This study examined processing speed and executive function late effects in survivors of pediatric ALL (hereafter referred to as Survivors). Late effects are long-term, treatment-related health problems associated with the neurotoxic side-effect of cancer treatment on brain development. Processing speed —mental and motor speed with which a person can solve nonverbal problems — was estimated via an composite of processing speed attained from several measures of processing speed. Executive function — a collection of processes orchestrated in the performance of purposeful, goal-directed behavior — was measured using the Parent and Teacher forms of the Behavior Rating Inventory of Executive Function (BRIEF). This study also explored the effect of previously identified risk factors for processing speed and executive function late effects. Finally, executive function late effects were further explored via the use of performance-based measures, including the Tower and Trail Making (Condition 4) tests of the Delis-Kaplan Executive Function System (D-KEFS). Hypotheses included (1) Survivors would demonstrate significantly poorer processing speed; (2) late effects risk factor variables (i.e., greater elapsed time since completion of treatment, lower age at diagnosis, and higher intensity of treatment) would predict poorer processing speed; (3) female gender would predict poorer processing speed; (4) parents and teachers would demonstrate both low interrater agreement (Hypothesis 4a) and differ significantly in the severity (Hypothesis 4b) of their ratings of Survivor executive function; (5) parent and teacher ratings of executive function would indicate significantly poorer Survivor metacognition (Hypothesis 5a), whereas Survivor behavioral regulation would not differ significantly (Hypothesis 5b); (6) risk factor variables would predict poorer Parent and Teacher ratings of Survivor metacognition; (7) female gender would predict poorer Parent and Teacher ratings of Survivor metacognition; (8) survivor processing speed and Parent and Teacher ratings of executive function would exhibit a positive relationship; and (9) poorer Survivor processing speed would predict poorer parent and teacher ratings of executive function. Results provided support for hypothesis 1 and 5a. Partial support was obtained for hypotheses 4a, 4b, and 7. Hypotheses 2, 3, 5b, 6, 8, and 9 were not supported. / text

The purposes of the present study were to determine which aspects of processing speed are affected in Attention-Deficit/Hyperactivity Disorder (ADHD) and which cognitive and motoric skills predict processing speed performance. Results indicated that children with ADHD performed slower than controls on perceptual and visual-motor speed measures (Symbol Search and Coding) but not on reaction time or cognitive speed measures (Simple Reaction Time and Decision Speed). Those with ADHD-PI were particularly affected. Verbal working memory predicted Symbol Search, Coding and Decision Speed performance, while graphomotor speed predicted Coding, and fine motor dexterity predicted Decision Speed. Thus, children with ADHD may struggle on tasks with greater perceptual and visual-motor demands, which may be related to the inattention dimension. Furthermore, this study provides further evidence for the relationship between working memory and processing speed, especially central executive involvement in processing speed. Other theoretical and clinical implications are discussed for classroom and clinic interventions.

Emerging research has suggested that the nature of cognitive deficits in Amnestic-MCI (a-MCI) may extend beyond memory impairments and can include deficits in attention (Gualtieri & Johnson, 2005; 2007). Recent studies have found significant differences between subjects with a-MCI and cognitively healthy individuals on measures of processing speed (Gorus, De Raedt, Lambert, Lemper, & Mets, 2008; Gualtieri & Johnson, 2005; Levinoff, Saumier, & Chertkow, 2005; Silveri et al., 2007). The current study sought to add to the limited research currently available on processing speed in a-MCI by comparing cognitively healthy individuals (M age = 64.57; SD = 6.61) and an age-matched a-MCI group (M age = 64.19; SD = 5.79) on a measure of processing speed, an index of attention. Second, the study evaluated the utility of the “25 Numbers Test” in differentiating individuals with a-MCI from a cognitively healthy group of participants. As expected, the participants with a-MCI performed more poorly (t(72) = -5.96, p < .01) on the 25 Numbers Test and demonstrated greater intra-individual variability in comparison to the cognitively healthy group (t(72) = -3.009, p < .01). The 25 Numbers Test effectively discriminated cognitively healthy individuals from those with a-MCI (AUC = 0.85, p < .01). Results will add to the limited research on processing speed in a-MCI and provide a basis for the importance of evaluating processing speed as part of routine screening for a-MCI.

This study had three main purposes. First, the relationship between Processing Speed (Gs) and poor word recognition skills was examined. Second, various formats of processing speed tests that measure different types of processing speed (i.e. naming facility, perceptual speed, semantic speed, attention and concentration) were administered to determine what aspects of Gs were more strongly correlated with word reading performance. Pearson correlations and coefficients of determination were used to evaluate the strength of the relationships and the shared variance. Third, the study sample was evaluated to determine what percentage of the poor readers participating in the study had slow processing speed.Forty-four students in grades 1-3, ages six- to ten-years old were administered the Woodcock-Johnson III Achievement reading tests of Letter-Word Identification, Reading Fluency, and Word Attack. The subjects were additionally administered the Woodcock-Johnson III Cognitive Abilities tests of Verbal Comprehension, Visual-Auditory Learning, Sound Blending, Visual Matching, Numbers Reversed, Decision Speed, Rapid Picture Naming, Pair Cancellation, and Cross Out.The results of the study indicated processing speed, as measured by the Gs Cluster score, was strongly correlated with word reading, r = .749, r2=.56. The Gs tests of Visual Matching, (r = .663, r2 = .44) and Decision Speed (r = .811, r2 = .66) were most strongly correlated with poor word reading skill. The Basic Reading Skills Cluster and the Test of Letter-Word Identification were both moderately correlated at various strengths with different formats of Gs tests. Tests of Visual Matching, Rapid Picture Naming, Pair Cancellation and Cross Out all had a moderate, significant correlation.Lastly, 47% of the poor readers (SS<85 on any of the measures of>reading) also had low Gs scores (SS<85).The results from the study demonstrate the need for further exploration of the impact of poor Gs on the development of reading skills, as well as determination of the most effective interventions for poor readers with slow processing speed.

Adult survivors of childhood posterior fossa tumors can experience reading difficulties related to white matter integrity. Previously, reading was shown to be related to cortical white matter tracts, however information transfer across the corpus callosum (CC) may also play a role in reading. The current study used both macro- and microstructural measures of the WM structure of the corpus callosum. The current study examined how white matter volume and fractional anisotropy (FA) in five divisions of the CC was related to degree of neurological risk and reading skill, and tested two mediation models predicting reading. Participants included 20 adult survivors of childhood posterior fossa tumor and 23 healthy controls. Volume and FA were measured in five divisions of the mid-sagittal corpus callosum. Total intracranial vault was used as a covariate in volume analyses. FA was reduced in CC1 and volume was reduced in each subregion in survivors. Volume but not FA was related to degree of neurological risk. Results identified that reduced volume in CC1 and CC5, and FA in CC5 appear to be specifically related to reading skill in line with the cortical reading regions that connect in these subregions of the CC. Mediation models indicate that processing speed is the mechanism by which volume is related to reading skill. These findings have implications for addressing processing speed in reading interventions in survivors and provide insight into the interhemispheric connections in the reading network.

Goal maintenance is the ability to keep task rules active in-mind so that they can guide behaviour. When this process fails, individuals are unable to use task rules appropriately, and consequently perform poorly on the given task. The rate of goal neglect has been shown to increase with the complexity of the information to be maintained, especially for those with low levels of fluid intelligence. The main aim of this thesis was to examine whether this effect arises from the limited capacity for task rules, the limited ability to cope with competition between task rules, or the limited ability to sustain maintenance of a rule over time both in younger and older adults. A second aim was to investigate whether fluid intelligence and processing speed contribute to performance when goal maintenance is taxed. In particular, the number of instructions presented at the start of the task (Experiments 1-4), the speed at which rules had to be used (Experiment 5), the infrequency with which a task-relevant goal was used relative to a task-irrelevant goal (Experiment 6), and the duration for which rules had to be maintained (Experiment 7) were manipulated. Finally, the importance of goal maintenance in a more real-world setting was examined by testing the relationship between goal neglect and academic performance in children (Experiments 8 and 9). Goal maintenance was not limited by the number of rules to be held in mind, but goal neglect did increase as the degree of competition between rules and the duration with which they were maintained increased. Fluid intelligence accounted for little of the variation in goal maintenance abilities, but processing speed played a moderating role in older adults. In terms of academic performance, goal maintenance in school-aged children significantly predicted mathematics abilities, but not language.

Converging evidence suggests that phonological awareness is at the core of reading ability. Rapid automatized naming (RAN), defined as how quickly individuals can name continuously presented familiar visual stimuli, is also known to be a strong predictor of reading performance, and reading fluency in particular. The double deficit hypothesis suggests RAN deficits represent an additional core deficit associated with the reading process. Although there are many ways to measure RAN (e.g., using letters, numbers, pictures, objects), not well established is which RAN task is most predictive of the reading fluency skills of clinic referred children. Further research is also needed to understand the relationship between RAN and general processing speed, and the extent to which RAN tasks uniquely predict the reading fluency of clinic-referred children. The purpose of the current study is to determine a) the relationships among phonemic awareness, RAN, general processing speed, and reading fluency; b) the predictive value of phonemic awareness and RAN tasks in determining reading fluency performance; c) which RAN task best predicts reading fluency; and d) if RAN tasks continue to predict reading fluency while controlling for general processing speed. 64 children from a university reading clinic were used as participants in this study. The results suggest that alphanumeric RAN task performance --and letter naming in particular-- are unique contributors to reading fluency performance in dysfluent readers. Further, the results indicate that this contribution to reading fluency extends beyond that of other theoretical components of fluency. / School of Education / School Psychology / PhD / Dissertation

Delay discounting, the belief that rewards decline in value over time, is a phenomenon observed in several clinical disorders, including Attention Deficit / Hyperactivity Disorder (ADHD), substance abuse disorders, and other impulse control disorders. Delay discounting behavior is characterized by a tendency to choose smaller, more immediate rewards over larger, more delayed rewards. This tendency has been associated with behavioral impulsivity and inability to delay gratification observed in the aforementioned clinical disorders. It has been suggested that time perception may be a salient feature of delay discounting. If the larger, longer-term reward is perceived as being more temporally remote, its relative value decreases and is associated with greater cost, and one becomes more likely to choose the more immediate reward over the longer-term (though optimal) choice. Time perception has been studied in clinical populations, with increased variability of responses as well as both under-production and overestimation of time intervals observed in those with ADHD and other disorders associated with impulsivity. The present study used informational feedback via a metronome to change belief regarding duration of a second--either increasing or decreasing it by approximately 20%. Participants were 132 college-aged students with and without a diagnosis of ADHD. Measures of impulsivity and ADHD symptomatology were collected as well, and participants completed several cognitive tasks measuring working memory and processing speed to explore the impacts of these measures on delay discounting and time perception. While participants were able to reliably incorporate the altered second belief into short estimations of time (i.e., less than a minute), the manipulation failed to generalize to longer-duration temporal estimations, and it did not affect delay discounting. Neither ADHD symptomatology, impulsivity, nor performance on the cognitive tasks were related to delay discounting behaviors, though a working memory measure was correlated with baseline (pre-manipulation) time and one longer duration estimation. This lends support to a relationship between working memory and temporal perception, though the relationship between temporal perception and delay discounting remains elusive. Directions for future studies to clarify the role of temporal processing and ADHD in delay discounting are discussed. / text

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Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prominent neurobehavioral disorders of childhood that is heavily researched and often revised. Deficits in attention/concentration, impulsivity, inhibition, information processing speed, working memory and executive functioning manifest differently according to subtype diagnosis for both children and adults. As a result, previous attempts to construct a unifying theory of ADHD with neural correlates and quantifiable performance discrepancies have resulted in a proliferation of literature reviews citing both significant and insignificant research findings. The purpose of the current study was to construct a homogenous sample of children diagnosed with ADHD and examine purported subtype differences in working memory and information processing speed using the Wechsler Intelligence Scales for Children - Forth Edition (WISC-IV). Sixty participants were selected from archival data from two clinical sites and separated into three groups according to the current DSM-IV-TR ADHD subtype criteria: ADHD Predominately Inattentive type (ADHD-IN), ADHD Predominately Hyperactive/Impulsive type (ADHD-HY), and ADHD Combined type (ADHD-C). Significant differences within groups were revealed on the Coding subtest and Processing Speed Index (PSI) relative to performance on the Perceptual Reasoning Index (PRI). No significant between groups or interaction effects were revealed. While the goal of the current study was aimed at discovering evidence of greater deficits in processing speed by the ADHD-IN group compared to the other two groups, processing speed was reduced for the entire sample providing more evidence of a possible neurological deficit/basis inherent to ADHD. The results of the current study provided minimal evidence of differences on WISC-IV measures of working memory within the current sample. The current study was successful in correcting previous methodological flaws inherent in the relevant literature by constructing a truly homogenous sample of ADHD and provided strong evidence for the necessity of an accurate diagnosis of ADHD subtypes.