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.

The 2002 Supreme Court decision (Atkins vs. Virginia, 536 U. S. 304), prohibiting the execution of mentally retarded persons, may potentially increase malingering of mental retardation (MR). There is limited research addressing the detection of feigned MR. The present study compared results from tests of intelligence, adaptive functioning, legal/courtroom knowledge, and psychiatric and neurocognitive feigning to determine how effectively these instruments discriminate between MR participants and community volunteers asked to either approach the test honestly (CVH group) or feign, or malinger, MR (CVM group). CVMs suppressed their IQ scores sufficiently to appear MR. CVMs overestimated deficits on individuals with genuine MR on tests of adaptive functioning and courtroom knowledge. Psychiatric feigning instruments did not discriminate between MR and CVM groups. Neurocognitive feigning instruments discriminated between groups, however specificity and Positive Predictive Power were unacceptably low. Revising cutting scores to hold specificity at .95 improved PPP significantly, suggesting the potential utility of these instruments to detect feigned mental retardation. Results from this study suggest that applying published decision rules to MR populations on tests commonly used in forensic neuropsychological evaluations will likely result in a high rate of false positive errors. Given the high stakes associated with classification errors in capital cases involving MR defendants, alternative cutting scores appropriate for this population should be determined.

The issue of effortful patient performance has been an area of clinical interest in individuals with minor traumatic brain injury (mTBI). Clinical attention to this area has increased largely because of an increase in the number of worker's compensation claims, injury-related lawsuits and/or insanity defense pleas. As patients are presented with the opportunity for secondary gain, the issue of optimum performance on neuropsychological measures becomes salient. In addition to neurocognitive deficits, there are psychological characteristics associated with mTBI including depression, emotional disturbance, personality changes, and other psychopathology. This study utilized the MSVT, a set of standard neuropsychological instruments, and the Minnesota Multiphasic Inventory-2 (MMPI-2) to investigate the relationships between effort, psychological characteristics, and neuropsychological functioning in individuals with minor traumatic brain injuries. The first objective of this study was to determine which psychological factors were related to effort in mTBI. The second objective was to determine if there were differences between groups that performed poorly on effort testing and groups that performed adequately on effort testing, based on relevant psychological characteristics. The results of the analyses supported the first hypothesis. Hysteria was inversely related to effort, and Mania was positively related to effort on one of five measures of effort. The second hypothesis was not supported.

The goal of this proposal is to design a neurobiologically-based model that describes the switching mechanism in category learning based on existing category learning theory and model. COVIS is a neurobiologically-detailed theory of multiple systems in category learning. COVIS postulates two systems that compete throughout learning—a frontal-based declarative hypothesis-testing system that uses logical reasoning and depends on working memory and executive attention, and a basal ganglia-mediated system that uses procedural learning. However, no biological mechanism has been proposed to account for the interaction between the COVIS systems. We propose a model that employs a neurobiological-based circuit that describes the interaction and switching between the hypothesis-testing system and the procedural learning systems in COVIS. With the hypothesis-testing system and procedural learning system modeled as black boxes, the model focuses on the network that facilitates switching. In COVIS, both learning systems generate a response signal in each trial based on the stimuli given. Our model incorporates the Izhikevich firing model that represents the activity of the neuronal cells from the hyperdirect pathway of the cortico-basal ganglia network. The hyperdirect pathway acts as a gate for the response signal of the procedural learning system to reach the premotor units for action selection. We propose that the procedural learning system’s response is inhibited from approaching the premotor units when the hypothesis-testing system is in control of the response. However, if rule-based strategies fail, inhibition to the procedural system’s response is reduced. The reduction in inhibition results in the acceptance of responses from both learning systems in the premotor units. To validate the proposed model, we fit the model to two groups of participants in a perceptual category-learning task. One group of participants used the optimal procedural strategy in the task and the other used a suboptimal rule-based strategy. The categorization task was an information-integration task, whereby participants had to switch away from rule-based strategies and learn to integrate the stimulus dimensions to be able to perform optimally. We were able to differentiate the switchers from the non-switchers by adjusting the parameters in the model. In addition, we fitted another task to the model in which participants from different age groups with or without Parkinson’s disease were asked to switch between rule-based and procedural strategies on a trial-by-trial basis. We were able to match the learning curve, accuracy switch cost, and proportion of switchers of the different groups of participants.

Compromised validity of test data due to exaggeration or fabrication of cognitive deficits inhibits the capacity to establish appropriate conclusions and recommendations in neuropsychological examinations. Detection of feigned neurocognitive impairment presents a formidable challenge, particularly for evaluations involving possibilities of significant secondary gain. Among specific populations examined in this domain, litigating mild traumatic brain injury (mTBI) samples are among the most researched. One subpopulation with potential to contribute significantly to this body of literature is that of retired athletes undergoing fixed-battery neuropsychological evaluations within an assessment program. Given the considerable prevalence of concussions sustained by athletes in this sport and the substantial monetary incentives within this program, a unique opportunity exists to establish rates of feigning within this population to be compared to similar forensic mTBI samples. Further, a fixed battery with multiple validity tests (VT) offers a chance to evaluate the classification accuracy of an aggregated VT failure paradigm, as uncertainty abounds regarding the optimal approach to the recommended use of multiple VTs for effort assessment. The current study seeks to examine rates of feigned neurocognitive impairment in this population, demonstrate prediction accuracy equivalence between models based on aggregated VT failures and logistic regression, and compare classification performance of various individual VTs.

The purpose of the current study was to clarify the neurocognitive mechanisms underlying social phobia. Previous research has identified some specific group differences in neurocognitive functioning between individuals diagnosed with social phobia and nonpsychiatric controls, but has failed to administer a comprehensive neuropsychological battery to a social phobia patient group, resulting in a piecemeal understanding of the neurocognitive functioning of this population and an incomplete picture of the neuropsychological profile inherent to this group. The present research utilized a broader collection of neuropsychological tests to assess nine cognitive domains: Verbal Learning, Verbal Delayed Memory, Visual Immediate Memory, Visual Delayed Memory, Visual-Spatial Processing, Verbal Working Memory, Visual Working Memory, Executive Functioning, and Attention. A mixed analysis of variance (ANOVA) did not reveal a significant group by cognitive domain interaction, nor a significant main effect of group. As this was the first study to examine multiple cognitive domains in a single sample of individuals with generalized social phobia, exploratory univariate analyses were performed to examine group differences for the specific cognitive domains. This revealed significant group differences specific to the Visual Working Memory domain, with the social phobia group scoring significantly lower than the nonpsychiatric control group. Implications of these findings and directions for future research are discussed.

Despite widespread availability of effective antiretroviral therapy (ART), people living with HIV (PWH) remain at risk of developing comorbidities including HIV-associated neurocognitive impairment (H-NCI). These individuals may then be at an increased risk for treatment non-adherence, which leads to poor quality of life and early mortality. Despite this risk, there is a paucity in trained professionals in low- and middle-income countries with appropriate knowledge and skills to identify H-NCI and make appropriate referrals for additional confirmatory testing or intervention, depending on the severity and context of the screening. General medical doctors, nurses and adherence counsellors provide most HIV related healthcare services at a primary healthcare level in South Africa. However, awareness of the clinical presentation of H-NCI, and their current screening practices among these cadres, is unclear. To address these knowledge gaps this thesis set out to explore the following aims (1) examine existing H-NCI knowledge and practices among healthcare workers delivering HIV services in South Africa, (2) develop an appropriate H-NCI training programme for primary healthcare workers, and (3) lastly, pilot the H-NCI training to determine whether H-NCI screening would be feasible at a primary healthcare level in South Africa. Methods To achieve these objectives, the study was divided into two phases. In phase one, a scoping review identified and summarised published studies addressing brain and/or behaviour training approaches, including H-NCI, targeting frontline HIV healthcare workers in Africa. An online survey was developed and administered to examine existing H-NCI knowledge and current practices among healthcare workers providing HIV services in South Africa. Focus group discussions and in-depth interviews were then conducted to explore knowledge gaps, previous H-NCI training and healthcare workers' perspectives of screening at a primary healthcare level. In phase two, an H-NCI training curriculum was developed and a work-integrated H-NCI training programme targeting primary healthcare workers was piloted. The pilot training assessed knowledge of H-NCI signs and symptoms, healthcare workers' attitude toward and comfort with H-NCI screening tools and healthcare workers ability to accurately administer an H-NCI screening tool. The assessments were repeated two months post-training to evaluate retention of knowledge and skills. Results The scoping review of the existing literature suggested that there were few brain and/ or behaviour training programs targeting healthcare workers providing HIV services in Africa. Of the ten studies identified in the scoping review, one study included H-NCI in the training curriculum. The online survey found that H-NCI knowledge was limited and screening practices virtually non-existent among healthcare workers providing HIV care in South Africa. Qualitative data gathered during the focus group discussions and the in-depth interviews provided greater insight on the existing knowledge and practices gaps as well as highlighting that healthcare workers had not received training on H-NCI. The results from the qualitative investigations showed that primary healthcare workers were in favour of receiving such training. Overall, knowledge of H-NCI improved among primary healthcare workers following the work-integrated H-NCI training programme. The training demonstrated that primary healthcare workers providing clinical services, such as medical doctors or professional nurses were able to administer an H-NCI screening tool. Although knowledge of the clinical presentation of H-NCI improved among adherence counsellors, these healthcare workers experienced challenges in administering the H-NCI screening tool. Conclusion As a body of work, the findings from this thesis suggest that healthcare professionals providing HIV services in South Africa have limited knowledge to identify H-NCI, and screening practices are uncommon. Although training revealed differences between cadres in administering screening tools, healthcare workers providing clinical care, including general medical doctors and professional nurses, may be able to provide H-NCI screening at routine annual visits. Although adherence counsellors are ideally situated in the clinic flow to provide targeted screening by flagging clinical presentation of H-NCI among PWH accessing care, this cadre will require additional training, mentorship and support to successfully administer H-NCI screening tools. However, the feasibility of H-NCI screening at a primary healthcare, timing and nature of any screening remains to be explored. This body of work is a step toward increasing the availability of skilled healthcare workers with appropriate knowledge and skills to screen and identify H-NCI in low- and middle-income countries. The work presented in this thesis provides a foundation for further development of the H-NCI training module and future investigations examining targeted screening strategies at a primary healthcare level, feasibility and access to existing interventions post-screening

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Substantial evidence emphasizing the importance of linguistic systems in reading acquisition, as well as emerging literature identifying the contribution of executive function to linguistic-based difficulties, underscores the importance of clarifying the neurocognitive mechanisms affecting reading performance. Research demonstrating the interrelationship between reading and spelling, coupled with neurocognitive theories of spelling, suggests that analysis of children’s spelling attempts may capture more subtle differences in their understanding of how to decode text. This study aimed to determine the utility of applying a spelling error analysis system as a method for differentiating between reading difficulties resulting from executive dysfunction or language deficits in a sample of children at risk for reading failure. The present study examined the relationship between executive function, language, and spelling achievement in a sample of 82 children aged 6-15 years identified as having a reading deficit and/or diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD). Hierarchical regression analyses indicated language-based skills, particularly word reading, and age significantly predicted the phonemic equivalency of misspellings. Tasks of executive functioning were not found to significantly contribute to performance on phonological spelling; however, analysis of group differences suggest that ADHD and Reading Deficit groups demonstrated unique cognitive profiles, including distinct performances on executive functioning tasks. Exploratory analyses also revealed that ADHD and Reading Deficit groups differed significantly in phonological spelling performance. Results from the current study provide evidence for the presence of two distinct underlying cognitive processes affecting spelling and, in effect, reading. Current findings have implications for the need to further examine characteristic deficits in language and executive functioning affecting children at risk for reading failure. Findings also provide support for the validity of further investigating the potential to infer differential diagnostic categories using a phonological spelling analysis. The use of an analysis of spelling errors as a diagnostic data source holds promise for a better understanding of reading failure and, ultimately, may contribute to more effective intervention practices. / text