This study is one of the only investigations to examine the complex inter-relationships between immune status, cognitive functioning, and disease progression in school-aged, perinatally infected, HIV+ children on HAART over time and is the first to conduct long-term follow-up assessments beyond one year after initiating HAART. Previous research has shown that HIV+ children on HAART show stability in cognitive functioning for up to one year. The current study investigated cognitive functioning, as measured by the Wechsler Intelligence Scale for Children -III, as a function of immune functioning and disease progression over time in this sample. Overall, results showed that PIQ scores remained stable over the three time points. However, further analyses demonstrated that poorer immune status, as measured by CD4% <25, at the first time point significantly predicted lower Performance IQ (PIQ)scores and PIQ subtest scores at the third time point, even after controlling for covariates. Similarly, additional analyses revealed that PIQ scores significantly declined over time as a function of CD4% category at the first time point. Finally, scores on the PIQ, Verbal IQ (VIQ), Coding, Picture Arrangement, Symbol Search, and Arithmetic at the first time point were all significant predictors of more advanced disease progression, as measured by CDC C classification at follow-up. The clinical relevance of this study and recommendations for future research in this area are discussed

Executive control allows us to ignore distraction and switch between tasks in a flexible, yet organized fashion. While a hallmark of controlled behavior, distinctions among executive control processes are not thoroughly agreed upon. The present work explored the organization of two of these executive control processes, inhibition and shifting, and their relationship to each other. There were two primary goals. The first goal was to investigate the distinction among inhibitory control processes, as “inhibition” has oftentimes been considered a unitary construct. For example, there is evidence that response-distractor inhibition, which involves resolving interference from dominant responses or distractors in the external environment, is different from resistance to proactive interference (PI), which involves overcoming interference from previously relevant representations in memory. Using aging, neuropsychology, and individual differences methodologies, I investigated the unity and diversity of inhibitory control mechanisms. The healthy aging and neuropsychological evidence supported a distinction between response-distractor inhibition and resistance to proactive interference. However, when controlling for processing speed, the individual differences work suggested a need for further specification, as only a subset of these tasks emerged in the single factor model that provided the best fit to the data. The second goal was to explore how inhibitory control processes interact with task switching, as some theoretical accounts of task switching have suggested that switch costs result from the need to overcome interference from the previously relevant task. Inconsistent with these theories, I found little relation between inhibitory control and measures of global and local task switching, and instead, working memory served as the best predictor of these shifting measures. In contrast, inhibitory control was related to the backward inhibition abilities of older adults. These findings are discussed within a theory of working memory that accounts for the patterns of results found across the different methodologies.

Executive control allows us to ignore distraction and switch between tasks in a flexible, yet organized fashion. While a hallmark of controlled behavior, distinctions among executive control processes are not thoroughly agreed upon. The present work explored the organization of two of these executive control processes, inhibition and shifting, and their relationship to each other. There were two primary goals. The first goal was to investigate the distinction among inhibitory control processes, as “inhibition” has oftentimes been considered a unitary construct. For example, there is evidence that response-distractor inhibition, which involves resolving interference from dominant responses or distractors in the external environment, is different from resistance to proactive interference (PI), which involves overcoming interference from previously relevant representations in memory. Using aging, neuropsychology, and individual differences methodologies, I investigated the unity and diversity of inhibitory control mechanisms. The healthy aging and neuropsychological evidence supported a distinction between response-distractor inhibition and resistance to proactive interference. However, when controlling for processing speed, the individual differences work suggested a need for further specification, as only a subset of these tasks emerged in the single factor model that provided the best fit to the data. The second goal was to explore how inhibitory control processes interact with task switching, as some theoretical accounts of task switching have suggested that switch costs result from the need to overcome interference from the previously relevant task. Inconsistent with these theories, I found little relation between inhibitory control and measures of global and local task switching, and instead, working memory served as the best predictor of these shifting measures. In contrast, inhibitory control was related to the backward inhibition abilities of older adults. These findings are discussed within a theory of working memory that accounts for the patterns of results found across the different methodologies.

Commonly employed executive function measures may be of limited use due to their modest ecological validity. A novel task was developed - the Multitasking in the City Test (MCT) - in an attempt to improve ecological validity. The MCT involves task demands that resemble the demands of everyday activities. In study one, healthy participants were recruited in order to explore ‘normal’ performance on the MCT and its relationship with other cognitive measures. The MCT showed poor associations with executive tests and significant correlations with non-executive tests. This suggested the MCT may evaluate executive functioning in a different way from other executive measures such that it does not simply measure component executive processes but the integration of these components into meaningful behaviour. Patients with stroke and traumatic brain injury were recruited for study two to further explore the ecological validity and MCT performance characteristics. Only the MCT and a semantic fluency task demonstrated good ecological validity via significant relationships with a behavioural rating scale. Patients and normals made qualitatively similar types of errors although patients made these errors more frequently. Patients demonstrated better planning ability but completed fewer tasks than normals on the MCT. This discrepancy was attributed to impaired initiation. In study three, the MCT and verbal fluency tasks were administered to brain-injured individuals both pre- and post-executive function rehabilitation to evaluate their utility as treatment outcome measures and to assess ecological validity via a different behavioural rating scale from the one used in study two. Strategies trained during treatment generalized to MCT but not verbal fluency performance. Both MCT and semantic fluency performance were found to have good ecological validity. Overall, the findings from this research project suggest the MCT and semantic fluency tasks have good ecological validity. They further suggest that several common executive function measures lack adequate ecological validity and may not be predictive of real world behaviour. Moreover, these results support the concept of an executive function ‘system’ that can be fractionated into a variety of executive processes and that impairments in one process (e.g., initiation) can exist alongside intact functioning in other processes (e.g., planning).

The present study examined the claim that neuropsychological deficits in set-shifting and emotional decision making are present in eating disordered patients, and to what extent these deficits relate to specific aspects of disordered eating. Sixteen eating disordered patients and 38 controls were given a battery of neuropsychological measures, as well as questionnaires measuring disordered eating. Compared to controls, patients demonstrated poorer performance on tasks of set-shifting, but not decision making, psychomotor speed, working memory, or IQ. Across groups, poor set-shifting was correlated with food-, shape-, and weight concerns, and restricting, whereas poor decision making was correlated to restricting. The study demonstrates that set-shifting deficits are present in eating disordered patients, and that specific relations exist between cognitive performance in different domains and disordered eating.

The present study examined the claim that neuropsychological deficits in set-shifting and emotional decision making are present in eating disordered patients, and to what extent these deficits relate to specific aspects of disordered eating. Sixteen eating disordered patients and 38 controls were given a battery of neuropsychological measures, as well as questionnaires measuring disordered eating. Compared to controls, patients demonstrated poorer performance on tasks of set-shifting, but not decision making, psychomotor speed, working memory, or IQ. Across groups, poor set-shifting was correlated with food-, shape-, and weight concerns, and restricting, whereas poor decision making was correlated to restricting. The study demonstrates that set-shifting deficits are present in eating disordered patients, and that specific relations exist between cognitive performance in different domains and disordered eating.

Commonly employed executive function measures may be of limited use due to their modest ecological validity. A novel task was developed - the Multitasking in the City Test (MCT) - in an attempt to improve ecological validity. The MCT involves task demands that resemble the demands of everyday activities. In study one, healthy participants were recruited in order to explore ‘normal’ performance on the MCT and its relationship with other cognitive measures. The MCT showed poor associations with executive tests and significant correlations with non-executive tests. This suggested the MCT may evaluate executive functioning in a different way from other executive measures such that it does not simply measure component executive processes but the integration of these components into meaningful behaviour. Patients with stroke and traumatic brain injury were recruited for study two to further explore the ecological validity and MCT performance characteristics. Only the MCT and a semantic fluency task demonstrated good ecological validity via significant relationships with a behavioural rating scale. Patients and normals made qualitatively similar types of errors although patients made these errors more frequently. Patients demonstrated better planning ability but completed fewer tasks than normals on the MCT. This discrepancy was attributed to impaired initiation. In study three, the MCT and verbal fluency tasks were administered to brain-injured individuals both pre- and post-executive function rehabilitation to evaluate their utility as treatment outcome measures and to assess ecological validity via a different behavioural rating scale from the one used in study two. Strategies trained during treatment generalized to MCT but not verbal fluency performance. Both MCT and semantic fluency performance were found to have good ecological validity. Overall, the findings from this research project suggest the MCT and semantic fluency tasks have good ecological validity. They further suggest that several common executive function measures lack adequate ecological validity and may not be predictive of real world behaviour. Moreover, these results support the concept of an executive function ‘system’ that can be fractionated into a variety of executive processes and that impairments in one process (e.g., initiation) can exist alongside intact functioning in other processes (e.g., planning).

The present research examined whether morphology influences word recognition independently of form-level word properties. Prevailing views attribute cross-linguistic differences in morphological processing to variations in morphological structure and/or productivity. This study tested whether morphological processing is additionally influenced by the orthographic depth of written language, by comparing primed word naming among biliterate readers of Hindu and Urdu, languages written in distinct orthographies but sharing a common morphophonology. Results from five experiments supported the view that morphological processing in orthographically shallow (transparent) Hindi script diverged significantly from that in the deeper (opaque) Urdu orthography. Specifically, morphological priming was differently affected in Hindi vs. Urdu by prim presentation conditions (Exps. 1-3): very briefly exposed (48ms), forward masked morphological primes facilitated word naming in Hindi but not in Urdu. Neither briefly presented, unmasked primes nor longer prime exposures (80ms/240ms) produced priming in Hindi, but Experiment 2 showed priming by unmasked Hindi primes at a 240 ms exposure. By contrast, Urdu exhibited morphological priming only for forward masked primes at the long exposure of 240ms. Thus, early-onset priming in Hindi resembled morpho-orthographic decomposition previously recorded in English, whereas Urdu evinced priming consistent with morpho-semantic effects documented across several languages. Hemispheric asymmetry in morphological priming also diverged across Hindi and Urdu (Exps. 4 and 5); Hindi revealed a non-significant numerical trend for facilitation by morphological primes only in the right visual field (RVF), whereas reliable morphological priming in Urdu was limited to left visual field (LVF) presentation.Disparate patterns in morphological processing asymmetry were corroborated by differences in baseline visual field asymmetries in Hindi vs. Urdu word recognition- filler words elicited a consistent RVF advantage in Hindi, whereas in Urdu, one-syllable fillers, but not two- and three-syllable words revealed the RVF advantage. Taken together, the findings suggest that the variable of orthographic depth be integrated more explicitly into mainstream theoretical accounts of the mechanisms underlying morphological processing in word recognition. In addition, this study highlights the psycholinguistic potential of the languages Hindi and Urdu for advancing our understanding of the role of orthography as well as phonology in morphological processing.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. John Patrick Kline, Florida State University, College of Arts and Sciences, School of Psychology. Title and description from dissertation home page (viewed Oct. 6, 2003). Includes bibliographical references.

The primary aim of this study was to investigate source memory performance in individuals diagnosed with Parkinson's disease (PD). The secondary goal was to explore how memory was impacted when subjects were asked to generate responses during encoding. Fifty idiopathic PD patients and fifty healthy control subjects completed a task measuring item memory and source memory which also included a generation manipulation. Relative to controls, PD patients exhibited deficits in source memory but not item memory. Both groups demonstrated enhanced memory performance in the generative condition of the item memory task. The PD group displayed a marginally significant trend toward improvement in source memory when instructed to generate a response. These findings lend support to the notion of a selective pattern of source memory impairment in PD, highlighted by a dissociation between item and source memory performance. Generative tasks may be related to increased activation of key frontal regions that facilitate memory performance. These results could inform new perspectives for cognitive rehabilitation in PD, although further research is necessary.