Objective: Pre-school and grade-school children diagnosed with attention-deficit/hyperactivity disorder (ADHD) were compared in their performance on computerized attention tasks. Depending on the nature of the specified attention deficit, subjects were assigned to groups of cognitive subtypes. The effects of methylphenidate (MPH) were analysed depending on age and cognitive subtype.
Method: The preschool group comprised 45 children aged 5-7 years; the grade-school group comprised 54 children aged 8-12 years. Children were tested on placebo and on MPH (mean dose: 0.25-0.3 mg/kg body weight) employing tasks of alertness, sustained attention, focused attention, divided attention, and a cognitive conflict task.
Results: Both groups showed measurable attention deficits. While preschoolers were especially impaired in supervisory attention functions, grade-schoolers most frequently exhibited deficits in attention intensity and selectivity. Positive MPH effects were documented for sustained attention in both age-groups. Analysis of MPH effects in dependence on the type of attention impairment (supervisory functions vs. attention intensity/selectivity) revealed a positive relation between deficits in a specific attention domain and MPH effects.
Conclusions: Age-dependent differences in attention dysfunctions might be due to brain maturational processes. Performance on computerized attention tasks was particularly improved by MPH in children with objectified attention deficits suggesting that neuropsychological diagnostics can be useful to optimise treatment outcome.