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Boys with Attention-Deficit/Hyperactivity Disorder (ADHD) were recruited from a local neuropsychology office with controls recruited from the community to assess the relationship between prenatal androgen exposure and ADHD, as well as the possible cognitive correlates of this exposure. Putative physiological markers of prenatal androgen exposure that were measured for each child included several types of otoacoustic emissions (OAEs) as well as finger-length ratios (FLRs). Neurocognitive measures included tasks which assessed components of attention, general intelligence, reading ability, and visuospatial skills. Several other variables which may also be related to androgen exposure were included (e.g., sleep disturbance, handedness, number of older brothers) in the analyses. Children ranged in age from 7 to 12 years old with 13 controls, 19 children with ADHD/Combined Type (ADHD/C), 10 with ADHD/Inattentive Type (ADHD/IA), and an additional 11 children with ADHD/IA who were rated by their parents as having relatively high levels of an experimental construct (sluggish cognitive tempo; SCT). Because more boys than girls are diagnosed with ADHD, it was hypothesized that ADHD may be associated with prenatal masculinizing hormones (i.e., androgens), and that children with ADHD would appear more masculine on markers of androgen exposure (OAEs and FLRs) than controls. However, in our current study children with ADHD did not differ from controls on these measures. There was some evidence that children with SCT may represent a more homogenous group of children within the ADHD/IA diagnostic group, and that they may share a deficit in alerting attention. Consistent with theories suggesting subtype differences in attention, children with ADHD/C did not appear to have a deficit in alerting attention, but rather appeared more cognitively impulsive and to have a deficit in auditory attention. Children with SCT were more likely to be rated by their parents as having disrupted sleep.

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Three experiments investigated the hypothesis that high doses of methylphenidate (MPH) are particularly effective in enabling boys with Attention-Deficit Hyperactivity Disorder (ADHD) to regulate the allocafion of effort and persistence under high information processing demands. In Experiment 1, the performance of boys with ADHD, ages 7 to 13, was investigated on placebo and three dosages of MPH, on a visual-memory search (VMS) task across a wide range of processing loads. Accuracy increased with dosage in a linear fashion. Findings on reaction times (RTs) revealed, however, that MPH dosage had a differential effect depending on processing load. All doses of MPH improved accuracy on low loads without a concomitant increase in processing times. When both processing load and (MPH) dosage were high, however, the ADHD boys shifted to a more cautious, time comsuming strategy, apparently in order to achieve continuing gains in accuracy. Experiment 2 compared the performance of ADHD and control boys on the VMS. It established that the ADHD group had difficulty meeting the processing demands of the VMS across all of the information loads studied, as revealed by higher error rates and slower RTs. The ADHD-control comparison also established that the effects of high doses of MPH at high loads in Experiment 1 constituted a further slowing of the ADHD boys' already slow RTs. A third, normal developmental study of boys ages 7 to 13 showed that both error rates and RTs on the VMS task decreased with age. This study also revealed considerable similarity between the performance patterns of ADHD boys and those of younger control boys on the VMS.

The articles presented in this thesis examined issues of identification and perception of Attention Deficit Hyperactivity Disorder (ADHD) in a sample of 38 boys with ADHD and 43 comparison boys without ADHD. The boys were recruited from local schools in the Montreal area as well as through the community. In Article 1, the positive illusory bias was explored in the area of attention using two different tasks in order to improve our understanding of the self-perceptions of boys with ADHD. Some evidence for positive illusions was found in that boys with ADHD estimated performance at the same level as the comparison group despite performing significantly worse. Additionally, on the Conners' Continuous Performance Test-II (C-CPT-II), significantly more boys with ADHD overestimated their performance than comparison boys. However, because the majority of the boys underestimated their performance, it is suggested that in unfamiliar situations boys with ADHD do not exhibit positive illusions to the same extent as in familiar situations. In Article 2, the perceptions of ADHD reported by others were examined in relation to an objective measure of attention. Through this, the validity of the C-CPT-II was also examined. Parent and teacher ratings of boys with ADHD were compared to boys' performance on the C-CPT-II. Parents completed the Conners' Parent Rating Scale-Revised (CPRS-R) and the Child Behavior Checklist (CBCL) and teachers completed the Conners' Teacher Rating Scale-Revised (CTRS-R). While both parent and teacher ratings on the CPRS-R and the CTRS-R respectively showed significant correlations with performance, teachers' ratings had the highest correlations with the errors of the C-CPT-II. Only the externalizing total T score rating on the CBCL was correlated with performance on the C-CPT-II. Additionally, boys with ADHD performed significantly more poorly than comparison boys on the C-CPT-II. However, there was no significant difference between the performance of boys with ADHD and boys with learning disabilities or between boys with learning disabilities and comparison boys. Using discriminate function analysis, the C-CPT-II was able to correctly classify 72% of the participants into either an ADHD or comparison group. The final discussion centres on this research programme's contribution to the field.

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Recent genetic studies indicate an association between Attention Deficit Hyperactivity Disorder (ADHD) and the dopamine transporter gene (DAT1) with possible preferential relation to hyperactivity and impulsivity behaviours. The present study investigated attention-related behaviours in a non-clinical sample to determine whether the modulation of these behaviours is associated with genetic variability of the DAT1 within the normal population. A secondary question explored whether gender was associated with the measured attention-related behaviours. Twenty-six children were observed in the classroom during performance of independent academic work. Motor behaviours during task performance were scored using the Restricted Academic Situation Scale. Major behavioural problems were scored using the Conners' Teacher Rating Scale-Revised: Short Form (CTRS-R:S). All participants were genotyped for the DAT1. The results yielded no significant genotype group differences, although an association was found between oppositional behaviour (CTRS-R:S) and gender. These preliminary results are discussed within the current context of genetics research in ADHD.

Objective. To examine the profile of executive function (EF) performance in children diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) as function of their subtypes and comorbid disorders. Methods. Two hundred and eighteen, 6-12 year old children clinically diagnosed with ADHD were characterised according to their clinical profile. Various EF domains were assessed while children were not on medication. General cognitive performance was assessed using Wechsler Intelligence Scale for Children. Results. 54.1% of children were diagnosed with combined subtype, 34.9% with inattentive subtype and 11% with hyperactive subtype. Significant age difference was found in ADHD subtype distribution and significant age and IQ difference was found in EF performance. After controlling for age and IQ no association was found between EF and ADHD subtypes or EF and comorbid disorders. Conclusion. These results indicate that age and IQ play an important role in cognitive task performance.

This study examined three areas related to attention in primary school-aged children to answer the following questions: Are there a distinct neuropsychological differences for young children referred by teachers as lacking in attention compared to those not lacking in attention? Are there advantages to using neuropsychological measures of attention over behaviour rating scales and observations in preschool or early grade school population? Can these same neuropsychological tools evaluate the effectiveness of music with children that have attention problems? / There were 24 participants in this study, 12 children rated as having attention problems by their teacher and 12 children in the control group. Participants age ranged from 5 years 0 months to 6 years 11 months. All the children were of average intelligence, and were attending an English school or preschool within the greater Montreal Area. Participants served as their own controls for the music conditions. Participants were nested within group and order for the four treatment conditions. / Findings indicated that attention difficulties not only affect behaviour, attention, and inhibition, but also influence cognitive processes in language, memory, and visual perceptual abilities especially visual motor precision. Neuropsychological tests were useful in the assessment of children's attention difficulties and could be used to differentiate attention problems that are strictly behavioural from those that are more likely the result of neuropsychological deficits. For children with attention problems environment and music had limited effects on neuropsychological variables. Rock and roll increased children's ability to sustain visual attention if they were classified as having an attention problem. It did not have this effect for children without attention problems. Gross motor inhibition is also affected by rock and roll, but only for boys who have attention problems. Higher level interactions with gender were found in overall neuropsychological functioning and with respect to music. School based interventions must be based not only on behaviour but also on cognitive deficits; early intervention is important to this process.