Working Memory in children and adolescents diagnosed with AD/HD: effects of stimulant medications

Proposal details

Title: Working Memory in children and adolescents diagnosed with AD/HD: effects of stimulant medications
Research Area(s): ADHD and Allied Conditions
Background: In a previous study (in preparation), the authors reported widespread abnormalities in behavioural and ERP measures in children and adolescents diagnosed with AD/HD Predominantly Inattentive (AD/HD-in) and Combined (AD/HD-com) subtypes, from a one-back Working Memory (WM) task. Following non-target stimuli that necessitated updating task-related WM content, abnormalities were evident in the adolescent AD/HD groups at the P150 and in all groups at the P3wm. Following target stimuli, abnormalities were only seen in the AD/HD-com groups at the P150 and in the AD/HD-in groups at the P3. The most consistent results across the subtypes were decreased P3wm frontal latency to non-targets, which may reflect ineffective assimilation to new task-relevant information. In another previous study (published in the Journal of Integrative Neuroscience), the authors reported attenuated amplitude and/or decreased latency of the P3a ERP component following distracting stimuli embedded in a one-back WM task. The current study will assess whether these deficits (P150/P3/P3a) are ameliorated following the administration of stimulant medication. It will also investigate whether there are abnormalities apparent in other WM ERPs that have not been previously investigated by the authors (N1/N2), and the effects of stimulant medication on these components. This project has been approved by the AD/HD ARC-Linkage grant group.
Aims: Previous studies have reported a normalisation of electrical brain activity following the administration of stimulant medication in those diagnosed with AD/HD. In line with this, we expect the abnormalities that we have reported in the past to either (1) not be evident or (2) display a trend to normalisation.
Method: Participants will be between the ages of 6 and 17, and will include those diagnosed with the AD/HD-in and AD/HD-com according to DSM-IV-TR cirteria as well as sex- and age-matched controls. All AD/HD subjects within the database at session 1 (off medication) and 2 (on medication) are required, even if the participant has not returned for the 2nd session. This is because analyses will be carried out to ensure there were no ERP differences at baseline (session 1) between those who chose to return on-medication and those that did not.