Inequality within the family (i.e. differential parenting) is associated with a variety of measures of child adjustment. To date there is no research examining the effects of this phenomenon on children’s physical health, or on the fashion in which this phenomenon may combine and interact with socioeconomic markers. The present study assessed 375 mothers and their children over a period of 18 months. Differential maternal negativity between siblings predicted change in child health, controlling for child gender, age, maternal education, income/assets, and absolute level of negativity in the household. The association between maternal education and change in child health was strongest when children were also exposed to high differential negativity, suggesting that these predictors combined in a cumulative fashion. Findings indicate that multiple forms of social disadvantage (i.e. between families and between siblings) can operate independently or in combination with one another to predict change in child health.

Inequality within the family (i.e. differential parenting) is associated with a variety of measures of child adjustment. To date there is no research examining the effects of this phenomenon on children’s physical health, or on the fashion in which this phenomenon may combine and interact with socioeconomic markers. The present study assessed 375 mothers and their children over a period of 18 months. Differential maternal negativity between siblings predicted change in child health, controlling for child gender, age, maternal education, income/assets, and absolute level of negativity in the household. The association between maternal education and change in child health was strongest when children were also exposed to high differential negativity, suggesting that these predictors combined in a cumulative fashion. Findings indicate that multiple forms of social disadvantage (i.e. between families and between siblings) can operate independently or in combination with one another to predict change in child health.

Children born prematurely exhibit a broad range of neuroanatomical abnormalities. The aim of this study was to investigate the long-term effects of very preterm birth on brain volume (cortical and subcortical), cortical thickness and surface area. The participants were 25 children born very preterm (<32 weeks gestational age) without significant post-natal medical sequelae and 32 term-born children between 7 and 10 years of age. Neuroanatomical measures were derived from an automated pipeline. The results suggest a pattern of decreased brain volume, surface area and cortical thickness for children born preterm and the relation between subcortical gray volume and total brain volume differed between groups. The cortex was significantly thinner for children born preterm than term-born children in focal regions of the parietal and temporal lobes. Therefore, even without significant postnatal medical sequelae, very preterm children still exhibit structural differences that persist into middle childhood.

Impaired social interaction is one of the hallmarks of autism spectrum disorders (ASDs). Emotional faces are arguably the most critical visual emotional stimuli and the ability to perceive, recognize, and interpret emotions is central to social interaction and communication as well as healthy development. There is however, a paucity of studies devoted to neural and cognitive mechanisms underlying emotional face processing in adolescents with ASD. Through an implicit emotional face processing task completed in the MEG, we examined spatiotemporal differences in neural activation during angry and happy emotional face processing. Results suggest atypical frontal involvement in ASD adolescents during angry and happy face processing. In particular, orbitofrontal activation in participants with ASD was found to be delayed but greater in amplitude, relative to controls.

Research suggests that brain growth follows an abnormal trajectory in children with autism spectrum disorders (ASD). A better understanding of when and how patterns of brain development diverge from that seen in typically developing children could yield insight into the etiology of the disorder, and resulting symptomatology. To investigate this hypothesis, three studies examined the relation between structural and functional brain measures and age in a group of children with an ASD, aged 6 to 14 years. Age by group interactions were found in all three studies, providing further evidence that brain development may follow an atypical trajectory in ASD. Study 1: Differences in the relation between structural indices and age were found in grey matter volume, surface area and thickness, as well as in cortical thickness of specific regions in the left inferior frontal gyrus (BA 44) and left precuneus. These measures of grey matter structure generally decreased with age in the ASD children, compared to little or no change with age in the typically developing children. Study 2: Differences in the relation between age and measures of longitudinal, radial and mean diffusivity were found in frontal, long distant, interhemispheric and posterior white matter tracts; diffusivity decreased with age in the typically developing group, but showed little or no change in the ASD group. Study 3: Differences in the relation between BOLD activation on a set-shifting task and age were found in brain regions important for cognitive flexibility, such as areas of prefrontal, right insula and parietal cortex. These effects were mainly due to decreasing activation with age for the ASD group, but increasing or no age-related change in the TD group. The findings of these three studies provide converging evidence in support of an hypothesis of dysregulated brain development in this population, which could have significant, compounding effects on the development of neural connectivity, and contribute to atypical cognitive development in children with ASD.

This study examined predictors of program participation and the potential effects of participation on child development in five school sites offering integrated preschool services as part of the Toronto First Duty (TFD) demonstration project. The TFD model offered a seamless, school-based ‘service community’ integrating childcare, kindergarten, family literacy, and other early childhood services. Despite sound conceptual arguments for the utility of integrating early childhood services, no empirical studies have examined the relation between uptake of integrated preschool services and children’s developmental outcomes, within the ecological context of integrated services. This study examined program participation levels or ‘dosage’, while considering the social ecology of the child, including family and school level characteristics that may moderate or mediate the effectiveness of community-level service integration efforts to improve child outcomes during the transition to school. The ecology of participation effects was examined through generalized linear modeling techniques analyzing a linked dataset (N=272) including: (1) systematic intake form and tracking data on hours of program use, (2) children’s school readiness or child development teacher-report ratings (Early Development Instrument) measured across five domains (physical health and well-being, social competence, emotional maturity, language and cognitive development, communication and general knowledge), and (3) a measure of service integration levels across sites. The results provided evidence that TFD achieved its outreach aims in ensuring equitable access for all families; demographic risk factors did not predict less participation in TFD integrated services. In a parallel analysis of predictors of kindergarten absences, there was one difference; males were absent more in kindergarten, whereas there were no gender differences in integrated service participation. The results provided additional evidence that the TFD model has potential in reducing disparities in children’s developmental outcomes since participation dose predicted children’s physical health and well-being, language and cognitive development, and communication and general knowledge, after taking into account demographic, parenting and site factors. Further, parents' being less child-centred and less interested in parent participation, were significant risk factors associated with children's developmental outcomes. This study has implications for understanding the ecological complexities of school readiness, and the potential processes by which program participation affects children’s outcomes.

This thesis includes four studies designed to improve the ability to predict and assess language representation in healthy children and/or individuals with neurological disorders arising in childhood. In the first study, the role of pathology type on interhemispheric plasticity of language was determined by comparing lateralization in children with developmental, acquired, and tumour pathologies. Findings from 105 consecutive intracarotid sodium amobarbital procedures were retrospectively analyzed, revealing no lateralization differences between pathology groups. In the second study, a novel verb generation paradigm and magnetoencephalography (MEG) were used to determine the spatial-temporal characteristics of language expression in healthy subjects (n = 12) and children with neurological disorders (n = 4). Time-frequency and differential beamformer analyses revealed low-beta event-related desynchronization (ERD) in the left inferior frontal lobe for verb generation. The paradigm was well-tolerated by all subjects. The third study involved assessment of expressive language lateralization in 25 healthy subjects, aged 5-18 years, using two novel MEG paradigms: covert picture naming and verb generation. Novel analyses permitted objective quantification of ERD lateralization on an individual basis. For both tasks, left lateralization of frontal lobe ERD tended to increase with advancing age. Findings suggest that adult-typical left lateralization emerges from an early bilateral language network in normal development. In the fourth study, frontal lobe ERD lateralization for naming and verb generation was characterized in 14 children and adolescents with neurological disorders. Novel analyses permitted objective assessment of individual scans at multiple contrast time windows. In several cases, rapid hemispheric shifts in predominant frontal lobe ERD were observed through the response period. On an individual basis, the assessment protocol showed promise for future use in a presurgical context. These studies serve to advance the understanding of normal paediatric language representation, and improve the ability to predict and assess language lateralization in individuals who have experienced early neurological insults.

Children at a certain age often have difficulty in flexibly shifting attention between different representational schemes. One example of such cognitive inflexibility occurs in the Dimensional Change Card Sorting (DCCS) task in which 3-year-old children have difficulty switching between sorting dimensions. For instance, after initially sorting the cards by one dimension (e.g., colour) they are unable to sort the cards by a second dimension (e.g., shape). This finding has been primarily associated with problems in attention or inhibition. The present study investigated the role of perceptual information on children’s dimensional shift abilities by manipulating the perceptual characteristics of both task-relevant (the colour or shape of the images on the cards) and task-irrelevant (the background colour or shape of the actual cards themselves) aspects of the task materials between the pre- and post-switch experimental phases. Across three experiments better performance was observed when either task-relevant or task-irrelevant information was changed, with this improved performance occurring when these changes were salient enough to induce a stimulus novelty effect. Experiment 4 investigated yet another perceptual feature of the task; the degree of stimulus realism (abstractness) on children’s cognitive flexibility. Children successfully sorted the cards when three-dimensional stimuli were used but perseverated when using two-dimensional cards, providing evidence for the role of representational status of the stimuli in influencing children’s dimensional switching. Manipulations made to increase the salience of the task material as well as those resulting in reduction of similarity between the two phases of the tasks (or increased novelty) were used to enhance children’s cognitive flexibility. Overall, these findings highlight the critical role played by the perceptual information of the overall experimental context, and have important implications for theories of cognitive flexibility.

Inhibition, an important cognitive skill relying on frontal lobe function, is often deficient in individuals with autism spectrum disorders (ASD). Spatiotemporal measures of brain activity were acquired using magnetoencephalography during a Go/No-go task with adolescents and adults with ASD and matched controls. During the task, participants responded to Go stimuli and withheld their response to No-go stimuli. Typical inhibitory network development was investigated in study 1. Adolescents displayed a distributed activity pattern, recruiting temporal and parietal regions, in addition to frontal areas, unlike adults. In study 2, inhibition was compared between individuals with and without ASD. Lateralization differences were found: adults with ASD activated the left and control adults recruited the right inferior prefrontal cortex. Adolescents with ASD recruited predominantly frontal regions, unlike their controls. Implications include immature inhibitory networks in typical adolescence and deficits in adolescents with ASD in recruiting distal cortical regions to supplement poor frontal lobe function.

Inhibition, an important cognitive skill relying on frontal lobe function, is often deficient in individuals with autism spectrum disorders (ASD). Spatiotemporal measures of brain activity were acquired using magnetoencephalography during a Go/No-go task with adolescents and adults with ASD and matched controls. During the task, participants responded to Go stimuli and withheld their response to No-go stimuli. Typical inhibitory network development was investigated in study 1. Adolescents displayed a distributed activity pattern, recruiting temporal and parietal regions, in addition to frontal areas, unlike adults. In study 2, inhibition was compared between individuals with and without ASD. Lateralization differences were found: adults with ASD activated the left and control adults recruited the right inferior prefrontal cortex. Adolescents with ASD recruited predominantly frontal regions, unlike their controls. Implications include immature inhibitory networks in typical adolescence and deficits in adolescents with ASD in recruiting distal cortical regions to supplement poor frontal lobe function.