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.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35675 |
| Date | January 1998 |
| Creators | Berman, Tamara. |
| Contributors | Douglas, Virginia I. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001659770, proquestno: NQ50112, Theses scanned by UMI/ProQuest. |
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