Using the Reliable Change Index Statistic to Analyze Developmental Changes in Infants at Risk for Autism Spectrum Disorder

Longitudinal studies of the development of autism spectrum disorders (ASD) provide an understanding of which variables may be important predictors of an ASD. The objective of the current study is to apply the reliable change index (RCI) statistic to examine whether the Parent Observation of Early Markers Scale (POEMS) is sensitive to developmental change, and whether these changes can be quantified along a child’s developmental trajectory. Ninety-six children with older siblings with autism were followed from 1-36 months of age. Group-based RCI analysis confirms that the POEMS is capable of detecting significant changes within pre-defined diagnostic groups. Within-subject analysis suggests that ongoing monitoring of a child at-risk for an ASD requires interpretation of both significant intervals identified by the RCI statistic, as well as the presence of repeated high (i.e., >70) scores. This study provides preliminary evidence for a reasonably sensitive and specific means by which individual change can be clinically monitored via parent report.

Emergence of normative beliefs legitimizing antisocial behaviour in adolescents : the roles of monitoring, attachment, and temperament /

Beliefs about the rightness or wrongness of engaging in various antisocial acts, referred to here as nonnative beliefs legitimizing antisocial behaviour (nblab), have been shown to playa role in the emergence oflater antisocial behaviour. The current study represented an attempt to understand whether parental monitoring and parent-child attachment have differential relationships with these antisocial nonnative beliefs in adolescents of different temperaments. The participants, 7135 adolescents in 25 high schools (ages 10- 18 years, M = 15.7) completed a wide-ranging questionnaire as part of the broad Youth Lifestyle Choices - Community University Research Alliance project, whose goal is to identify and describe the major developmental pathways of risk behaviours and resilience in youth. Two aspects of monitoring (monitoring knowledge and surveillance/tracking), attachment security, and two measures of temperament (activity level and approach) were examined for main effects and in interactions as predictors of adolescent nonnative beliefs. All of these measures were based on adolescent self-ratings on either 3- or 4-point Likert-type scales. Several important results emerged from the study. Males were higher than females in nblab; parental monitoring knowledge and adolescent attachment security were negatively related to nblab; and temperamental activity level was positively related. Monitoring knowledge, the strongest of the predictors, was much more strongly related to nonnative beliefs than was parental surveillance/tracking, supporting the contention that it is how much parents actually know, and not their surveillance efforts, that predict adolescent nonnative beliefs. A surprising finding that is of the utmost importance was that, although several of the interactions tested were significant, none were considered to be of a meaningful magnitude (defined as sr^ > .01). The current study supported the suggestion that normative beliefs legitimizing antisocial behaviour are multiply determined, and the results were discussed with respect to the observed differential relations of parental monitoring, parent-child attachment, temperament, age, and gender to antisocial normative beliefs in adolescents. Also discussed were the need to test other parenting, temperament, and other variables that may be involved in the development of nblab; the need to directly test possible mechanisms explaining the links among the variables; and the usefulness of longitudinal research in determining possible directions of causality and developmental changes in the relationships.

Charting developmental EEG gamma changes in the auditory modality /

The oscillation of neuronal circuits reflected in the EEG gamma frequency may be fundamental to the perceptual process referred to as binding (the integration of various thoughts and perceptions into a coherent picture). The aim of our study was to expand our knowledge of the developmental course ofEEG gamma in the auditory modality. 2 We investigated EEG 40 Hz gamma band responses (35.2 to 43.0 Hz) using an auditory novelty oddball paradigm alone and with a visual-number-series distracter task in 208 participants as a function of age (7 years to adult) at 9 sites across the sagital and lateral axes (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4). Gamma responses were operationally defined as change in power or a change in phase synchrony level from baseline within two time windows. The evoked gamma response was defined as a significant change from baseline occurring between 0 to 150 ms after stimulus onset; the induced gamma response was measured from 250 to 750 ms after stimulus onset. A significant evoked gamma band response was found when measuring changes in both power and phase synchrony. The increase in both measures was maximal at frontal regions. Decreases in both measures were found when participants were distracted by a secondary task. For neither measure were developmental effects noted. However, evoked gamma power was significantly enhanced with the presentation of a novel stimulus, especially at the right frontal site (F4); frontal evoked gamma phase synchrony also showed enhancement for novel stimuli but only for our two oldest age groups (16-18 year olds and adults). Induced gamma band responses also varied with task-dependent cognitive stimulus properties. In the induced gamma power response in all age groups, target stimuli generated the highest power values at the parietal region, while the novel stimuli were always below baseline. Target stimuli increased induced synchrony in all regions for all participants, but the novel stimulus selectively affected participants dependent on their age and gender. Adult participants, for example, exhibited a reduction in gamma power, but an increase in synchrony to the novel stimulus within the same region. Induced gamma synchrony was more sensitive to the gender of the participant than was induced gamma power. While induced gamma power produced little effects of age, gamma synchrony did have age effects. These results confirm that the perceptual process which regulates gamma power is distinct from that which governs the synchronization for neuronal firing, and both gamma power and synchrony are important factors to be considered for the "binding" hypothesis. However, there is surprisingly little effect of age on the absolute levels of or distribution of EEG gamma in the age range investigated.

Left ventricular structure in children with developmental coordination disorder

Developmental coordination disorder (p-DCD) is a neuro-developmental disorder featuring impairment in developing motor coordination. This study examined left ventricular mass (LVM) in children with p-DCD (n=63) and controls (n=63). LVM was measured using echocardiography. Body composition was determined using BOD POD and peak oxygen uptake (peak V02) was measured by a progressive exercise test. Height, weight and blood pressure were also measured. LVM was not significantly elevated in p-DCD compared to controls. Peak V02 was lower and SBP, BMI, HR, and BF(%) were significantly higher in p-DCD. They also demonstrated elevated stroke volume (SV), cardiac output (CO), end-diastolic volume, and ventricular diameter in diastole. In regression analyses, p-DCD was a significant predictor of SV and CO after accounting for height, FFM, V02FFM, and sex. These differences in children with p-DCD indicate obesity related changes in the left ventricle and may represent early stages of developing hypertrophy of the left ventricle.

Baroreflex sensitivity and developmental coordination disorder

Developmental coordination disorder (DCD) is a motor coordination disorder that is characterized by impairment of motor skills which leads to challenges with performing activities of daily living. Children with DCD have been shown to be less physically active and have increased body fatness. This is an important finding since a sedentary lifestyle and obesity are risk factors for cardiovascular disease. One indicator of cardiovascular health is baroreflex sensitivity (BRS), which is a measure of short term BP regulation that is accomplished through changes in HR. Diminished BRS is predictive of cardiovascular morbidity and mortality. The purpose of this study was to investigate BRS in 117 children aged 12 to 13 years with probable DCD (pOCO) and their matched controls with normal coordination. Following 15 minutes of supine rest, five minutes of continuous beat-by-beat blood pressure (Finapres) and RR interval were recorded (standard ECG). Spectral indices were computed using Fast Fourier Transform and transfer function analysis was used to compute BRS. High frequency and low frequency power spectral areas were set to 0.15-0.6 Hz and 0.04-0.15 Hz, respectively. BRS was compared between groups with an independent t-test and the difference was not significant. It is likely that a difference in BRS was not seen between groups since the difference in BMI between groups was small. As well, differences in BRS may not have manifested yet at this early age. However, the cardiovascular health of this population still deserves attention since differences in body composition and fitness were found between groups.

Developmental differences in locomotor responsiveness to amphetamine in rats

The developmental remodelling of motivational systems that underlie drug dependence and addiction may account for the greater frequency and severity of drug abuse in adolescence compared to adulthood. Recent advances in animal models have begun to identify the morphological and the molecular factors that are being remodelled, but little is known about the culmination of these factors in altered sensitivity to psycho stimulant drugs, like amphetamine, in adolescence. Amphetamine induces potent locomotor activating effects in rodents through increased dopamine release in the mesocorticolimbic dopamine system, which makes locomotor activity a useful behavioural marker of age differences in amphetamine sensitivity. The aim of the thesis was to investigate the neural basis for age differences in amphetamine sensitivity with a focus on the nucleus accumbens and the medial prefrontal cortex, which initiate and regulate amphetamine-induced locomotor activity, respectively. In study 1, I found pre- and post- pubertal adolescent rats to be less active (i.e., hypoactive) than adults to a first injection of 0.5, but not of 1.5, mg/kg of intraperitonealy (i.p.) administered amphetamine. Although initially hypoactive, only adolescent rats exhibited an increase in activity to a second injection of amphetamine given 24 h later, indicating that adolescents may be more sensitive to the rapid changes in amphetamineinduced plasticity than adults. Given that the locomotor activating effects of amphetamine are initiated in the nucleus accumbens, age differences in response to direct injections of amphetamine into this brain region were investigated in study 2. In contrast to i.p. injections, adolescents were more active than adults when amphetamine was given directly into the nucleus accumbens, indicating that hypo activity may be attributed to the development of regulatory regions outside of the accumbens. The medial prefrontal cortex (mPFC) is a key regulator of the locomotor activating effects of amphetamine that undergoes extensive remodelling in adolescence. In study 3, I found that an i.p. injection of 1.5, and not of 0.5, mg/kg of amphetamine resulted in a high expression of c-fos, a marker of neural activation, in the pre limbic mPFC only in pre-pubertal adolescent rats. This finding suggests that the ability of adolescent rats to overcome hypo activity at the 1.5 mg/kg dose may involve greater activation of the prelimbic mPFC compared to adulthood. In support of this hypothesis, I found that pharmacological inhibition of prelimbic D 1 dopamine receptors disrupted the locomotor activating effects of the 1.5 mg/kg dose of amphetamine to a greater extent in adolescent than in adult rats. In addition, the stimulation of prelimbic D 1 dopamine receptors potentiated locomotor activity at the 0.5 mg/kg dose of amphetamine only in adolescent rats, indicating that the prelimbic D1 dopamine receptors are involved in overcoming locomotor hypoactivity during adolescence. Given my finding that the locomotor activating effects of amphetamine rely on slightly different mechanisms in adolescence than in adulthood, study 4 was designed to determine whether the lasting consequences of drug use would also differ with age. A short period of pre-treatment with 0.5 mg/kg of amphetamine in adolescence, but not in adulthood, resulted in heightened sensitivity to an injection of amphetamine given 30 days after the start of the procedure, when adolescent rats had reached adulthood. The finding of an age-specific increase in amphetamine sensitivity is consistent with evidence for increased risk for addiction when drug use is initiated in adolescence compared to adulthood in people (Merline et aI., 2002), and with the hypothesis that adolescence is a sensitive period of development.

Physical Activity and Fitness in Children with Developmental Disorder

Introduction: Developmental coordination disorder (DCD) is a prevalent condition characterized by poor motor proficiency that interferes with a child‟s activities of daily living. Children with DCD often experience compromised health-related fitness components such as cardiorespiratory fitness (CRF). Purpose: To better understand the physical activity and fitness characteristics of children with probable DCD (pDCD), with a particular focus on CRF. Specifically: (1) to present a synopsis of current literature; (2) to determine the longitudinal trajectories of CRF; (3) to compare the submaximal CRF of children with and without pDCD. Methods: A comprehensive, systematic literature review was conducted of the recent available data on fitness and physical activity and pDCD (Chapter 2). This review provided the background for the other two studies included in this thesis. In Chapter 3, a prospective cohort design was used to assess how CRF in children with pDCD changes over time (56 months) relative to a group of typically developing controls. Using a nested-case control design, 63 subjects with pDCD and 63 matched controls from the larger sample were recruited to participate in the lab-based component of the study (Chapter 4). In this investigation CRF was examined using the oxygen cost of work (VO2) during an incremental test on a cycle ergometer. Results: The literature review showed that fitness parameters, including CRF and physical activity levels, were consistently reduced in children with pDCD. Chapter 3 demonstrated that the difference in CRF between children with pDCD and typically developing children is substantial, and that it tends to increase over time. Results from VO2 assessments showed that children with pDCD utilized more oxygen to sustain the same submaximal workloads compared to typically developing children. Conclusions: Findings from this thesis have made several important contributions to our understanding of children with pDCD. Since differences in CRF between children with and without pDCD tend to worsen over time, this adds to the argument that interventions intended to improve CRF may be appropriate for children with motor difficulties. This thesis also presented the first evidence suggesting that DCD involves higher energy expenditure, and could help explain why children with pDCD perform poorly on tasks requiring CRF.