. 2 replicated the findings of Kloo & Perner, (2003, Exp. 2) even using a brief (15 min) intervention targeting reflection (Exp. 3). In Exp. 4, one brief session of reflection training made children who initially failed the DCCS look like children who initially passed at both the behavioral and neural level (reduced N2 amplitude). Conclusion. Results suggest that reflective processing facilitates the development of EF in young children by teaching them to notice conflict, reflect on it, and formulate rules for resolving it, resulting in the down-regulation of ACC-mediated conflict detection.

Introduction. Executive function refers to the top-down neurocognitive processes involved in flexible, goal-oriented behavior. A number of studies have shown positive effects of EF training. The overall aim of these studies was to explore the neurocognitive processes that support the development of EF by understanding how EF training works and what the active ingredients are. Particular interest was in isolating the role of reflection in EF training to understand its top-down affect on ACC-mediated conflict detection. Method. In Exp. 1 the neural markers of EF were explored by comparing ERPs of preschoolers who passed the DCCS and preschoolers who failed. Exp. 2 represents an attempt to replicate the key findings of Kloo & Perner, (2003, Exp. 2) that reflection training improves preschoolers’ performance on the DCCS and demonstrates far transfer. A shortened version of the training protocol was also tested (Exp. 3). In Exp. 4, the neural correlates of reflection training in preschoolers were explored by examining changes in the neural marker of EF found in Exp. 1. Results. In Exp. 1, the N2 amplitude was smaller (less negative) for children who passed the DCCS and were able to efficiently resolve the conflict in the stimuli than for children who failed and were unable to resolve the conflict. Exp. 2 replicated the findings of Kloo & Perner, (2003, Exp. 2) even using a brief (15 min) intervention targeting reflection (Exp. 3). In Exp. 4, one brief session of reflection training made children who initially failed the DCCS look like children who initially passed at both the behavioral and neural level (reduced N2 amplitude). Conclusion. Results suggest that reflective processing facilitates the development of EF in young children by teaching them to notice conflict, reflect on it, and formulate rules for resolving it, resulting in the down-regulation of ACC-mediated conflict detection.

Behavioral evidence has shown that older adults are less able to overcome proactive interference in memory than young adults. However, it is unclear what underlies this deficit. Imaging studies in the young suggest overcoming interference may require post-retrieval selection, a process thought to be mediated by the left mid-ventrolateral prefrontal cortex (VLPFC). Further, selection may resolve interference by enhancing or suppressing perceptual processing. The present fMRI study investigated whether age-related changes in VLPFC-mediated post-retrieval selection underlie older adults' deficits in overcoming interference in associative memory. Participants were tasked with remembering which associate (face or scene) objects were paired with most recently during study, under conditions of high or low proactive interference. Behavioral results demonstrated that as interference increased, memory performance decreased similarly across groups. Across groups, activity in the left mid-VLPFC also increased with interference. However, right PFC post-retrieval monitoring effects, but not left mid-VLPFC, distinguished successful vs. unsuccessful resolution of interference for both young and older adults, suggesting selection alone may be insufficient for successful resolution of interference. Age-related memory deficits may be related to reduced recruitment of relational processing effects in the dorsolateral and anterior PFC, as well as reduced memory retrieval effects in the hippocampus. Lastly, results showed evidence that selection may modulate perceptual processing of retrieved memory representations. Namely, activity in the parahippocampal place area (PPA) was greater when participants selected scene, versus face, regardless of accuracy. Further, older adults showed reduced effects in the PPA, possibly reflecting reduced differentiation of perceptual processing. Taken together, these results suggest age-related deficits in overcoming proactive interference are not related to post-retrieval selection, but reduced recruitment of PFC-mediated relational processes, coupled with reduced associative memory retrieval.

Background: Prenatal alcohol exposure causes behavioural, growth and central nervous system deficits in the offspring, termed Fetal Alcohol Spectrum Disorder (FASD). Our lab has previously shown that structured saccadic eye movement tasks probe executive functioning and can be used to measure cognitive dysfunction in children with an FASD, because performance of these tasks reflects the structural integrity of brain areas shown to be vulnerable to prenatal alcohol exposure. Recently developed portable electroencephalographic (EEG) devices record brain activity using a single dry-sensor electrode. Our objectives were: 1) to assess attention and working memory via a delayed memory-guided saccadic eye movement task of varying mnemonic load and 2) to explore the use of a portable single-channel EEG recording device in measuring differences in frontal lobe activity in children with FASD during the performance of this eye movement task. Methods: A total of 18 children with an FASD diagnosis and 19 typically developing control children performed a memory-guided saccadic eye movement task with one, two or three target stimuli. During the task, frontal lobe EEG was recorded using the Neurosky Mindwave Mobile® portable recording device. Results: In the delayed, memory-guided task when two or three target stimuli were required to be held in working memory, children with an FASD performed the task correctly less often than children in the control group. During task performance, children with FASD exhibited a reduction in theta frequency band power, and in alpha frequency band power only at higher mnemonic loads, suggesting that children with FASD recruited more cognitive resources to complete the task. Conclusion: The results of this study suggest that a portable EEG recording device can be used to assist in the recognition of underlying neural mechanisms of executive functioning deficits in children with FASD. Portable devices offer greater user comfort than typical EEG recording equipment as well as flexibility for use outside the laboratory. This could greatly facilitate the study of children with FASD, and other groups who may be less tolerant of typical laboratory environments. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-08-14 20:22:10.995

The capacity to mentally project the self into the future or, what has recently been termed “episodic foresight” is an emerging topic of study in developmental psychology. The aim of this dissertation was to review available research on this topic and explore its development in two groups of children: typically-developing preschoolers and children with autism spectrum disorder (ASD). This dissertation had two main goals. The first goal was to explore whether tasks thought to measure episodic foresight in children are related and whether, as has been hypothesized, they were related to theory of mind (ToM) and executive function (EF). Study 1 showed that after controlling for age and language ability, episodic foresight tasks were not intercorrelated, nor were they individually related to ToM or EF tasks. Importantly, however, an episodic foresight composite score was related to several EF tasks. Specifically, the results suggested a significant relation between episodic foresight and inhibitory control. The second goal of this dissertation was to explore the development of episodic foresight in children with ASD. Specifically, I tested whether children with ASD would perform more poorly on a series of episodic foresight tasks than a mental-age matched group of typically-developing children. Study 2 revealed significant group differences on several episodic foresight tasks, suggesting that children with ASD showed impairments in thinking about themselves in the future. These results are a timely contribution to the research on episodic foresight and will hopefully aid in the further development of tasks that adequately measure this important cognitive ability in children.

In early childhood, planning provides a basis for organizational skills that are useful for future school performance (Perez & Gauvain, 2009). However, research shows that preschoolers’ planning abilities are limited because they often fail to consider task demands, are inefficient at self-monitoring, and are unlikely to use strategies to their advantage (Gardner & Rogoff, 1990). The present study examined whether preschoolers could improve their planning skills by consciously drawing connections between objects and events through the use of verbal self-explanations. A microgenetic design was used in order to repeatedly measure preschoolers’ performance on the Tower of Hanoi (ToH) task over a period of 6 to 8 weeks. Forty-five children between the ages of 4 and 6 years were randomly assigned to 1 of 3 conditions: self-explanation, no self-explanation, and control. Each child was administered a pretest, 3 micro sessions based on condition, and a posttest. In addition to ToH performance, children also were measured on inhibitory control, working memory, short-term memory, and verbal ability at pretest, and on a novel planning task, the Box-ToH, at posttest. Multilevel models were used to analyze the data at the between- and within-person levels. Although no differences were found in ToH performance over time between conditions, preschoolers’ use of self-explanations and strategies were independently related to individual improvements in ToH performance over time. Moreover, preschoolers’ improvements in ToH performance were not reducible to age-related increases, inhibitory control demands, working memory, short-term memory, or verbal ability. Lastly, findings did not support preschoolers’ ability to transfer their knowledge of strategies on the ToH to the Box-ToH. Overall, the present study demonstrated that self-explanations and strategy use are both important predictors of understanding individual changes in planning performance during the preschool years. These findings have important implications in terms of improving preschoolers’ executive function skills and preparing children for early academic success. / Graduate