Effects of antecedent hypoglycemia, antecedent hyperinsulinemia, and antecedent corticosterone on subsequent counterregulation in normal rats

grantor: University of TorontoThis study examined the effects of antecedent hypoglycemia, antecedent hyperinsulinemia, and antecedent increases in plasma corticosterone on subsequent counterregulatory responses to hypoglycemia in normal rats. Four days of intermittent treatment with antecedent hypoglycemia and antecedent hyperinsulinemia resulted in impaired epinephrine responses to subsequent hypoglycemia on the fifth day. This correlated with the diminished incremental increase of hepatic glucose production during the hypoglycemic clamp in these groups. Surprisingly, rats that had undergone antecedent corticosterone also displayed impaired glucose production response in spite of normal neuroendocrine counterregulation. We conclude that both antecedent hypoglycemia and antecedent hyperinsulinemia may cause defective hormonal counterregulation leading to impaired glucose production during subsequent hypoglycemia. This suggests that antecedent hyperinsulinemia 'per se' plays an important role in the pathogenesis of hypoglycemia-associated autonomic failure. Moreover, antecedent increases in corticosterone may cause deficient glucose production without altering the neuroendocrine responses to hypoglycemia, implying that other mechanisms might be involved.M.Sc

Learning to read in two languages : Chinese and English

Can children’s early reading abilities in their first language (L1) predict later literacy development in a second language (L2)? The cross-language relationships between Chinese (L1) and English (L2) among87 elementary school children in Hong Kong were explored in a longitudinal study. Chinese word reading fluency, Chinese rapid digit naming, and Chinese rhyme awareness at age 7 (Grade 1), with age and nonverbal IQ taken into account, were significant concurrent and longitudinal predictors of English word reading, and text-level reading and writing skills across ages 7 to 10. These three measures in Chinese together accounted for 16-28% of unique variance in the English literacy tasks across the three-year period. Moreover, children who showed word reading difficulties in Chinese at Grade 1 also performed significantly worse than average Chinese readers in English reading and related cognitive tasks later on, especially on phonological tasks. Results in this study provided evidence for cross-language transfer of cognitive-linguistic abilities between two distinctly different orthographies. L1 markers underlying reading difficulties in both L1 and L2 can help identify L2 learners at risk for later reading problems, even when their L2 proficiency is too limited to render proper identification. This may in turn facilitate better allocation of educational resources and targeting of early intervention programs. Based on the finding that Chinese word reading fluency was one of the strongest longitudinal predictors of English literacy development, an intervention study was conducted to explore whether repeatedly reading aloud a variety of written symbols can improve word reading fluency performance in Chinese and English. Fifty-nine Grade 2 Hong Kong Chinese children were randomly assigned to either computer-based training on repeated oral reading of digits, alphabetical letters, Chinese characters, and English words, without corrective feedback (experimental group), or online arithmetic games (control group). Reading-aloud training conducted twice a week for 7 weeks significantly improved word reading fluency in both Chinese and English, in contrast to the control group. By contrast, the experimental and control groups did not differ significantly for improvement in word reading accuracy and in the rapid naming of digits and letters. Implications for possible mechanisms underlying the observed intervention effects of repeated oral reading are discussed.published_or_final_versionPsychologyDoctoralDoctor of Philosoph

Attention-deficit/hyperactivity disorder (ADHD) in cultural context:Do parents in Hong Kong and the United Kingdom adopt different thresholds when rating symptoms, and if so why?

OBJECTIVES: Attention‐deficit/hyperactivity disorder (ADHD) prevalence is similar across world regions. However, because informants' decision thresholds may vary between regions, these similarities may mask regional variations in actual ADHD behaviours. We tested this by comparing the relationship between informant's ratings and children's measured activity in United Kingdom (UK) and Hong Kong (HK) and then explored whether any national differences in endorsement thresholds discovered are linked to cultural variations in parenting factors. METHODS: Parents rated the 18 ADHD symptoms in 112 three‐to‐five‐year‐old children stratified for ADHD symptom levels (49 girls and 63 boys; 55 from the UK and 57 from HK) and completed some parenting questionnaires. Children's task‐related activity was measured using actometers. RESULTS: In both groups, measured activity was positively correlated with hyperactivity/impulsivity (r = 0.44(HK); r = 0.41(UK)). While HK children were less active than UK children (p < 0.01), HK parents rated their children as more hyperactive/impulsive and inattentive (ps < 0.05). The lower rating threshold indicated by this pattern in HK parents were explained by their higher child‐related stress levels. CONCLUSIONS: UK and HK parents operated different ADHD symptom endorsement thresholds. The link between these and child‐related stress may mark a more general role of cultural pressure for child conformity and school achievement in HK

Do Executive Dysfunction, Delay Aversion, and Time Perception Deficit Predict ADHD Symptoms and Early Academic Performance in Preschoolers

Children with attention deficit/hyperactivity disorder (ADHD) are commonly observed to have learning difficulties. This study examined how three neuropsychological constructs—executive dysfunction, delay aversion, and time perception—were associated with ADHD symptoms and early academic performance in preschoolers at risk of ADHD. One hundred and thirty-one preschoolers (70 boys, 53%) aged 4 to 6 (M = 5.31 years) were assessed on their ADHD-related behaviors, neuropsychological functioning, word reading, and math abilities at two time points one year apart. Factor analysis indicated that inhibitory and attentional control deficit, delay aversion, and time perception/working memory deficit were three dissociable factors. Among the three factors, inhibitory and attentional control measured at Time 1 was the strongest predictor of ADHD symptoms at both Time 1 and Time 2. Time perception was closely related to working memory, and they predicted word reading and numeration across time most strongly among other neuropsychological constructs. Our findings suggested that inhibitory and attentional control, delay aversion, and time perception are dissociable neuropsychological deficits underlying ADHD symptoms in preschoolers. Poor time perception may serve as a marker for the early identification of preschoolers with potential learning problems, and a possible target of intervention for ADHD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10802-022-00937-x

An experimental task to measure preschool children's frustration induced by having to wait unexpectedly:The role of sensitivity to delay and culture

The ability to manage frustration induced by having to wait for valued outcomes emerges across childhood and is an important marker of self-regulatory capacity. However, approaches to measure this capacity in preschool children are lacking. In this study, we introduced a new task, the Preschool Delay Frustration Task (P-DeFT), designed specifically to identify children's behavioral and emotional markers of waiting-induced frustration during the imposed wait period and after the release from waiting. We then explored how waiting-induced frustration relates to individual differences in delay sensitivity and whether it differs between two cultural groups thought to have different attitudes toward children's conduct and performance: Hong Kong (HK) and the United Kingdom (UK). A total of 112 preschool children (mean age = 46.22 months) completed the P-DeFT in a quiet laboratory. Each trial had two stages; first, a button press elicited a Go signal; second, this Go signal allowed children to go to a “supermarket” to pick a target toy. On most trials, the Go signal occurred immediately on the first press. On 6 trials, an unexpected/unsignaled 5- or 10-s pre-Go-signal period was imposed. Frustration was indexed by performance (button presses and press duration), behavioral agitation, and negative affect during the pre-Go-signal wait period and the post-Go-signal shopping task. Parents rated their children's delay sensitivity. Waiting-related frustration expressed during both the pre-Go-signal wait period and the post-Go-signal task varied with (a) the length of wait and (b) individual differences in parent-rated delay sensitivity. UK children displayed more negative affect during delay than their HK counterparts, although the relationship between delay sensitivity and frustration was culturally invariant.</p