I. EXECUTIVE CONTROL IN EARLY CHILDHOOD.

Executive control (EC) is a central construct in developmental science, although measurement limitations have hindered understanding of its nature and development in young children, relation to social risk, and prediction of important outcomes. Disentangling EC from the foundational cognitive abilities it regulates and that are inherently required for successful executive task completion (e.g., language, visual/spatial perception, and motor abilities) is particularly challenging at preschool age, when these foundational abilities are still developing and consequently differ substantially among children. A novel latent bifactor modeling approach delineated respective EC and foundational cognitive abilities components that undergird executive task performance in a socio demographically stratified sample of 388 preschoolers in a longitudinal, cohort-sequential study. The bifactor model revealed a developmental shift, where both EC and foundational cognitive abilities contributed uniquely to executive task performance at ages 4.5 and 5.25 years, but were not separable at ages 3 and 3.75. Contrary to the view that EC is vulnerable to socio-familial risk, the contributions of household financial and learning resources to executive task performance were not specific to EC but were via their relation to foundational cognitive abilities. EC, though, showed a unique, discriminant relation with hyperactive symptoms late in the preschool period, whereas foundational cognitive abilities did not predict specific dimensions of dysregulated behavior. These findings form the basis for a new, integrated approach to the measurement and conceptualization of EC, which includes dual consideration of the contributions of EC and foundational cognitive abilities to executive task performance, particularly in the developmental context of preschool.

Developmental pathways from prenatal tobacco and stress exposure to behavioral disinhibition.

Prenatal tobacco exposure (PTE) and prenatal stress exposure (PSE) both have been linked to externalizing behavior, although their effects generally have been considered in isolation. Here, we aimed to characterize the joint or interactive roles of PTE and PSE in early developmental pathways to behavioral disinhibition, a profile of cognitive and behavioral under-control that presages severe externalizing behavior. As part of a prospective, longitudinal study, 296 children were assessed at a mean age of 5 years. Exposures were assessed via repeated interviews across the prenatal period and bioassays of cotinine were obtained. Behavioral disinhibition was assessed using temperament measures in infancy, performance-based executive control tasks and measures of disruptive and inattentive behavior. PSE was associated with a higher probability of difficult temperament in infancy. Each exposure independently predicted poorer executive control at age 5 years. Difficult temperament and executive control difficulties in turn predicted elevated levels of disruptive behavior, although links from PTE and PSE to parent-reported attention problems were less robust. Children who experienced these prenatal exposures in conjunction with higher postnatal stress exposure showed the lowest executive control and highest levels of disruptive behavior. Findings highlight the compounding adverse impact of PTE and PSE on children's behavioral trajectories. Given their high concordance, prenatal health campaigns should target these exposures in tandem.

Cognitive consequences and central nervous system injury following treatment for childhood leukemia.

OBJECTIVES: To determine the relationship between membrane damage and intellectual and academic abilities in children with acute lymphoblastic leukemia (ALL) and pilot test a math intervention for children with ALL who were affected. DATA SOURCES: Research studies and review articles. CONCLUSIONS: Despite the prophylactic central nervous system (CNS) treatment for long-term disease-free survival, many children with ALL subsequently experience declines in intellectual and academic skills. IMPLICATIONS FOR NURSING PRACTICE: Improving academic abilities in children who have received CNS treatment is of high priority and may have longlasting implications on quality of life.

Comparisons of cutoff and regression-based definitions of reading disabilities.

This study addressed the issue of specificity in reading disability by comparing two approaches to defining and selecting children with reading disabilities. One approach defined reading disability according to cutoff scores representing appropriate levels of intelligence and reading deficiency, whereas the other approach adjusted these scores for their intercorrelation through regression procedures. Results revealed clear differences in which children were identified as reading disabled according to the two definitions. However, differences in neuropsychological performance between children whose reading scores were discrepant or not discrepant with IQ were small and nonspecific for both definitions. The results of this study show that children identified as reading disabled vary according to the definition employed; at this point, there is little evidence suggesting any specificity of reading disability according to definition.

New procedures to assess executive functions in preschool children.

Executive functions are difficult to assess in preschool children, yet the preschool period is particularly important, both in the development of behavioral control and of the brain, particularly the prefrontal cortex. Several tasks were adapted from developmental and neuroscience literature and then administered to 98 preschool children (30-, 36-, 42-, 48- and 60-month age groups). Executive function task performance was related largely to age group, but not to sex or intelligence. These tasks, then, were sensitive in this age range and may be useful to delineate distinct cognitive profiles among preschool children with various neurological and developmental disorders.

Executive functioning in preschool children: performance on A-not-B and other delayed response format tasks.

The A-not-B (AB) task has been hypothesized to measure executive/frontal lobe function; however, the developmental and measurement characteristics of this task have not been investigated. Performances on AB and comparison tasks adapted from developmental and neuroscience literature was examined in 117 preschool children (ages 23-66 months). Age significantly predicted performance on AB, Delayed Alternation, Spatial Reversal, Color Reversal, and Self-Control tasks. A four-factor analytic model best fit task performance data. AB task indices loaded on two factors with measures from the Self-Control and Delayed Alternation tasks, respectively. AB indices did not load with those from the reversal tasks despite similarities in task administration and presumed cognitive demand (working memory). These results indicate that AB is sensitive to individual differences in age-related performance in preschool children and suggest that AB performance is related to both working memory and inhibition processes in this age range.

Construct validity of the Continuous Recognition Memory test.

A principal factor analysis was performed on variables derived from a neuropsychological battery administered to 100 healthy young adults in order to investigate the construct validity of the Continuous Recognition Memory test (CRM). It was hypothesized that CRM "hits" and "false alarms" would load on different factors. The factors that emerged in the analysis were labeled "Verbal Ability", "Divided Attention", "Attention to Visual Detail", "Visuomotor Integration and Planning", and "Learning and Memory". As expected, CRM hits had a significant loading on the Learning and Memory factor. However, CRM false alarms did not have a significant loading on the Divided Attention factor as expected and, instead, loaded significantly on the Attention to Visual Detail factor. A second analysis was performed using variables from the delayed condition of the memory measures. In this analysis, the CRM delayed recognition variable had significant loadings on both a "Nonverbal Memory" factor and a "Verbal Memory" factor. These analyses support the construct validity of CRM hits as a measure of learning and memory and suggest that false alarms provide a measure of attention to visual detail.

Chemotherapeutic CNS prophylaxis and neuropsychologic change in children with acute lymphoblastic leukemia: a prospective study.

OBJECTIVE: To determine whether prophylactic CNS chemotherapy for childhood acute lymphoblastic leukemia is associated with declines in neuropsychological abilities. METHODS: Growth curve analysis was used to examine neuropsychological outcome and treatment-related change in children (N = 30) who were treated at two childhood cancer centers. A comprehensive test battery was administered at baseline (8 months), 2, 3, and 4 years postdiagnosis (age at diagnosis M = 5.90 years, SD = 4.2C). RESULTS: Results indicated modest declines in arithmetic, visual motor integration, and verbal fluency. Intrathecal and systemic treatment was related to poorer visual motor integration at 4 years postdiagnosis and a faster rate of decline in visual motor integration skills across the observation period than intrathecal treatment alone. Arithmetic proficiency at 4 years after diagnosis was related to maternal education, but the rate of decline was not. Verbal fluency was unrelated to demographic or treatment variables. CONCLUSIONS: These findings suggest that neuropsychological outcome and declines are related to both demographic and treatment characteristics depending on the cognitive domain examined.