Effects of methylphenidate on working memory components: influence of measurement.

Author(s): Bedard AC, Jain U, Johnson SH, Tannock R

Affiliation(s): Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.

Publication date & source: 2007-09, J Child Psychol Psychiatry., 48(9):872-80.

Publication type: Research Support, Non-U.S. Gov't

BACKGROUND: To investigate the effects of methylphenidate (MPH) on components of working memory (WM) in attention-deficit hyperactivity disorder (ADHD) and determine the responsiveness of WM measures to MPH. METHODS: Participants were a clinical sample of 50 children and adolescents with ADHD, aged 6 to 16 years old, who participated in an acute randomized, double-blind, placebo-controlled, crossover trial with single challenges of three MPH doses. Four components of WM were investigated, which varied in processing demands (storage versus manipulation of information) and modality (auditory-verbal; visual-spatial), each of which was indexed by a minimum of two separate measures. RESULTS: MPH improved the ability to store visual-spatial information irrespective of instrument used, but had no effects on the storage of auditory-verbal information. By contrast, MPH enhanced the ability to manipulate both auditory-verbal and visual-spatial information, although effects were instrument specific in both cases. CONCLUSIONS: MPH effects on WM are selective: they vary as a function of WM component and measurement.